BULLETIN OF MAGNETIC RESONANCE
The Quarterly Review Journal of the • International Society of Magnetic Resonance
August 1983 Numbers 3/4
The Proceedings of The Eighth Meeting of SMA • INTERNATIONAL SOCIETY OF • MAGNETIC RESONANCE
NMR • NQR • EPR applications in Physics • Chemistry • Biology • Medicine
August 22-26, 1983 Chicago, U.S.A.
IJniveibsity of Illiiiois at CKicago BULLETIN OF MAGNETIC RESONANCE The Quarterly Review Journal of the International Society of Magnetic Resonance
Editor: DAVID G. GORENSTEIN Department of Chemistry University of Illinois at Chicago Post Office Box 4348 Chicago, Illinois, U.S.A.
Editorial Board:
E.R. ANDREW DAVID GRANT University of Florida University of Utah Gainesville, Florida, U.S.A. Salt Lake City, Utah, U.S.A.
ROBERT BLINC JOHN MARKLEY E. Kardelj University of Ljubljana Purdue University Ljubljana, Yugoslavia West Lafayette, Indiana, U.S.A.
H. CHIHARA MICHAEL PINTAR Osaka University University of Waterloo Toyonaka, Japan Waterloo, Ontario, Canada
GARETH R. EATON JAKOB SMIDT University of Denver Technische Hogeschool Delft Denver, Colorado, U.S.A. Delft, The Netherlands
DANIEL FIAT BRIAN SYKES University of Illinois at Chicago University of Alberta Chicago, Illinois, U.S.A. Edmonton, Alberta, Canada
SHIZUO FUJIWARA University of Tokyo Bunkyo-Ku, Tokyo, Japan
The Bulletin of Magnetic Resonance is a quarterly review journal sponsored by the International Society of Magnetic Resonance. Reviews cover all parts of the broad field of magnetic resonance, viz., the theory and practice of nuclear magnetic resonance, electron paramagnetic resonance, and nuclear quadrupole resonance spectroscopy including applications in physics, chemistry, biology, and medicine. The BULLETIN also acts as a house journal for the International Society of Magnetic Resonance.
CODEN:BUMRDT ISSN:0163-559X
Bulletin of Magnetic Resonance, The Quarterly Journal of the International Society of Magnetic Resonance. Copyright C 1983 by the International Society of Magnetic Resonance. Rates: Libraries and non-members of ISMAR, $50.00, members of ISMAR, $18.00. All subscriptions are for a volume year. All rights reserved. No part of this journal may be reproduced in any form, for any purpose or by any means, abstracted, or entered into any data base, electronic or otherwise, without specific permission in writing from the publisher. Council of the International Society of Magnetic Resonance DANIEL FIAT. Chairman, Chicago, Illinois, U.S.A.
MICHAEL M. P1NTAR, Secretary General and Chairman Advisory Committee on Summer Schools, Waterloo. Canada
GJ. BENE R. KOSFELD Geneva. Switzerland Dtiisburg. West Germany
R. BLINC V. J. KOWALEWSKI Ljubljana, Yugoslavia Buenos Aires. Argentina M.BLOOM D. A. LOSCHE Vancouver, Canada Leipzig. East Germany W. S. BREY P. T. NARASIMHAN Gainesville, Florida, U.S.A. Kanpur, India F. CONTI D. NORBERG Rome, Italy St. Louis, Missouri. U.S.A. J. DEPIREUX H. PFEIFER Liege. Belgium Leipzig, East Germany R. R. ERNST J. SMIDT Zurich, Switzerland Delft. The Netherlands S. FORSEN I. SOLOMON Lund, Sweden Palaiseau, France J. HENNEL 1. URSU Krakov, Poland Bucharest, Rumania 0. JARDETZKY W. von PHILIPSBORN Stanford, California, U.S.A. Ziirich. Switzerland 1. JEENER H. C. WOLF Brussels, Belgium Pfajfeinvaldring. West Germany
Honorary Council Members
E. R. ANDREW K. HAUSSER Gainesville, Florida. U.S.A. Heidelberg. West Germany F. BLOCH A. KASTLER Stanford, California, U.S.A. Paris, France
S. FUJI WAR A L. REEVES Tokyo, Japan Waterloo, Ontario, Canada H. S. GUTOWSKY Urhana, Illinois, U.S.A.
The aims of the International Society of Magnetic Resonance are to advance and diffuse knowledge of magnetic resonance and its applications in physics, chemistry, biology, and medicine, and to encourage and develop international contacts between scientists
The Society sponsors international meetings and schools in magnetic resonance and its appl'cat'ons and Puo|ishes the quarterly review journal, The Bulletin of Magnetic Resonance, the house journal of ISMAR.
The annual fee for ISMAR membership is $20 plus $18 for a member subscription to the Bulletin of Magnetic Resonance.
Send subscription to: International Society of Magnetic Resonance E207MSA University of Illinois at Chicago P.O. Box 6998, Chicago. Illinois 60680 USA ' Proceedings of the Eighth Meeting of the International Society of Magnetic Resonance August 22 • 26,1983 Chicago, Illinois, U.S.A.
GENERAL CONTENTS
Preface 92 Landmarks and Highlights of The International Society of Magnetic Resonance 93 Acknowledgments 95
National Advisory Committee, Local Organizing Committee 96 Detailed Table of Contents of Invited Talks, Short Communications, and Posters 97 Invited Talks 103 Short Communications and Posters 183 Author Index 275
Vol. 5, No. yk 91 J PREFACE
This issue of the Bulletin of Magnetic Resonance A special ISMAR Prize has been forwarded by contains manuscripts of papers to be presented at the French Embassy to Professor Anatole Abragam the Eighth Meeting of the International Society of in recognition of his outstanding contributions to the Magnetic Resonance, August 22-26,1983, Chicago, development and fundamental understanding of Illinois, U.S.A. Additional manuscripts which will be nuclear magnetism, nuclear polarization and nuclear submitted by November 1,1983 will appear in Volume ordering. 6, Issue 1, January, 1984. The program of this meeting includes the most We anticipate that about 500 scientists will par- recent advances in magnetic resonance, such as ticipate in the meeting from 27 countries including Argentina, Australia, Belgium, Brazil, Canada, China, multiple quantum spectroscopy, zero field nuclear Denmark, Federal Republic of Germany, Finland, magnetic resonance, magnetization and coherence France, India, Israel, Italy, Japan, The Netherlands, transfer, microwave induced optical nuclear polar- Norway, Poland, Romania, Scotland, South Africa, ization, magnetic resonance in incomensurate and Sweden, Switzerland, U.S.S.R., U.K., U.S.A., West chaotic systems, spin physics in disordered semi- Germany, and Yugoslavia. About 250 papers will be conductors, rotating helical magnetic ordering, presented at the meeting including 17 plenary and highly advanced studies of three dimensional struc- 48 keynote talks. Morning and afternoon sessions tures of polypeptides, studies of protein and nucleic will open with a plenary talk followed by breakouts to acids, membranes, antibodies, liquid crystals and four sessions in physics, chemistry, biology, and advances in closely related fields as laser induced medicine, each session opening with a keynote talk spin coupling phenomena, neutron magnetic followed by contributed papers. In addition, poster resonance, Geonium spectra of the finer structure sessions also divided into four sections will be held of the electron, and infrared spectra of molecular ion on Monday and Tuesday evenings, August 22 and beams at dissociation. The large number of talks in 23,1983. Following the poster sessions, space and the medical application of nuclear magnetic time will be allocated for symposia on special topics resonance is an indication of the growing impor- initiated by the participants. The opening ceremony of the meeting will take place on Monday morning, tance of this field. During the banquet dinner on August 22,1983 and will include an address by Dr. August 25,1983, Dr. Norman F. Ramsey will review Donald Langenberg, Chancellor of the University of the early history of magnetic resonance. Illinois at Chicago. Following the opening, the ISMAR Prize will be presented to Professor Brebis This meeting is the first meeting of the Inter- Bleaney in recognition of his pioneering work in national Society of Magnetic Resonance to be held developing electron spin resonance and his many in the United States of America. Previous meetings important contributions to its applications in solid in this series were held in Japan, Brazil, Australia, state physics. The Award Address will be published Israel, India, Canada, and The Netherlands. Several in Volume 6, Issue 1 of the Bulletin of Magnetic major manufacturers of magnetic resonance equip- Resonance, January, 1984. ment will have exhibits at the meeting.
Daniel Fiat August 8,1983
92 Bulletin of Magnetic Resonance Landmarks and Highlights of The International Society of Magnetic Resonance
The aims of the International Society of Magnetic Society of Magnetic Resonance was formally foun- Resonance are: to advance and diffuse knowledge ded following this meeting and its constitution adop- of Magnetic Resonance and its applications in physics, ted by its founders: Drs. E. Raymond Andrew, Robert chemistry, biology, and medicine among scientists Blinc, A. David Buckingham, Clive K. Coogan, Daniel and research institutions throughout the world, to Fiat, Shizuo Fujiwara, Karl H. Hausser, Leonard W. foster interaction among scientists in different fields Reeves and John S. Waugh. These founders formed of Magnetic Resonance, to encourage interdis- the Executive Committee. The Council consisted of ciplinary explorations, to organize schools, local the Executive Committee and the following mem- and international symposia on magnetic resonance, bers: Drs. George J. Bene, Felix Bloch, Jacques and to publish papers and periodicals on this subject. Danon, Sture Forsen, Herbert Gutowsky, Jacek Hennel, Valdemar Kowalewski, D. Artur Losche, Previous meetings were held in Tokyo, Japan, A.K. Saha, Jakob Smidt, lonel Solomon, and loan September, 1965, under the direction of Dr. Shizuo Ursu. The council recommended to hold future ISMAR Fujiwara and in Sao Paulo, Brazil, July, 1968, meetings triennially. The next meeting in Bombay, organized by Dr. Leonard W. Reeves, Dr. E. Geis- India, January, 1974, was organized by Dr. A.K. brecht, and Dr. S. Mathias. In August the following Saha. The ISMAR Award was presented to Dr. Her- year, athird conference was held in Melbourne, Aus- bert Gutowsky for his outstanding achievements in tralia, organized by Dr. Clive K. Coogan. At the clos- the field of magnetic resonance and its application ing session the participants of the meeting to chemistry. One of the major highlights of the recommended the formation of an International meeting was the presentation by Dr. Paul Lauterbur Society of Magnetic Resonance and elected Dr. of NMR Zeugmatography, which provided signifi- Daniel Fiat as Chairman for the purpose of founding cant impetus to the development of NMR Imaging. the society. In August of 1971, the Fourth Inter- The Sixth Meeting of ISMAR took place in Banff, national Symposium on Magnetic Resonance was Canada, May, 1977, and was co-chaired by Drs. held in Rehovot and Jerusalem, Israel organized by Frans H. A. Rummens and John Weil. ISMAR Awards Dr. D. Fiat. This symposium marked the 25th anniver- were presented posthumously to Dr. E. K. Zavoisky sary of the discovery of nuclear magnetic resonance. for his discovery of the electron paramagnetic Also at this meeting the First Award of the society resonance phenomenon in Kazan, U.S.S.R., in was presented to Dr. Erwin L Hahn for his discovery 1944, and also to Dr. Robert Blinc for his dis- of the spin echo phenomena and his many outstand- tinguished contribution in the applications of nuclear ing contributions to the field. The International
Vol. 5, No. 3A 93 NATIONAL ADVISORY COMMITTEE
I. M. Armitage, New Haven E. D. Becker, Bethesda J. L. Bjorkstam, Seattle T. P. Das, Albany H. G. Dehmelt, Seattle J. W. Doane, Kent G. R. Eaton, Denver J. T. Gerig, Santa Barbara D. Grant, Salt Lake City J. Hyde, Milwaukee T. L. James, San Francisco J. J. Katz, Argonne J. L. Markley, West Lafayette D. A. Netzel, Laramie R. L. Nunnally, Dallas E. Oldfield, Urbana C. P. Poole, Columbia
LOCAL ORGANIZING COMMITTEE and CO-EDITORS OF THE PROCEEDINGS
T. Brown, Urbana V. Capek, Chicago D. Fiat, Chicago D. G. Gorenstein, Chicago
Vol. 5. No. 3A 96 DETAILED TABLE OF CONTENTS OF TALKS AND POSTERS
I. MAIN TALKS PLENARY PROTEIN DYNAMICS IN THE SOLID STATE BY PROTON RELAXATION E.R. Andrew GEONIUM SPECTRA AND THE FINER STRUCTURE OF THE ELECTRON 107 H. Dehmelt, R. Van Dyck, P. Schwinberg, G. Gabrielse ROTATING HELICAL NUCLEAR MAGNETIC ORDERING 110 M. Goldman NEUTRON MAGNETIC RESONANCE 112 N. Ramsey APPLICATIONS OF DYNAMIC NUCLEAR POLARIZATION IN 13C NMR IN SOLIDS 3. Smidt, R.A. Wind, M.3. Duijvestijn SPIN PHYSICS IN DISORDERED SEMICONDUCTERS US I. Solomon
KEYNOTE - GROUP A - (PRIMARILY PHYSICS)
DIMER CREATION AND ANNIHILATION DYNAMICS IN HYDROGEN ARGON GAS MIXTURES 120 Robin L. Armstrong, Claude Lemaire INFRARED SPECTROSCOPY OF MOLECULAR IONS AT THEIR DISSOCIATION LIMITS 12* A. Carrington, R.A. Kennedy, T.P. Softley
RECENT DEVELOPMENTS IN THE THEORY OF NMR SHIFTS IN PARAMAGNETIC SYSTEMS 126 R.M. Golding, R.O. Pascual PROTON AND DEUTERON NMR IN AMORPHOUS SILICON 129 R.E. Norberg, D. J. Leopold, P.A. Fedders, 3.B. Boyce, 3.C. Knights NMR AND LIBERATIONAL TUNNELLING IN SOME AMMONIUM COMPOUNDS 133 M. Punkkinen, E.E. Ylinen, L.P. Ingman MAGNETIC RESONANCE STUDIES ON URANIUM COMPOUNDS 136 I. Ursu
KEYNOTE - GROUP B - (PRIMARILY CHEMISTRY)
MOLECULAR DYNAMICS AND STRUCTURE OF LYOTROPIC LIQUID CRYSTALS BY NMR LINE SHAPE ANALYSIS 137 G. Chidichimo, A. Golemme, 3.W. Doane
THE USE OF MIXED LIQUID CRYSTALS OF OPPOSITE DIAMAGNETIC ANISOTROPIES IN NMR 1*0 C.L. Khetrapal
LATEST RESULTS OF INDOR SPECTROSCOPY 1*3 V.J. Kowalewski MAGNETIC RESONANCE STUDIES OF SPIN DYNAMICS IN ONE-DIMENSIONAL SYSTEMS 1*6 M. Nechtschein, 3.P. Boucher, F. Devreux, F. Genoud, 3.P. Travers NMR STUDIES OF BIOLOGICAL MEMBRANES 150 3. Seelig, Francois Borle
KEYNOTE - GROUP C - (PRIMARILY BIOLOGY)
NMR STUDY OF PROTEIN SOLUTION STRUCTURES, DYNAMICS, AND CONFORMATIONAL TRANSITIONS 152 V.F. Bystrov
FLUORINE NMR SPECTROSCOPY OF PROTEINS 157 3.T. Gerig, M. Cairi, S.3. Hammond, 3.C. Klinkenborg, R.A. Nieman
31 P NMR OF NUCLEIC ACIDS 161 David G. Gorenstein
THE DYNAMIC STRUCTURE OF NUCLEIC ACIDS 165 Thomas L. 3ames, Peter Bendel, 3oe W. Keepers, 3ohn E. Taylor
Vol. 5, No. 3/1* 97 ACCESSIBILITY OF THE ACTIVE SITE IN METALLOPROTEINS TO AMBIENT WATER AS DETERMINED BY ELECTRON SPIN ECHO ENVELOPE SPECTROSCOPY W.B. Mirns, 1. Peisach, 3.L. Davis
(EYNOTE - GROUP D - (PRIMARILY MEDICINE)
CLINICAL APPLICATION OF PROTON NMR IMAGING 171 G.M. Bydder, I.R. Young INSTRUMENTATION IN NMR IMAGING 173 Lawrence E. Crooks METAL-NITROXYL INTERACTIONS. 3*. V(IV), Fe(III), Co(II), Ni(II), AND Ag(II) COMPLEXES 176 G.R. Eaton, S.S. Eaton, L. Fielding, K.M. More, R. Damoder SPIN-LABEL OXIMETRY: MEASUREMENT OF OXYGEN CONCENTRATION IN BIOLOGICAL SAMPLES 180 James S. Hyde, W.K. Subczynski, W. Froncisz, C.-S Lai
CONTRIBUTED TALKS - GROUP A - (PRIMARILY PHYSICS)
CP/MAS 13C NMR SPECTRAL EVIDENCE OF LONG-RANGE SUBSTITUENT EFFECTS IN RIGID OPIATES 184 Charles E. Brown, Sandra C. Roerig, Dames M. Fujimoto, Vern T. Burger DIPOLAR CORRELATION FUNCTIONS AND SPIN RELAXATION RATES FOR FINITE TWO-DIMENSIONAL SYSTEMS 185 3. P. Korb, H.M. McConneil ZERO-FIELD RESONANCE SPECTROSCOPY 186 S, J. Strach, R. Bra'mley EPR IN PULSED MAGNETIC FIELDS 187 3. Witters, P. de Groot, P. 3anssen, F. Herlach, G. DeVos
CONTRIBUTED TALKS - GROUP B - (PRIMARILY CHEMISTRY) NUCLEAR QUADRUPOLE PROBES OF PARAMAGNETIC MOLECULES USING ELECTRON SPIN ECHOES 188 M. K. Bowman, A. Kostka, 3.R. Norris CARBON-13 NMR STUDIES OF SOLID FORMATES AND ACETATES 189 Robin K. Harris, Christopher 3. Groombridge, Kenneth 3. Packer RELATIONSHIPS BETWEEN CARBON-13 CHEMICAL SHIFTS AND CONFORMATIONS OF OLIGOSACCHAR1DES AND 190 CELLULOSE IN THE SOLID STATE F. Horii, A. Hirai, R. Kitamaru
CONTRIBUTED TALKS - GROUP D - (PRIMARILY MEDICINE)
SAMPLE LOCALIZATION USING SURFACE COILS AND MULTIPULSE SEQUENCES FOR HIGH RESOLUTION NMR 191 M. Robin Bendall IN VIVO 31P NMR STUDIES ON EXPERIMENTAL CEREBRAL INFARCTION USING TOPICAL MAGNETIC RESONANCE (TMR) 192 K. Hirakawa, S. Naruse, Y. Horikawa, C. Tanaka, T. Higuchi, H. Nishikawa, H. Watari
POSTERS GROUP A - (PRIMARILY PHYSICS)
NEW RESULTS ON EPR STUDIES OF QUARTZ CRYSTALS 193 Harish Bahadur, R. Parshad
ANALYSIS OF NUCLEAR MODULATION AMPLITUDE IN ELECTRON SPIN ECHO SPECTROSCOPY m H. Barkhuiysen, D. van Ormondt, R. de Beer
SPIN DIFFUSION AND LONG RANGE ORDERING IN A QUASI-TWO-DIMENSIONAL MAGNETIC SYSTEM NaBp ?Te A TEMPERATURE DEPENDENT STUDY P S' E. de Boer, R. Murugesan, M.C.M. Gribnau
EPR STUDIES ON PAIRS OF 3AHN-TELLER DISTORTED HEXAKIS PYRIDINE-N-OXIDE COPPER(II) Cu(C H NO)2* IONS 196 E. de Boer, C.P. Keijzers, G. van Kalkeren, 3.S. Wood 5 5 6 THE NATURE OF THE 3AHN-TELLER EFFECT IN THE COPPER DOPED HEXAIMIDAZOLE ZINC DICHLORIDE TETRA- HYDRATE COMPLEX 197 E. de Boer, C.P. Keijzers, G. van Kalkeren, 3.S. Wood
THE EPR SPECTRA OF RARE EARTH S-STATE IONS IN GLASSY SYSTEMS 198 C. M. Brodbeck, L.E. Iton THERMAL DEGRADATION OF POLYCARBONATE-AN E.S.R. STUDY 199 M.I. Chipara, L. Georgescu, R. Georgescu, E. Barna, F. Beuran, D. Isbasescu 98 Bulletin of Maanetic Resonance DEPENDENCE OF LATTICE PARAMETER ON CRYSTAL SIZE FOR F.C.C. MATERIALS 200 L.G. Conti, B. D'Aguanno
ESR STUDY OF RADICAL PAIRS IN PHOTOLYZED R3CSH AND R3CSSH SINGLE CRYSTALS 201 M. Geoffroy, R. Franzi
INDIRECT SUPERHYPERFINE INTERACTIONS OF CATIONS WITH V-TYPE CENTERS AND TRAPPED HYDROGEN ATOMS IN HOLMIUM-EXCHANGED Y ZEOLITE 202 L.E. Iton
2 EPR STUDIES OF PHASE TRANSITIONS IN NH4Br DOPED WITH Cu * 203 Asako Kawarnori, 3. Lakshmana Rao
NEW TRENDS IN THE SPIN RELAXATION THEORY 204 R. Lenk, P. Descouts, H. Greppin
TEMPERATURE DEPENDENCE OF THE '9F NMR IN INTERCALATED ORIENTED GRAPHITES 205 K. Luders, G. Roth, H.-3. Guntherodt
ELECTRON PARAMAGNETIC RESONANCE IN CUBIC r QUARTETS 206 V. Lupei, C. Stoicescu, I. Ursu
SPIN CORRELATION FUNCTIONS IN THE WEAK EXCHANGE HEISENBERG LINEAR CHAIN BIS-(N-METHYLPHENAZINIUM) BIS^MALEODINITRILEDITHIOLATO) COPPER (II), [NMP]2 [Cu(mnt)2] .207 P.T. Manoharan, P. Kuppusamy
APPLICATIONS OF NMR AND NQR TO THE NONDESTRUCTIVE EVALUATION OF FIBER REINFORCED COMPOSITES 208 G.A. Matzkanin
THE ISOTROPY OF NONCRYSTALLINE MATERIALS AND THE EPR SPECTRA OF S-STATE IONS 209 Al. Nicula, Eleonbra Trif, S. Simon
APPLICATION OF NMR TO THE STUDY OF HYDROGEN IN INCONEL 210 A. Raizman, 3. Barak, D. Zamir, D. Eliezer
NUCLEAR SPIN-LATTICE RELAXATION IN TRANS DICHLOROETHYLENE 211 H.S. Sandhu
EPR(Cr3+) AND NMR( 27A1) STUDY OF ALUMS AT HIGH PRESSURES AND LOW TEMPERATURES 212 Shantanu Sinha, R. Srinivasan
EPR AND OPTICAL ABSORPTION STUDIES OF Ni (II) IN A TRIGONALLY DISTORTED SUBSTITUTIONAL SITE IN Zn(en)3Cl2.2H20 213 S. Subramanian, C. Muralikrishna
EPR OF Ni(I) AND Ni(III) HEXAHYDRATE COMPLEXES IN Ni(II) DOPED ZINC AND MAGNESIUM TUTION SALTS -BENT Ni-OH BONDS 21t S. Subramanian, C. Muralikrishna
EPR SPECTRA OF TETRAGONAL COPPER CENTERS IN CaO 215 J.T. Suss, 3. Barak, A. Raizman
EPR OF Fe+ TYPE CENTERS IN NaCl (Tl, Fe) CRYSTALS 216 I. Ursu, S.V. Nistor, M. Veiter-Stefanescu
ELECTRONIC STRUCTURE OF URANATE CENTERS IN ALKALI-FLUORIDES 217 I. Ursu, A. Lupei, V. Lupei
235U ENRICHMENT EFFECT IN NUCLEAR MAGNETIC RESONANCE OF 19F IN GASEOUS URANIUM HEXAFLUORIDE 218 I. Ursu, D.E. Demco, P. Fitori, M. Bogdan
2H-NMR DETERMINATION OF THE MEIER-SAUPE ORDER MATRIX IN LIQUID CRYSTALLINE PHASES 219 N.A.P. Vaz, 3.W. Doane
SPIN-LATTICE RELAXATION OF THE DIPOLAR ENERGY OF HIGHLY POLARIZED NUCLEAR SPIN SYSTEMS 220 W. Th. Wenckebach, L.3. de Haas, C.M.B. van der Zon, N.3. Poulis
DETERMINATION OF THE NUCLEAR POLARIZATION FROM THE MOMENTS OF THE NMR-LINE IN CYLINDRICAL SAMPLES 221 W.'Th. Wenckebach, C.M.B. van der Zon, P. Zonneveld, N.3. Poulis
DYNAMIC NUCLEAR POLARIZATION USING PHOTO-EXCITED PARAMAGNETIC CENTRES 222 W. Th. Wenckebach, H.W. van Kesteren, G.J. Schenk, 3. Schmidt, N.3. Poulis
NUCLEAR MAGNETIC ORDERING OF PROTON SPINS IN Ca(OH)2 AND THERMOMETRY BELOW I MICRO KELVIN 223 W. Th. Wenckebach, 3.CM. Sprenkels, N.3. Poulis
GROUP B - (PRIMARILY CHEMISTRY)
NMR STUDIES OF TETRACYANOPHENANTHROLINE COMPLEXES OF IRON (II) 22ft B.V. Agarwala, K.V. Ramanathan, C.L. Khetrapal
Vol. 5, No. 3/i» 99 NMR EVIDENCE FOR THE EXISTENCE OF A REORIENTATIONALLY DISORDERED PHASE IN MBBA 226 S. Arumugam, S.V. Bhat, R. Srinivasan 13C CHEMICAL SHIFT AS A MEASURE OF SPIROCONJUGATION EFFECT 227 Michat Batazy ELECTRON SPIN-ECHO CHARACTERIZATION OF COLLISIONS BETWEEN REACTIVE RADICALS IN SOLUTION 228 David M. Bartels, Alexander D. Trifunac, Ron G. Lawler ESR, OPTICAL AND CRYSTALLOGRAPHIC STUDIES OF DICHLORO COPPER(II) AND ZINC(II)/COPPER(H) [15-CROWN-5 ETHER]COMPLEX 229 Rene Debuyst, Fernand Dejehet, Marie Spiriet, Jean-Paul Declercq, Maurice Van Meerssche DETECTION OF INTRAMOLECULAR SUBSTITUENT INTERACTIONS IN ALIPHATIC MOLECULES BY 13C NMR SPECTRO- SCOPY 230 Helmut Duddeck ON THE STRUCTURE OF THE HYDRATED URANYL ION 231 J. Glaser, M. Aberg, D. Ferri, I. Grenthe SPIN ECHO NMR-SPECTROSCOPY FOR THE ANALYSIS OF DEUTERATED COMPOUNDS 232 H. Gunther, J.R. Wesener, P. Schmitt CP/DD/MAS CARBON-13 NMR STUDY OF NATIVE AND REGENERATED CELLULOSE 233 A. Hirai, F. Horii, R. Kitamaru NMR SPECTRA OF ORIENTED TRIMETHYL PHOSPHINE OXIDE AND SULPHIDE 23* C.L. Khetrapal, A.C. Kunwar, M.R. Lakshminarayana DETERMINATION OF INDIRECT SPIN-SPIN COUPLINGS BETWEEN HETERONUCLEI FROM NMR SPECTRA OF ORIENTED MOLECULES 235 C.L. Khetrapal, A.C. Kunwar, N. Suryaprakash
AN EPR STUDY OF THE PRIMARY RADICAL Ph2 P(O)CH2C1" OBSERVED AT 3 K ' 237 L.D. Kispert, P.-O. Samskog, CM. Arroyo, M. Geoffroy
SOLID STATE C-13 NMR STUDY OF CHAIN DYNAMICS AND MORPHOLOGY OF CRYSTALLINE POLYMERS 238 R. Kitamaru ESR LINE WIDTH AND BONDING PARAMETERS OF Cu(II)-L-ISOLEUCINE COMPLEX 239 R. Kripal, B.N. Misra RADIAL IMAGING OF POLYOXYETHYLENE MICELLES 240 Reino Laatikainen TIME RESOLVED FLUORESCENCE DETECTED MAGNETIC RESONANCE OF TRANSIENT RADICAL IONS 2*1 Steven M. Lefkowitz, Alexander D. Trifunac A SEMIQUANTITATIVE ACCOUNT FOR THE WATER 'H NMRD OF COBALT (II) PROTEINS 2*2 C. Luchinat, I. Bertini, M. Mancini, G. Spina ESR PARALLEL-EDGE LINES OF SLOW TUMBLING SPIN PROBE IN RIGID LIQUID CRYSTAL 2*3 Keiichi Ohno THE MN NUCLEAR QUADRUPOLE RESONANCE OF AZOLES AND OTHER H-BONDED SPECIES: 3OINT THEORETICAL AND EXPERIMENTAL STUDIES 2** Michael H. Palmer, John A.S. Smith CORRELATION BETWEEN ESR DETERMINED BONDING ANIJ STABILITY OF MIXED LIGAND COMPLEXES OF Cu(II) 2*5 B.S. Prabhananda ESR OF IRATI OIL SHALE KEROGEN FROM PARANA BASIN (BRASIL) 2*6
N.V. Vugman, J.J. Fernandes de Sousa, A.S. Mangrich
GROUP C - (PRIMARILY BIOLOGY)
TERTIARY STRUCTURE AND STABILITY OF THE EPIDERMAL GROWTH FACTOR 2*7 Antonio De Marco, Enea Menegatti, Mario Guarneri 13C AND 2H NMR STUDIES OF LIPIDS FROM HALOBACTERIUM CUTIRUBRUM 2*8 Irena Ekiel, G. Dennis Sprott, Harold C. Jarrell, Ian C.P. Smith STERIC INTERACTION BETWEEN THE PERIPHERAL SUBSTITUENTS OF 10(S) CHLOROPHYLL DERIVATIVES AND ITS CONFORMATIONAL CONSEQUENCES AS REVEALED BY 1H NMR SPECTROSCOPY 2*9 Paavo H. Hynninen, Simo Lotjonen ESR STUDIES ON THE MEMBRANE LIPID BILAYERS OF A MODERATELY HALOPHILIC BACTERIUM 250 Atsushi Hyono, Shigeko Kuriyama, Hisako Hara, Masamiki Masui
100 Bulletin of Magnetic Resonance 31P NMR STUDIES OF PHOSPHORYLATED DERIVATIVES OF o-CHYMOTRYPSIN 251 Deborah Kailick, Dinesh O. Shah, David G. Gorenstein
ELECTRON PARAMAGNETIC RESONANCE STUDIES ON SPIN-LABELED BOVINE BRAIN HEXOKINASE 252 U.W. Kenkare, A. Mehta, G.K. 3arori
31P NMR OF ETHIDIUM ION COMPLEXES WITH RNA MODEL SYSTEMS AND tRNAPhe 253 Kofen Lai, Evelyn M. Goldfield, David G. Gorenstein
APPLICATION OF LONG RANGE PROTON DECOUPLING TECHNIQUE TO THE ASSIGNMENT OF THE QUATERNARY CARBON SIGNALS IN THE C-13 NMR SPECTRA OF CHLOROPHYLLS AND RELATED PORPHYRINS 254 Simo Lotjonen, Paavo H. Hynninen
EPR STUDIES ON NI(II) AND CU(IQ RECONSTITUTED HEMOGLOBIN . 255 P. T. Manoharan, Kenneth D. Alston, Joseph M. Rifkind
EFFECTS OF THERMAL BLEACHING ON IRRADIATED HUMAN TOOTH ENAMEL — AN ESR STUDY 256 V.S. Murty, T.R. Kesavan
8-Z TRANSITION OF d(m5C-G-C-G-m5C-G) BY 'H-NMR SPECTROSCOPY 257 3.W. Neumann, 3. Taboury, T. Huynh-Dinh, 3. Igolen, S. Tran Dinh
CONFIGURATIONAL AND CONFORMATIONAL STUDIES OF SOME 3-ALKYL FENTANYL DERIVATIVES BY C-13 AND PROTON NMR SPECTROSCOPY - 258 F.O. Ogungbamila, A.F. Casy
13C-NMR EVIDENCE FOR THE PATHWAY OF CHLOROPHYLL BIOSYNTHESIS IN GREEN ALGA AND PHOTOSYNTHETIC BACTERIA 259 T. Oh-hama, H. Seto, S. Miyachi
FLUORINE NUCLEAR MAGNETIC RESONANCE SPECTRA OF 'TRANSITION STATE ANALOGUE' COMPLEXES OF N-ACYL-p- FLUOROPHENYLALANINALS AND a-CHYMOTRYPSIN 260 Dinesh O. Shah, David G. Gorenstein
APPLICATION OF NMR TECHNIQUES TO THE STUDY OF STEREOCHEMICAL CONTROL IN POLYKETIDE ANTIBIOTIC BIOSYNTHESIS 261 Mary M. Sherman, C. Richard Hutchinson
SODIUM-23 NMR STUDIES OF DETERGENT-MEDIATED NA+ TRANSPORT ACROSS LIPID BILAYER MEMBRANES 262 Charles S. Springer, 3r., David M. Yarmush
13-C NMR CHARACTERIZATION OF GUA/ULE RESIN COMPONENTS: GUAYULIN A AND GUAYULIN B 263 3. Visintainer, W. W. Schloman, 3r.
0-ENDORPHIN: KINETICS OF INTERCONVERSION AMONG DIFFERENT FORMS IN AQUEOUS SOLUTION 264
Lucia Zetta
GROUP D - (PRIMARILY MEDICINE)
NMR STUDIES ON THE MECHANISM OF WATER DIFFUSION THROUGH HUMAN ERYTHROCYTE MEMBRANES 265 Gh. Benga, O. Popescu, Ross P. Holmes, V.I. Pop METABOLIC ASPECTS OF LIVER REGENERATION IN RATS 266 C.A. Boicelli, A.M. Giuliani CORRELATIVE STUDY BETWEEN PROTON RELAXATION TIMES IN-VITRO AND HUMAN BRAIN TUMORS HISTOLOGY 267 3.D. de Certaines, L. Benoist, F. Darcel-Menault, M. Chatel, A.M. Bernard
'H-SPIN-K LATTICE RELAXATION TIME MEASUREMENTS IN TISSUES: EFFECT OF SURGICAL OPERATION ON T, VALUE OF RAT LIVER SAMPLES 268 A. DiNola, E. Brosio, P. Fantazzini, L. Lendinara, F. Novello
SIGNIFICANCE OF 'H-NMR RELAXATION TIME MEASUREMENT IN BRAIN EDEMA CEREBRAL INFARCTION AND BRAIN TUMORS 269 Y. Horikawa, S. Naruse, C. Tanaka, K. Hirakawa, H. Nishikawa, K. Yoshizaki
NUCLEAR MAGNETIC RELAXATION IN TISSUE: MECHANISM AND CONTRAST EFFECT 270 R. Kimmich, F. Winter
PROTON NMR VARIATIONS OF T, AND T2 IN HUMAN THYROID GLANDS DEPENDING ON THEIR HISTOLOGY 271 3.3.Lejeune, D. Beurton, A.M. Bernard, L. Benoist, G. Lancien, 3.D. de Certaines
IN VIVO 31P NMR STUDIES ON EXPERIMENTAL TUMORS USING TOPICAL MAGNETIC RESONANCE (TMR) 272 S. Naruse, Y. Horikawa, C. Tanaka, T. Higuchi, S. Ueda, K. Hirakawa, H. Nishikawa, H. Watari
PROTON NMR SPECTRA OF BRAIN TUMORS 273 C. Tanaka, S. Naruse, Y. Horikawa, K. Hirakawa, K. Yoshizaki, Y. Nishikawa
IN VIVO 31P-NMR STUDIES ON DYNAMIC CHANGES OF ENERGY METABOLITES IN RAT BRAIN DURING ANOXIA 274 Satoshi Yokono, Kenji Ogli, Atsuko Yokono, Shoji Naruse, Hiroshi Watari
Vol. 5, No. 3/4 101 BULLETIN OF MAGNETIC RESONANCE The Quarterly Review Journal of the International Society of Magnetic Resonance ORDER FORM
Vol.5 Vol.6 1983 1984 Member subscription to Bulletin of Magnetic Resonance: $18.00 Name Affiliation Non-member subscription to Bulletin of Magnetic Resonance: $50.00 Address
City State/Zip Mail form and subscription to
International Society of Magnetic Resonance • University of Illinois at Chicago • Health Sciences Center Room E207 MSA Building • Box 6998 • Chicago, Illinois 60680 • USA Editor: DAVID G. GORENSTEIN Department of Chemistry University of Illinois at Chicago Post Office Box 4348 Chicago, Illinois, U.S.A. Editorial Board:
E.R. ANDREW DAVID GRANT University of Florida University of Utah Gainesville, Florida, U.S.A. Salt Lake City, Utah, U.S.A.
ROBERT BLINC JOHN MARKLEY E. Kardelj University of Ljubljana Purdue University Ljubljana, Yugoslavia West Lafayette, Indiana, U.S.A.
H. CHIHARA MICHAEL PINTAR Osaka University University of Waterloo Toyonaka, Japan Waterloo, Ontario, Canada
GARETH R. EATON JAKOB SMIDT University of Denver Technische Hogeschool Delft Denver, Colorado, U.S.A. Delft, The Netherlands
DANIEL FIAT BRIAN SYKES University of Illinois at Chicago University of Alberta Chicago, Illinois, U.S.A. Edmonton, Alberta, Canada
SHIZUO FUJIWARA University of Tokyo, Japan Bunkyo-Ku, Tokyo, Japan
102 Bulletin of Magnetic Resonance INVITED TALKS
Vol. 5, No. l/U 103 PROTEIN DYNAMICS IN THE SOLID STATE BY PROTON RELAXATION
E.R. Andrew
Departments of Physics, Radiology and Nuclear Engineering Sciences, University of Florida, Gainesville, Florida 32611, U.S.A.
I. INTRODUCTION line dipeptides and tripeptides (6), and then to three homopolypeptides, polyala- Protein molecules have many internal nine, polyleucine and polyvaline, where degrees of freedom and their complex dy- a distribution of TC was found to charac- namical behavior may be investigated on terize the proton motions (7). Armed wi- a variety of timescales by different phy- th this knowledge of fundamental types of sical techniques. One of these is by the behavior from these simpler prototypes we measurement of proton spin-lattice re- began to examine polycrystalline proteins. laxation times Tj_ and T;jj) in the solid state, which provides information in the II. PROTEINS range 10~10s to Is. This information complements that obtained from nuclear Four proteins have been investigated relaxation measurements made in solution in polycrystalline form, namely a-chymo- and moreover relates to the environment trypsin, insulin, lysozyme and ribonucle- in which their x-ray structures were de- ase A. The proton Tj^ was measured at th- termined. ree frequencies 18, 30 and 60 MHz, from In these experiments the relaxation 300K down to 10K (8-11). The behavior of the whole dipolar-coupled proton as- for insulin is shown in fig.l. The full sembly in the solid is studied. In the lines in the figure are computer-fitted solid the framework of the protein mole- theoretical curves, fitted to the Kubo- cule remains essentially fixed in the Tomita theory (4) over the range 70-250K crystal so that the relaxation behavior assuming a log-normal distribution of cor- is directly related to intramolecular mo- relation times xc. The use of several tions; by contrast in solution these mo- measuring frequencies is vital when a tions are superimposed on the tumbling distribution of correlation times is en- of the whole molecule, which complicates countered •. Other distribution functions the relaxation analysis. Moreover in the were tried, but the log-normal distribu- solid state a much wider temperature tion fitted best. range is accessible without degradation Since we are dealing with an inhomo- of the protein, enabling better charact- geneous system with methyl and other erization of the molecular motions with groups in a wide variety of environments, activation parameters. the assumption of a distribution of To gain experience we first examined values of TC, each characterizing an ex- the family of twenty amino acids in the ponential correlation function, seems solid state (1,2,3). Analysis using the physically more appropriate than the use well-known Kubo-Tomita theory of random of a single suitably-chosen non-exponen- dipolar relaxation (4), developed from tial correlation function such as that of the original relaxation theory of Bloem- Williams and Watts (12). bergen, Purcell and Pound (5), quantita- Measured values of the dipolar relax- tively identified reorientation of meth- ation constants were in the range 1.8 to yl and NH3 groups and motions of other 3.5 x 10^ s for the four proteins. groups. At each temperature a single c- Calculation showed that methyl group re- orrelation time TC characterized each mo- orientation accounted for about 70% of tion and its temperature-variation follo- the measured relaxation constants, leav- wed a simple activation law, from which ai ing some 30% to be accounted for by side- activation energy E^ and pre-exponenti- chain motions, segmental motion, repta- al factor T0 was determined. These mea- tion and whole-body motions. As an ex- surements were extended to polycrystal- ample we note that for solid lysozyme
104 Bulletin of Magnetic Resonance T(K) T(K) 400 200 100 70 50 30 20 10 400 300 200 150 100 70 50 40 1 1 1 1 1 . • • 7 /7: • • 1-3 5 \ T, (s) f'
i 2 \ / t / • • ^N iv :' 1 r- /•• -- T,(s) / E 0.5 '-• \ /// - id2 0.2 - V'"' / 0.1 — V 5 7 10 20 30 50 100 1 1 l | l l 1 1 i 1000/T (K1) 2.5 3 5 6 7 8 9 10 20 25 Fig. 2 Proton T,D and T1 (at 18, 30 and 1000/T (K"'l f lidD l 1 Fig. 1 Proton T for solid insulin at 60 MHz) for solid lysozyme. 18 MHz(«), 30 MHz(A), 60 MHz(-). tion parameters previously determined on the basis of Tj- alone. The minimum value the median correlation time ranges from of T1T) is 210 times shorter than that of 10-10s at 250K to 4s at 50K (10). Acti- T, at 60 MHz, but theory predicts a ratio vation energies E. for the median correl- of 3000. The discrepancy is attributed ation time for the four proteins range to a spin-diffusion bottleneck (13). The from 10 to 16 kJ/mole (11). shift of the relaxation minimum to lower Systematic deviations of the exper- temperatures enables new motions to be- imental points from the theoretical come apparent above 150 K, where T-^falls curves below 60K are attributed to side- again. chain and backbone motions and non- IV. HOMOPOLYPEPTIDES classical processes (10). Deviations at the high-temperature end, between 270 We have examined poly-L-proline and and 300K arise from the motion of the polyglycine which contain no methyl small proportion of water molecules in groups and no sidechains and therefore the solid. provide a means of investigating the ef- fects of main chain motions in isolation. III. DIPOLAR RELAXATION ANS SLOW MOTIONS Polyproline showed a surprisingly strong proton relaxation with mean acti- Whereas T, provides dynamical infor- vation energy 11.7 kJ/mole (15). Analysis 10 mation in the range 10 -10 Hz, T1 of the relaxation constant showed that 1D this could be attributed to conformation- provides information in the range 1- al motion of the proline rings. Proline Hz enabling a wide range of dynamical be- ring puckering motions can therefore be havior to be covered overall. Measure- expected to contribute significantly to . ments of Tj^ were made on polycrystalline proton relaxation in proteins. a-chymotrypsin and lysozyme (13) between 10 and 300 K using the Jeneer-Broekaert By contrast the proton relaxation in three pulse sequence (14). Measured val- polyglycine is much weaker (15), arising from segmental motions of the chain which ues of TITJ for solid lysozyme are shown in Fig. 2 where measurements of T^ are modulate the dipolar interactions of the also shown for comparison. methylene and imino groups. Below 60 K The relaxation minimum of T| is shift- the relaxation of solid proteins and pol- ed about 100 K lower as predicted and yglycine tend to become equal; this sup- provided a stringent test of the activa- ports the view that segmental motions of
Vol. 5, No. 105 the protein chain make important contri- dence that it modifies the dynamical be- butions to relaxation in solid proteins havior of the proteins themselves as at low temperatures. measured by NMR. Substitution of DoO makes clear that the additional relaxa- V. WATER IN PROTEINS tion rate comes from motion of the water molecules themselves and not from changes All crystalline proteins contain some in the protein molecules. water. Our specimens were pumped at room temperature for 24 hours, and a Karl- VI. CONCLUSIONS Fischer test showed they contained about 2% water. To investigate the role and It has been possible to identify re- significance of water in the protein laxation contributions from methyl group structures, we measured Ti for two poly- reorientation, from main chain and side- crystalline proteins progressively hy- chain motions, from proline ring puckering drated up to 60% by weight of 1^0 and and from water molecules in the structure. DO (16). Results for lysozyme are snown in Fig. 3. Acknowledgements. The author is grateful TOO to his colleagues at Nottingham for their contributions to this work, especially D. 1300 —i 1 1 N. Bone, D.J. Bryant, E.M. Cashell, R. 1000 Caspar, Q.A. Meng and T.Z. Rizvi.
DRY 700 REFERENCES
500 J^E.R.Andrew,W.S.Hinshaw,M.G.Hutchins and R.O.I.Sjoblom, Molec.Phys.il 1479 (1976). T, (ms) /o''°"°~*oi\ ,jW - 2.E.R.Andrew,W.S.Hinshaw,M.G.Hutchins,R. 300 O.I.Sjoblom&P.C.Canepa,Mol.Phys.32795(76). J^E.R.Andrew,W.S.Hinshaw,M.G.Hutchins and 200 - Y//ft R.O.I.Sjoblom, Molec.Phys.34_, 1695 (1977). \f V/l/ Jj I 4_;_R.Kubo and K.Tomita, J.Phys.Soc. Japan LYSOZYME 97 888 (1954). 5.N.Bloembergen, E.M.Purcell and R.V. •i?o 100 w Pound, Phys.Rev. 23, 679 (1948). 1 1 [ 3 L 5 6 7 8 9 (i^E.R.Andrew, T.J.Green & M.J.R.Hoch, J. 1000/T (K"'i Mag.Res. 29, 33, (1978). _7^E. R.Andrew, R.Gaspar & W.Vennart, Bio- Fig. 3 Proton T, at 60 MHz for lysozyme polymers ll_, 1913 (1978). hydrated with H20 and D^O. 8^.R.Andrew, D.J.Bryant and E.M.Cashell, Chem.Phys.Lett. 69^, 551 (1980). Two main features are to be noticed. ^E.R.Andrew, D.J.Bryant, E.M.Cashell and Above 180 K increase of hydration pro- Q.A.Meng, FEBS Lett. L26, 208 (1981). gressively decreases T.. exhibiting a 10.E.R.Andrew, D.J.Bryant, E.M.Cashell & characteristic minimum which shifts to Q.A.Meng, Phys.Lett. 88A, 487 (1982). progressively lower temperatures. Below 11.E.R.Andrew,D.N.Bone,D.J.Bryant,E.M.Ca- 180 K increase of hydration progressively shell,R.Gaspar&Q.A.Meng,Pure&Appl.Chem. increases T,. 54, 585 (1982). The increased relaxation rate above Jj^G.Williams and D.C.Watts, Trans.Farad. 180K is due to reorientation of the water Soc. 66, 80 (1970). molecules. Additional water is bound 13.R.Gaspar, E.R.Andrew, D.J.Bryant and less strongly, causing the T minimum to ETM.Cashell, Chem.Phys.Lett.86^, 327(1982). shift to lower temperatures. Below 170K 14. J.Jeneer & P.Broekaert, Phys.Rev. the water molecules are effectively fro- 157, 232 (1967). zen, but they add to the proton load to 15.E.R.Andrew,D.J.Bryant,E.M.Cashell, R. be relaxed by the protein motions, caus- Gaspar&Q.A.Meng,Polymer _22_,715 (1981). ing Ti to increase with hydration. 16.E.R.Andrew,DJ.Bryant and T.Z.Rizvi, We conclude that water in polycryst- Chem.Phys.Lett. 95, 403 (1983). alline proteins contributes to their proton relaxation, but there is no evi-
106 Bulletin of Magnetic Resonance GEONIUM SPECTRA AND THE FINER STRUCTURE OF THE ELECTRON
R. Van Dyck*, P. Schwinberg*, G. Gabrielse*, H. Dehmelt*
University of Washington Department of Physics Seattle, WA 98195
The electron, taken in this a point particle characterize its charge-e and its mass mc by Dirac to possess intrinsic momentum "fi/2 and magnetic moment . 1 ing the Bohr magneton yg = efi/2moc. The latter are associated with an ir- K-lMHz-1 regular quasi-circular orbital motion of radius --n/moc at speed of light Fig. 2. Cyclotron resonance near 164 (Schrodinger's Zitter-Bewegung)(1). GHz in zero-magnetic bottle apparatus. This motibn in combination with a smal- Shown is a recorder trace of the axial ler random motion due to the zero-point frequency vs versus the cyclotron drive electromagnetic field (2) results in a frequency vca. A SO Hz shift corre- soft structure which only vaguely re- sponds to a relativistic mass increase sembles the spinning golf ball picture of ^1 ppm due to cyclotron-excitation of the elementary texts. The field of energy ^0.5 eV (9). fluctuations also produce a small ad- ditional pseudo magnetic moment ayg to light, charged quark constituents just yield the total spin magnetic moment as ys = (l+a)yg. The ratio of spin to cyclotron frequencies t + it + vs(' He )/vc( He ) = 7000
vs/vc = g/2 = US/JJB = 1+a reflects the electron constituent in ^He . Thus the close agreement of our is a sensitive structural parameter. experimental values (4,5,6) Here g is the g-factor as defined by Purcell (3) and we have used hv = 2ysB s o %g(e~) = 1.001 159 652 200 (40) and 2irvc = eBo/moc. For a proton vs/vc has the large value ^2.8 reflecting its
+ NEGATIVE CHARGE %g(e ) = 1.001 159 652 222 (50) -Q/2 ON UPPER CAP with QED theory severely constrains (7) a postulated sub-structure of e~ discus- POSITIVE CHARGE___ sed in ^100 recently reviewed papers (8) . + 0 ON RING Our measurements are performed on an ELECTRON ORBIT individual e~ almost at rest in a vz = 60 MHz Penning trap, see Fig. 1. Spin NEGATIVE CHARGE -Q/2 flips and cyclotron excitation produced ON LOWER CAP-" by rf fields at vs-vc - 166 MHz and Fig. 1. Mono-electron oscillator mode vc - 143 GHz are detected by the contin- of electron in Penning trap, the uous Stern-Gerlach effect (CSGE) (5) due Geonium "atom." In this very simple to a weak magnetic bottle causing a 1 Hz mode the electron only oscillates shift in the axial frequency vz per unit parallel to the magnetic field B and change in spin or cyclotron quantum numbers. Preliminary experiments (9) along the symmetry axis of the elec- substituting (10) the Kaufmann effect trode structure (15).
Vol. 5. No. 107 m=-l/2 In order to reduce the average axial OK., motion quantum number Tie from the 4 Kelvin equilibrium value ^1000 to ^0 I and the magnetron motion quantum number q from the initial injection value ^109 E/h to M) we use sideband cooling (5,12,16), which relies on the strong coupling of the cyclotron motion and the radiation field. For vc - 140 GHz the classical m.c2 +mahid 0 — lifetime TC for spontaneous dipole radiation is only M).l sec. This makes it possible to scatter ^1000 photons/ Fig. 3. Simplified energy level dia- sec of energy hvc for an excitation n - gram for Geonium (schematic). The five 100. Placing the electron in a node of lowest velativistic energy eigenvalues the constant amplitude standing wave are shown. Vanishing axial and magne- microwave field (5)
tron frequencies and excitations are : assumed (5). Ey = EyOsin(z/^c)sinu>ccjt= (z/-K"c)sina)cdt makes the electron which is executing a (ll)-the relativestic mass shift-for the small amplitude vibrational motion in CSGE suggest the potential for 100- the trapping well z = zosincuzt see a fold error reduction. Thus, the mass- field shift due to a strong coherent cyclotron excitation at 164 GHz to the average [cos(a) -a) )t+cos(oo -hjj )t] . level n ~ 400 has been detected as an cd z cd z axial frequency shift of ^-15 Hz, see Evidently this field does not contain Fig. 2. the carrier at the microwave generator However, the width of the resonance frequency wccj any more, but only the observed in this fashion is rauch too two side bands at u)C(j±a)z. (We use the large and more refined schemes are cur- symbols 2irv and co interchangeably ir- rently under study by us. One of these respective of subscripts.) Now by (5) attempts to detect a spin flip via choosing vC£j+vz = vc the cyclotron a relativistic frequency change of 150 motion is excited by photons whose Hz in the resolved transition between energy hvcd is by hvz too low. The the two lowest cyclotron, levels n = 0,1, photons re-emitted by the geonium atom see Fig.3, which has a natural width of in the lab frame will have frequencies ^1.5 Hz. To approach this width the vc, and also because of the Doppler axial motion must be cooled enough that effect, vc±vz, with an average energy associated random thermal relativistic close to hvc. This is by Miv higher shifts of the C ,C~ transitions do not than that of the absorbed quanta and cause excessive broadening. Further, implies that the vibrational motion to observe this one-photon transition loses hvz for each vcd photon scattered on a single (geonium) atom it is neces- or sary to use the atom itself somehow as
a low-noise amplifier, memory and read- d¥/dt = -n~/xc. out device. One way to accomplish this 2 then may be to make use of the practi- As if<*
108 Bulletin of Magnetic Resonance For the initial values k = 1000, n = H. Dehmelt enjoyed discussions with 100 assumed above TZC = 10ic =1 sec H. Lubatti, R.W. Williams, and L. Wilets, follows and k drops to 0.1 in ^9 sec in We thank the NSF for support. this very practical cooling scheme. Actually, the minimum value of k real- izable here (13,14) is REFERENCES k - n(thermal) - 0.1. (1) K. Huang, Am. Journ. of Physics jU), 479 (1952). Analogous cooling may be applied to (2) V. W. Weisskopf and T. Welton, Rev. the magnetron motion. However, here it Mod. Phys. 21^ 305 (1949). is much more effective to use axial ex- (3) J. H. Gardner and E. M. Purcell, citation at v +v to k - 5xl06 which z m Phys. Rev. 76, 1262 (1979). with an axial damping time T allows a Z (4) R. S. Van Dyck, Jr. P. Schwinberg, decrease in the magnetron quantum and H, Dehmelt, Bull. Am. Phys. number q^ with a characteristic time Soc. 24, 758 (1979). Tmz = (^/^)Tz* This works because x z (5) H. Dehmelt, in Atomic Physics 7, is reduced to ^0.05 sec by coupling to D. Kleppner and F. Pipkin, editors, a resonant LC circuit (15). For the Plenum (1981). initial values k(driven) = 5x106 set by (6) P. Schwinberg, R. S. Van Dyck, Jr., the drive power and q - 109 we have and H. G. Dehmelt, Phys. Rev. Lett. x - 10 sec and "q would drop to 106 in mz _47, 1679 (1981). 70 sec. A second step with 103-fold (7) T. Kinoshita, 5th Internat'l. Sym- power reduces q to 10 in ^0.07 sec. posium on High Energy Spin Physics, Then excitation at vc+vm for 9 sec gives Brookhaven Nat'l. Lab., Sept. 1982. "q = 0.1. (8) L. Lyons, Nuclear Physics 10, Once the (±%000) ground state has (1983). been approached it may be possible to (9) G. Gabrielse and H. G. Dehmelt, detect the C+,C~ cyclotron transitions Bull. Am. Phys. Soc. 15, 1179 by analogous side band heating. First, (1980), and to be published (1983). say for the C~ transition, weak selec- (10) H. Dehmelt, P. Ekstrom, D. Wineland v tive excitation at (C~)-v to (n) o < h and R. Van Dyck, Bull. Am. Phys. for tc - 10 sec causes ~q to grow ap- Soc. Jj^, 572 (1974). proximately linearly with time from (11) W. Kaufmann (1902), see e.g. (q)o - 1 to (q)2 = (n)otc/Tc ^ 50 trans- Richtmeyer, Kennard, and Lauritsen, fering the resonance information into "Introduction to Modern Physics," the magnetron motion radius. Then, by McGraw-Hill, New York 1955. essentially reversing the above multi- (12) H. G. Dehmelt, Nature ^62, 777 step cooling process (q)i is multiplied (1976). 7 9 by 2xl0 to (q)2 - 10 in ^80 sec. This (13) H. Dehmelt, Private communication corresponds to a macroscopic magnetron (1978). motion radius r - 0.3 mm. In turn via (14) D. J. Wineland, J. Appl. Phys. 50, the uncompensated z rH term in the trap- 2528 (1979). potential this rm-increase results in a (15) H. Dehmelt, "Stored Ion Spectrosco- detectable vz-shift. This is the final py," in "Advances in Laser Spec- signature of the sharp C~ cyclotron troscopy," F. Arecchi, D. Roess, F. resonance. Strumia, H. Walther, editors, NATO Thus, tests to 10~13 of the CPT ASI Series, Plenum, New York, 1983. mirror symmetry of e and e~ may become (16) R.S. Vandyck, Jr., P.B. Schwinberg possible. That symmetry is less than and H.G. Dehmelt in NEW FRONTIERS self-evident: in 1930-31 the negative IN HIGH ENERGY PHYSICS, Kursunoglu, energy states were identified with the Perlmutter & Scott, Ed., Plenum, proton. New York, 1978.
Vol. 5, No. 3A 109 ROTATING HELICAL NUCLEAR MAGNETIC ORDERING
M. Goldman SPSRM, CEN SACLAY 91 191 Gif-sur-Yvette Cedex, France
I. INTRODUCTION cooperative effect of the truncated dipo- lar interactions Hp, that is the effec- Nuclear dipolar magnetic ordering tive interactions in the h.otxvtinQ frame. in high field has been produced and The form of Hp depends on the rela- studied for a number of years at the tive orientations of the external field Laboratory of Nuclear Magnetism of the and the crystal axes, and the spin tem- Centre d'Etudes Nucleaires de Saclay(l). perature can be chosen positive or nega- Nuclear magnetic ordering differs tive. This double freedom allows the widely from the magnetic ordering of production of a whole series of different electronic spins in several respects : orderings in the same crystal. An exten- - The nature of the spin-spin interac- sive description of the investigation by tions is different : they are long ran- NMN and neutron diffraction of several ge dipole-dipole interactions for nu- ordered structures is given in Ref.(l). clear spins whereas electronic spins For all these structures, ferro or anti- usually experience short range Heisen- ferromagnetic, the spins are oriented berg interactions. along the external field, and these struc- - The magnetic moments and spin-spin ture look the same in the laboratory as interactions are very much weaker for in the rotating frame. nuclear spins than for electronic spins, The work described in this article, with the result that the critical tempe- performed in collaboration with C.URBINA, rature for magnetic transition is excee- J.F.JACQUINOT and A.ABRAGAM, concerns a dingly low, in the yK range, and the structure of a different nature : the bulk nuclear magnetizations are hardly orientations of the spins are perpendi- measurable by static methods. cular to the external field HQ. They - The nuclear spin-lattice relaxation form a helix whose pitch, parallel to HQ, times at low lattice temperature are is much larger than the interatomic dis- very long ; for macroscopic times, nu- tance (2). It is only in the rotating clear spin systems are isolated systems frame that this structure looks static. which can be submitted to the various Viewed from the laboratory frame, the manipulations available from Spin Tempe- spins are precessing around Ho at the rature theory. Larmor frequency, with constant relati- The production of nuclear magnetic ve orientations. The existence of a ma- ordering occurs in two successive steps: gnetic ordering in the form of a stable a dynamic polarization through off- macroscopic coherent superposition of resonance microwave irradiation of quantum states is a novelty, unknown in paramagnetic impurities, which decreases electron magnetism. the nuclear Zeeman entropy, followed by an ADRF, that is a fast passage stop- II. THEORETICAL PREDICTION AND EXPERI- ped at resonance, which imparts this MENTAL INVESTIGATION OF THE TRANSVERSE low entropy to the truncated dipolar HELIX interactions. At sufficiently low entro- py, that is high initial nuclear polari- The system under study is the simple sation prior to the ADRF, the nuclear cubic system of 1"F spins in CaF2- The spin system undergoes a transition to sample is a sphere of 110 Bulletin of Magnetic Resonance , . . 2+ . vanishing transverse dipolar field produ- polarization are Tin ions at a concen- ced by its neighbors. This rotating trans- tration of ~ 1.5x 10~5. The external verse dipolar field plays the same role field is 2.7 T and the lattice tempera- as an appLLed rf field in the spin-lock ture of 0.27 K is produced by pumped case, and is expected to show up by an liquid helium 3. effective-frequency dependence of the The ADRF is produced at positive polarization rate of the spins S analo- spin temperature with the external field gous to that in the spin-lock case. HQ oriented in the vicinity of a three- fold symmetry axis of the crystal. This is indeed what is observed : The local Weiss field approximation, when the 19p spins are demagnetized from which neglects short range correlations, an initial polarization p^ =* 0.8, the predicts two degenerate ordered struc- polarization function f ((i)e) of 43ca has tures : a longitudinal ferromagnet with a sharp maximum for a ^^ca effective domains in the form of thin slices paral- field of 27 G, and a half width at half lel to H , and a transverse helix of intensity of about 8 G. It is possible o to refine the analysis of the I-S ther- wave vector k, parallel to Ho and small: \h\ « a » where a is the lattice para- mal mixing by describing the variation metre. of the 19p dipolar energy in terms of This degeneracy is lifted by spin- creation and annihilation of elementary wave corrections in favor of the helical excitations, within the approximation structure. RPA (Random Phase Approximation). The The most direct evidence for the agreement with the experimental shape of transverse nature of the ordering is the function f(we), for several orienta- obtained by studying the rate of polari- tions of the external field Ho, is qua- zation of the rare isotope ^Qa. by ther- litative . mal mixing with the '°p reservoir in the Other substances are expected on rotating frame, in the presence of an theoretical grounds to give rise to trans- rf irradiation close to the 43ca Larmor verse nuclear ordering. They are at pre- frequency. This is best understood by sent under active investigation. reference to the studies of thermal mi- REFERENCES xing between abundant spins I and rare spins S at high spin temperature (3). (1) A.ABRAGAM and M.GOLDMAN, Nuclear The salient results of these studies Magnetism : Order and Disorder are the following : (Oxford University Press, 1982) - The rate of polarization of the spins ch.8. S is of the form : (2) C.URBINA, J.F.JACQUINOT and M.GOLDMAN, W = sin29 f(w ) Phys.Rev.Lett. _48, 206 (1982). e where 8 is the angle between the exter- (3) D.A.Mc ARTHUR, E.L.HAHN and R.WALSTEDT, nal field and the effective field seen Phys.Rev. 188, 609 (1969). by the spins S in the rotating frame, and ue their Larmor frequency in this effective field. - When the secular dipolar reservoir is cooled by an ADRF on the spins I, the function f (we) is a monotonic decreasing function of toe. - When the spins I are spin-locked in the rotating frame the functions f(ue) is maximum when the Hartmann-Hahn condi- tion is fulfilled : equal effective fre- quencies for the spins I and S. When at low entropy the ADRF of the spins I produces a transverse ordering, each spin I is ordered along the non- Vol. 5, No. 3A 111 NEUTRON MAGNETIC RESONANCE Norman F. Ramsey Harvard University Cambridge, Massachusetts 02138 I. INTRODUCTION sonance pattern is studied by observing the detected neutron intensity as a func- Neutron magnetic resonance provides tion of the oscillator frequency. In an effective means for studying the this form the apparatus provides a mea- limit to the neutron electric dipole as surement of the neutron magnetic moment a test of time reversal symmetry. It if the magnetic field is calibrated. To also provides a measurement of the neu- detect the presence of a neutron elec- tron magnetic moment. The method has tric dipole moment, an electric field is also been adapted to measuring for added successively parallel and antipar- the first time parity non-conserving allel to the static magnetic field and rotation of the neutron when it passes the shift in the resonance frequency is through various substances. observed. These experiments (2) have set a limit to the electric dipole mo- II. NEUTRON ELECTRIC DIPOLE MOMENT ment yr divided by the proton charge e of E Limits to the neutron electric dipole moment have been set by the neutron beam 6x10 25cm (1) experiments of Dress et al (1) and by magnetic resonance experiments with III. NEUTRON MAGNETIC MOMENT bottled neutrons by Altarev et al (2) at Lenningrad and by the Harvard-Sussex The neutron beam magnetic resonance -Rutherford-ILL collaboration (3) at apparatus at Grenoble has also been used Grenoble. by Greene, et al (4) to determine the The most recent experiments (2,3) magnetic moment u of the neutron. The have utilized neutrons whose velocities neutron resonance frequency was measured are less than 6 m/s and which are there- as the neutrons passed through a glass by totally reflected from certain sur- tube between two separated but coherent faces such as Be and BeO. Such neutrons oscillatory fields. The magnetic field are transmitted through totally reflect- was calibrated by the proton resonance ing neutron pipes to a magnetized thin for flowing water passing through the foil which transmits neutrons of one same tube. In terms of the nuclear spin polarization only. These polarized magneton vu the result (4) is neutrons are admitted to a cylindirical neutron bottle which is then closed. The neutrons are subjected to a weak = 1.91304308(54) (2) static magnetic field and two short pulsed oscillatory fields at the neu- IV. PARITY NON-CONSERVING SPIN ROTATIONS tron resonance frequency, one just after the bottle is closed and the other just The possibility of observable parity before it is opened. The neutrons then non-conserving spin rotation due to the go back through the magnetized foil weak interaction for neutrons passing which now serves as an analyzer for through various media was suggested changes in the orientation of the neu- long ago by F.C. Michel (5) and L. tron spin. The neutrons that success- Stodolsky (6), but for many years the fully pass through the analyzer are rotations were thought to be too small counted and the neutron magnetic re- to be observable. However, Forte, 112 Bulletin of Magnetic Resonance Heckel and their associates (7,8) 1. W.B. Dress, et al Phys Rev. DL5, 9 devised an apparatus that is very sen- (1977) sitive to the spin orientation of the 2. I.S. Altarev, et al Phys. Lett. 102B, neutron. With this apparatus such spin 13(1981) rotations have been seen for the first 3. N.F. Ramsey, Ann.Rev.Nucl.Part.Sc.32, time and the spin rotation angle 124 Sn : -0.4811.49 50 Natural5?La :-219±14 NaturalQOPb : +2.24±0.33 Vol. 5, No. 3A 113 APPLICATIONS OF DYNAMIC NUCLEAR POLARIZATION IN 13C NMR IN SOLIDS R.A.Wind, M.J.Duijvestijn and J.Smidt Department of Applied Physics, Delft University of Technology P.O.Box 5046, 2600 GA Delft, The Netherlands I. INTRODUCTION (ii) the Solid State effect occurs in solids containing fixed paramagnetic Recently it has been shown (1,2,3) centra.Then due to the time-indepen- that in coal, a material which by na- dent nucleus-electron dipolar inter- ture contains many free electrons,the actions the normally forbidden tran- 13C signal can be enhanced by one or sition probability W' between levels two orders, of magnitude by means of with an energy difference h(d)g+u)j) the Dynamic Nuclear Polarization (DNP) becomes nonzero.Pj is antisymmeetri- technique, hence by irradiating at or cal around Wg and becomes optimal near the electron Larmor frequency.In when (jO=tOg+(jjj.In most practical cases 13 this way a C spectrum could be mea- W'<< W-j- and (^i)max can be approxi- sured in a few minutes or less.In this mated by l+g(W'/WI) (cog/to-,-) , where paper some new results on coal will be 6=± 1 for OJ=(jOg+co-j-. W-j- is the nuclear given as well as applications of DNP relaxation rate. in other solids containing free elec- (iii) the Thermal Mixing effect oc- trons, namely diamonds and undoped curs in case of large concentrations trans-polyacetylene. of fixed paramagnetic centra,where Three mechanisms can be responsible the electron-electron dipolar inter- for the DNP effect, namely the Over- actions become non-negligible.Then hauser, the Solid State and the Ther- irradiation near Wg enhances the po- mal Mixing effect (4-6). Which of the- larization of the electronic dipolar se mechanisms is present in a material system (7) and via electron nucleus depends on the type of nucleus-elec- dipolar interactions this enhance- tron interaction His, its time-depen- ment is transferred to the nuclear dence and the number of free electrons: Zeeman system. P-j- is anti-symmetri- (i) the Overhauser effect occurs when cal again around U)=a)g, and becomes Hjg,which may be scalar and/or dipo- optimal when (i)=us±Ao), where Ao) often lar, is time-dependent with a rate is of the order of half the line- comparable to the electron Larmor fre- width of the ESR line.At infinite quency wg.Then relaxation transitions microwave power (Pj)max can be app- 1 are present due to which a.o. a nu- roximated by 1+0.5 6 WIg(Wx+WIs)'" clear and an electron spin flip si- (tog/Aw) ,where 6=± 1 for (JJ=0)S+AU). Wjg multaneously. The nuclear signal en- is the rate of energy transfer from hancement Pj becomes optimal when ir- the nuclear Zeeman system to the lo- radiating with a frequency a)=Wg,and cal system. lies between +(JL>C/U)T (pure scalar in- teractions) and -\ Wg/ooj (pure dipo- II. APPLICATIONS OF DNP IN 13, lar interactions,extreme narrowing SPECTROSCOPY limit). u is the nuclear Larmor fre- quency. In practice these limits are All measurements are performed at often less,depending on the used mi- room temperature in an external mag- crowave power and the nuclear relax- netic field of 1.4T,corresponding to ation rate in absence of the free a 13C frequency of 15 MHz, a lU fre- electrons. quency of 60 MHz and a microwave fre— 114 Bulletin of Magnetic Resonance quency of 40 GHz. The nicroTT.ive power 3.1. Coal incident on the cavity was ^ g^ j^e experimental set-up is described else- Fig.l shows the XH enhancement P» 13 where (8), In principle the C signal 13 and the C enhancement Pc as a func- can be enhanced in two ways: (i) direct- tion of the microwave frequency OJ of l3 ly, and measuring the (decoupled) C a low volatile bituminous coal with a free induction decay after a 90 rf volatile matter percentage of 20%. It pulse (the DNP-FID experiment). As the follows that PH is governed by all DNP enhancement depends on the position three DNP mechanisms with the solid of the C atom with respect to the state effect as the dominating one(at i3 electrons mainly the C atoms close least at the used value of the micro- to the electrons are observed, (ii) in- wave power.Pc is probably governed by directly?by enhancing an abundant spin both the solid state and the thermal system,if present,and transferring this mixing effect.It was found that both enhanced polarization towards the 13C PJJ and Pc decrease with decreasing spins via cross-polarization (the DNP- coal rank,and become fyl for volat. CP experiment).Due to the spin diffu- matt, percentages >45%.Hence DNP can sion among the abundant spins a more be applied in higher coal ranks only. uniform enhancement can be expected. Fig.2 shows the 13C FID and CP spectra of the same coal,measured with and without DNP. 13C FID JCCP 1 : EXPERIMENTAL NA = 22,500 / /\ NA=20,000 2: SOLID STATE = 10 SEC / 1 DL = 0.6SEC MT = 62HR / \MT=3 HR _10 3. THERMAL MIXING 4:OVERHAUSER r 13C DNP-FID /N A 13CDNP-CP N A NA=100 (W-W )/2w (MHz) NA = 10 / s DL =30SEC / \DL =0.6 SEC MT = 5 MIN / \MT = 1 MIN \ / -200 0 -200 0 PPM (from TMS) Fig.2.13C FID and CP spectra of a low volatile bituminous coal, mea- sured with and without DNP. Also given are the number of acquisi- tions (NA),the delay time between ac- quisitions (DL) and the total measu- ring time (MT).The differences in MT with and without DNP are conclusive. An extensive treatment of the results will be published elsewhere. 3.2. Diamonds In diamonds the unpaired electrons may be supplied by nitrogen impurities Fig.l, P and FQ as a function of OJ of (9). Fig.3 shows the 13C DNP-FID spec- a low volatile bituminous coal. trum of an industrial diamond. The en- Vol. 5, No. 115 hancement Pc is caused by the solid Industrial diamonds may also contain state effect and estimated to be %100. ferromagnetic impurities,which can broaden both the ESR and 13C line considerably.The result may be an un- resolved solid state effect (fig.4a) DIAMOND(16000 SERIES) and a * 3C spectrum is measured,which 13 C DNP-FID is distorted because Pc varies over NA=1 the spectrum, see fig.4b.The maximum DL = 0.5HR value of Pc is estimated to be a few hundred. 3.3. Poly-acetylene In undoped trans-(CH)X at 9 GHz a positive Overhauser effect has been 100 0 100 reported (10).We found a similar re- PPM (from TMS) sult at 40 GHz (fig.5) indicating Fig.3.The 13C DNP-FID spectrum of an industrial diamond (16000 series), 1,3: ESR LINE ._• A 2:PC-1 4000 PPM A v -10 -50 0 50 Fig.5.Pfl of undoped trans-(CH)X as a function of co WS/2JT»40GHZ 0Jc/2it=15MHz that the mobility of the solitons b C DNP-FID | must be at least of the order of 1 1 13 O)S=2.5 lO ^- . Fig.6 shows the CP, DNP-CP and DNP-FID spectra of trans- 4000; PPM (CH)X. Apart from the considerable reduc- tion in measuring time due to DNP we observe that the shape of the spectra are all different,indicating that even -4000 4000 -4000 4000 for the protons the DNP enhancement is PPM not uniform over the sample.Probably (U)-U)s)/2jt=-120MHz (U)-U)s)/2n=+120MHz the 13C DNP-FID spectrum reflects best the chains containing a soliton.The reason for the spectral changes is still under investigation. Fig.4a: The ESR line effects and Pc as Concluding we can say that DNP can a function of u) of an industri- be used as an important tool to reduce al diamond (de Beer's SDA-rlOOS). measuring times of l3C spectra in so- P is obtained by subtracting lids.This can be applied both in so- curve 3 from 1; lids containing free radicals by na- i3 4b: The C DNP-FID spectrum,obtain ture and in solids doped with a sta- ned for different offsets 0)-0)g. ble radical (8).Also magic angle spin- 116 Bulletin of Magnetic Resonance REFERENCES 1. R.A.Wind, J.Trommel and J.Smidt, 13C CP SPECTRUM Fuel _58_, 900, 1979 2. R.A.Wind, M.J.Duijvestijn, J.Smidt NA = 20.000 and J.Trommel, Proc.Int.Conf. on DL = 0.2 SEC Coal Science, 812 (Verlag Gliick- MT = 4000 SEC auf GmbH, Essen 1981) 3. R.A.Wind, J.Trommel and J.Smidt, Fuel 6J_, 398, 1982 4. A.Abragam, The Principles of Nuclear Magnetism, ch.9 (Oxford 13C DNP-CP SPECTRUM Univ. Press, London 1961) 1 MSEC 5. A.Abragam and M.Goldman, Rep. NA = 2000 Progr. Phys. 4J_, 395, 1978 DL = 0.2 SEC 6. J.Trommel, Thesis, Delft MT = 400 SEC Univ. of Technology, Delft 1978 7. B.N.Provotorov, Sov. Phys. 13 CDNP-FID SPECTRUM JETP. Jj4, 1126 (1962) NA = 220 8. R.A.Wind, F.E.Anthonio, M.J. DL =10 SEC Duijvestijn, J.Smidt, J.Trom- MT = 2200 SEC mel and G.M.C.de Vette, J. Magn. Res. 52., 424 (1983) 9. J.H.N.Loubser and J.A. van i 1 '—l—— Wyk, Rep.Progr.Phys. 41, -300 -200 -100 0 100 PPM (from TMS) 1201, 1978 lO.M.Nechstein, F.Devreux, R.L. Greene, T.C.Clarke and G.B. Fig.6.The 13C CP, DNP-CP and DNP-FID Street, Phys.Rev.Lett 44, spectra of undoped trans^(CH)x 356, 1980. ning can be applied to enhance the spectral resolution (8).Many appli- cations are possible,like the fast measurement of C relaxation times, 2D and MQT spectroscopy and the stu- dy of 13C atoms in the vicinity of the free electrons. Finally also the detection of other rare spins besi- des 13C may be facilitated by the use of DNP. ACKNOWLEDGEMENT The investigations were supported by a grant from the Project Office for Energy Research of the Nether- lands Energy Research Foundation ECN, within the framework of the Dutch National Coal Research Program.One of us (MD) was supported by the Nether- lands Foundation for Chemical Re- search (SON) with financial aid from the Netherlands Organization for the Advancement of Pure Research (ZWO). Vol. 5, No. 3A 117 SPIN PHYSICS IN DISORDERED SEMICONDUCTORS I. Solomon Ecole Polytechnique, 91128 Palaiseau, FRANCE. It has been recognized for a long II. EXPERIMENTAL SPIN-DEPENDENT EFFECTS time that spin statistics have an impor- tant effect on recombination in semicon- Any experimental situation which tends ductors (1). This effect provides a con- to destroy the correlation of the spins venient and very sensitive method of re- of the electron-hole pairs will result sonant spectroscopy for the study of the in an increase of the relaxation rate, nature of deep centers and their recom- observed as a decrease of the photocon- bination properties even at room tempe- ductivity as is shown in Fig.l. rature. I. A PUMPING OF TRIPLET STATES _J / \ The magnitude of the effect is not < / \ compatible with the model of a single z i / \ recombination center near the middle of SI G 7' /\ the gap (2). z B \^_^ i To explain a spin-dependent effect as O large as 1% at room temperature, it is o necessary to assume a recombination F=1.9 GHz process through trapped electron-holes pairs (3) which can be shown to be an t extremely efficient recombination me- c chanism (4). In this model an electron \' trap (above the Fermi level) and a hole "\ trap (below the Fermi level) are close o 1— 1- enough (within 10 to 15 A) so that di- X > • rect recombination between the two trap- I ped carriers can occur. ; nv r \ This recombination is strongly spin- o \ \ dependent : since after the electron- Q .5- hole recombination the total spin is ze- o ro, the recombination is allowed only o for an electron and hole in a singlet o \ o spin-state. The spectacular result is I that the spins of an electron-hole pair Q. n - 0 ....,., , , ,.. , -^. populated by light are strongly corre- u lated. The singlet states tend to disap- 500 1000 MAGNETIC FIELD (GAUSS) pear by recombination whereas the popu- lation of triplet states, which cannot recombine, increases. Thus, by simply Figure 1 Variation of the photoconducti- vity of an amorphous silicon film as a shining some light on a semiconductor, function of the applied magnetic field. it is possible to produce a "pumping" Top : Lock-in signal for a 12 Gauss (p to of all the electron-holes pairs in a p) modulation of the field. Bottom : The same curve integrated to show the quanti- triplet state, instead of the usual pro- tative spin-dependent variation of the portion 1/4, 3/4 of singlet and triplet photoconductivity. Curve A is the resonant effect and disap- states for randomly oriented spins. pears when the 1.9 GHz microwave field is not applied. 118 Bulletin of Magnetic Resonance A. Resonant Spin-Dependent the origin of curve C, in Fig.l, seen as Photoconductivity very low field spin-dependent photocon- ductivity. The magnitude of the effect By resonant "saturation" of one of is of the order of 10~3 and its range the spins of the pair, usually the trap- (10-30 gauss) is quite comparable to the ped electron resonance line (the trapped spin resonance linewidth. hole has generally a much larger line- width), we induce rapid transitions bet- III. CONCLUSION : A TOOL FOR THE ween the two states of the resonant spin STUDY OF DISORDERED SOLIDS and the correlation between the 2 spins of the pair is lost. This is shown as A condition for the formation of a line A in Fig.l, for a resonance fre- finite density of electron-hole pair is quency of 1.9 GHz. It is interesting to the existence of a large number of pos- remark that the magnitude of the effect sible levels in the gap which is a cha- (close to 10~3 in amorphous silicon) is racteristic of disordered solids (4). the same as for saturation at the more This probably explains why the recombi- usual 9.5 GHz resonance frequency. This nation in crystalline silicon is mostly independence of the resonance frequency due to disordered regions of the sample is a crucial test of the model of recom- like surfaces, grain boundaries or dis- bination described in paragraph I. locations. The spin resonance signal of the recombination centers, obtained by B. Non-Resonant Spin-Dependent spin-dependent spectroscopy, is very si- Photoconductivity milar to the signal obtained in amor- phous silicon which is an extreme case The application of a dc magnetic of disordered silicon. field, without the use of a resonant mi- crowave field, will also destroy the spins correlations and thus decrease the REFERENCES photoconductivity (Fig. 1, curve B). Be- cause the g-values of the electron and 1D. Lepine, Phys. Rev. B£, 436 (1972). the hole of a pair are slightly diffe- 2W. Sehockley and VJ.T. Read, Phys. rent, the two spins precess at a diffe- Rev. 87_, 835 (1952). rent rate around the applied dc field H, 3l. Solomon, J. of "Non-Cryst. Sol. 35_ and a triplet pair will be destroyed af- and 36^ 625 (1980). ter a time of the order of 4l. Solomon in Topics in Applied Phy- T = *Wk [(ge " gh)_VB HJ "1 sics, Volume 36, Springer-Verlag, Hei- where Jig is the Bohr magnetic moment. delberg (1979) Chapter 7. For a typical value of ge - g^ 0.003 in silicon, the spin-phase loss due to the magnetic field will be obtained for an applied dc field of the order of 200-300 gauss, as observed on fig. 1. C. Zero-Field Spin Mixing The strong correlation between the electron-hole spins can be expressed, in the language of "spin-temperature", as a very "cold" dipole-dipole energy. Now, for an applied field of the order of the resonance linewidth or less, the dipole- dipole system will be strongly coupled to the much "hotter" Zeeman energy. This also will result in a destruction of the triplet spin-states, seen again as a de- crease of the photoconductivity. This is Vol. 5, No. 3A 119 DIMER CREATION AND ANNIHILATION DYNAMICS IN HYDROGEN-ARGON GAS MIXTURES Claude Lemaire and Robin L. Armstrong Department of Physics, University of Toronto Toronto, Canada M5S 1A7 I. INTRODUCTION require that full account be taken of the existence of For many years, nuclear resonance collisions, bound spin relaxation time measure- states and inelastic ments made as a function of collisions. With the density, p, on gas phase exception of H2~He mixtures, molecular systems have been no complete analysis exists. used to determine the nature In the earlier NMR exper- of the two body inter- iments on H2~noble gas mix- molecular potentials between tures it was assumed imp- the constituents of such sys- licitly, that the density de- tems. Of particular interest pendence of Tx in the inter- are proton spin, longitudinal mediate density regime was relaxation time, Tx, linear. This was the as- measurements (1-3) on mixtures sumption, at least within the of molecular hydrogen dilute limits defined by the typical in noble gases. If one 5% experimental error possible considers the entire sequence in the measurement of T, at of hydrogen-noble gas mixtures that time. However, for "'more studied (He, Ne, Ar, Kr, Xe) accurate measurements of Tt one goes systematically from this need not be the case for binary mixtures that sustain those mixtures in which dimers no bound rotational or are present. Since the vibrational states, as is the process of dimer formation is case for H2-He mixtures, to a three body collision binary mixtures with many process, it is reasonable to rotational and vibrational expect some amount of non- levels, as for H2~Xe mixtures. linear behaviour in the den- The occurrence of these bound sity variations of In- states, or dimers, might be deed, optical pumping expected to manifest itself on electronic spin the NMR data. Indeed, an ex- relaxation experiments on Rb-noble gas amination of the data in the mixtures (4 low temperature region shows 5) have shown an "anomalous" density dependence that a systematic increase of the occurs in the quantity electronic spin relaxation time due to dimer (T1/p)lin, characteristic of the intermediate density re- formation. In this paper, we gime of the relaxation time, present evidence for a similar effect in the proton spin as one goes from H2-He to H2~ Xe mixtures. A proper an- relaxation time measured in a alysis of these data would 10% H2 in Ar mixture. The Tx data were taken at 160 K. 120 Bulletin of Magnetic Resonance II. EXPERIMENTAL TECHNIQUES Both the absolute temp- erature and its gradient were Measurements of Ta were controlled automatically to made using a pulsed NMR within 1/3 K. The temperature spectrometer operating at 19 was measured to within 1/2 K MHz. Data acquisition was with a calibrated copper- under the control of an on- constantan thermocouple. line Tektronix 4051 computer. Sample densities were obtained To assure a high degree of through virial coefficient reproducibility in the data, calculations using pressure many elements of the NMR measurements. All pressures system were provided with were measured to within 1/2% feedback networks. The output with a calibrated Bourdon cell level of the rf power (0-1000 psi). amplifier was sampled period- ically and maintained auto- III. RESULTS AND DISCUSSION matically to within 1/2% of its set value. The Varian Fig. 1 shows the experi- V7000 electromagnet system was mental values of Tx/p for a supplemented by an external 10% H. in Ar mixture at 160 K, NMR field regulator providing long term stability (40 Hz/ day). All local oscillators in the heterodyne rf receiver were phase-locked to the master crystal oscillator of a Fluke 6039A frequency synthesizer. Spurious echoes on the transverse NMR decay were minimized and good rf field homogeneity obtained by con- taining the gas sample in a quartz cell within the rf coil. Pressurized helium gas outside the cell provided the necessary mechanical support for the cell under pressure. This gas also assured a uni- form temperature in the region about the cell. Spurious 20 40 60 80 non-exponential longitudinal decays caused by rf pulse DENSITY (amagat) imperfections or instrumental non-linearities were greatly reduced by the use of a phase alternation inversion-recovery Fig. 1. Density dependence of pulse sequence (6). The Tx/p in a H2~Ar mixture. present Tx measurements are estimated to be accurate and measured as a function of precise to within 1/2%. density p. In a comparable H2-He mixture Tx/p is a con- stant independent of the den- sity. For the H2-Ar mixture Vol. 5, No. 3A 121 the deviation of the T,/p hydrogen molecule angular values from a constant is well momentum becomes comparable to outside of the experimental that of a binary collision, a error. The data indicate a saturation will occur and Tx/p maximum in Tx/p near 15 will decrease with a further amagats. We note that this is increase of density. The the same density for which, in details of the non-linear the infrared spectrum of H2, density dependence of Tx/p the collapse of the fine will depend on the strength of structure associated with the the anisotropic part of the presence of H2Ar dimers occurs intermolecular potential (7). Dimers do not form in between an H2Ar pair. H2-He mixtures. The behaviour With this description of of Ta/p in the H2~Ar mixture the collision process, it is a manifestation of the follows that the average presence of dimers; the angular momentum correlation enhancement of Tj/p can be time, Tj, of an H2 molecule in qualitatively understood as rotational state J will obey a follows. relation of the form At low densities only bi- nary collisions are important and they give rise to the familiar linear variation of Tx with density so that their where the term 1/Tj, due to contribution to Tx/p is the binary collisions, is independent of density. As proportional to the density the density increases, three and the term 1/Tj, due to the body collisions become presence of dimers, has the important. For example, a general" density dependence binary collision resulting in outlined above. the formation of a resonance For the spin-rotation state may be closely followed intramolecular nuclear spin by a collision with a third relaxation mechanism the molecule resulting in the relaxation time Tx in H2 is formation of an H2Ar dimer, related to the correlation which will persist at least time by the usual NMR until the next collision, = r expression sr Such three body encounters will rapidly increase with the will certainly density and * "« sr disrupt the linear variation density. More of with where w is proportional to specifically, the result of the dimers is to enhance the the spin-rotation coupling motional narrowing effect constant. A similar expres- already present with binary sion exists for the dipole- collisions and thereby to dipole nuclear spin relaxation mechanism. A detailed cal- lengthen Tl so that Tx/p will increase with the density. culation of the dimer induced When, at still higher den- density dependence of Tx/p for sities, the average lifetime the H2-Ar system will be of a dimer decreases to the published elsewhere, together point where its effect on the with an extensive set of new experimental data which 122 Bulletin of Magnetic Resonance illustrates the variation of REFERENCES Tr/p both as a function of temperature and density. Fig. (1) J.W. Riehl, C.J. Fisher, 1 shows the result of such a J.D. Baloga and J.L. calculation as applied to the Kinsey, J. Chem. Phys. present data at 160 K; the J58, 4571 (1973) . solid line is the best least- squares fit of the theoretical (2) J.W. Riehl, J.L. Kinsey, model to the data. The J.S Waugh and J.H. analysis provides an average Rugheimer, J. Chem. Phys. dimer annihilation cross ^9, 5276 (1968). section of -111 A2 and an equilibrium rate constant (3) K.R. Foster and J.H. k = 1.56 x 10 cm assoc- Rugheimer, J. Chem. Phys. iated with the chemical _56, 2632 (1972). equilibrium equation (4) C.C. Bouchiat, M.A. H., + Ar H2Ar Bouchiat and L.C.L. Pottier, Phys. Rev. 181, Also the binary collision 144 (1969). cross section is found to be 0.72 A , a result which is (5) C.C. Bouchiat and M.A. consistent with that obtained Bouchiat, Phys. Rev. A2, from other types of 1274 (1970). experiments (8,9). (6) D.E. Demco, P. Van Hecke and J.S. Waugh, J. Mag. IV. CONCLUSIONS Res. 16, 467 (1974). We have presented a pre- (7) A.R.W. McKellar and H.L. viously unreported non-linear Welsh, J. Chem. Phys. density dependence of the 5JJ;, 595 (1971). proton spin longitudinal relaxation time Tx in a 10% H2 (8) T.E. Raidy and F.R. in Ar mixture measured in the McCourt, Chem. Phys. intermediate density regime. Letters 38^ 300 (1976). This effect has been shown to be related to the formation of (9) R.L. Armstrong, K.E. H2Ar dimers. This type of Kisman and W. data is seen to give access to Kalechstein, Can. J. the three body collision Phys. 53i, 1 (1975). process that gives rise to dimer formation. Vol. 5, No. 3A 123 INFRARED SPECTROSCOPY OF MOLECULAR IONS AT THEIR DISSOCIATION LIMITS by Alan Carrington, Richard A. Kennedy and Timothy P. Softley (Dept. of Chemistry, University of Southampton, Southampton S09 5NH, England) We have found that molecular ions extracted by acceleration from an electron impact ion source possess sufficient internal energy that levels close to the dissociation limit are populated. Consequently photodissocxation can be produced by infrared radiation, and resonance spectra arising from variations in the photocross-section as a function of infrared frequency can be observed. In our experiments beams of ions, at potentials from 1 to 10 kv, interact with a CW infrared laser beam from a CO or CO laser. The photofragment ion is separated from the parent ion by means of an electrostatic analyser, and detected after amplification of the fragment ion current with an electron multiplier. By scanning the parent ion beam potential and aligning the laser beam to be collinear with the ion beam, frequency sweeping occurs through the Doppler effect. Resonance spectra arising from changes in the photofragment intensity may be detected by modulation of the ion beam potential, which is essentially equivalent to frequency modulation, or by laser chopping, and detection with a lock-in amplifier. We have observed the spectra of five different molecular ions. The first was the HD ion, studied by means of a sequential two photon method: + + + HD (v», N») ^ ^HD (V, N-) & > HD * The first transition is a resonant vibration-rotation transition, and it is detected by observing the increased photofragmentation to H and D ions arising from subsequent excitation to the first excited electronic state (denoted by the asterisk) which is repulsive. We have measured rotational components of the 18-16 and W-'\h vibrational band systems, with an accuracy of ± 0.001 cm~^. The results provide a stringent test of ab initio calculations, and show that the existing theory is less accurate as the rotational quantum number N increases. Our ultimate objective is to detect transitions involving the highest bound vibrational levels, predicted to be v=20 and 21. The spectroscopic resolution is very high, and proton hyperfine splitting is observed for all transitions. The remaining four ions have all been detected through predissociation following infrared absorption; for example, the HeH has been studied by detecting H ions arising from the process: HeIT HTI + (v"/ .i, N"»TH)\ hV >^ He„ TTH+ .(v' , , „,N'.) predissociation ^> TTHe +ITH+ The transitions detected are from bound levels (v", N") to rotationally- quasibound levels (v1, N') which lie above the dissociation limit but are metastable because of tunnelling through centrifugal barriers. Bulletin of Magnetic Resonance The experimental frequencies and line widths show that existing adiabatic theories are accurate to better than 1 cm"1. The CH ion has been studied through the predissociation process: + + + CH ^ * CH * • C + H Using a CW carbon dioxide laser operating in the range 878 to 1093 cm"1 we have observed almost 100 resonance lines of varying width and intensity; many of the lines exhibit doublet splittings. We are at present unable to assign the spectrum because of the lack of an appropriate theory to describe the energy levels close to the dissociation limits. The problem is important because of interest in the inverse predissociation as a mechanism for the formation of CH in interstellar gas clouds. The HeNe ion has also been studied through predissociation: „ „ + ,?y . s hv • „ + ,?-' . predissociation . „ •+ HeNe (<£ t ) >• HeNe (Ml •, ) - ^ Ne + u He ' 2 2 The spectrum can be assigned because of previous optical studies by Herzberg, and demonstrates that an electronic predissociation mechanism which does not involve the crossing of potential energy curves can occur. Finally we have observed a remarkable infrared predissociation spectrum of the H^ molecular ion: H+ !SL_* H+* predissociation^ ^^ N) + H+ Measurements between 878 cm"1 and 1093 cm"1 reveal the presence of more than 25,000 lines, with widths ranging from 1 to 100 MHz. Detailed study of the spectrum strongly suggests the existence of many metastable levels lying up to 2 eV above the lowest dissociation limit (v=0, N=0 for H ). Our results are closely related to reactive scattering, but can show the presence of Feshbach resonances several orders-of-magnitude narrower than those which scattering experiments can reveal. Vol. 5, No. */!» 125 RECENT DEVELOPMENTS IN THE THEORY OF NMR SHIFTS IN PARAMAGNETIC SYSTEMS R.M. Golding and R.O. Pascual The Univ. of New South Wales, PO Box 1, Kensington, 2033, Australia. I. INTRODUCTION 2 2 2 H - -ft V - 2e C-£.s V(r ) 2 ~e NMR spectroscopy applied to *e o e paramagnetic systems is a powerful tool in elucidating information about gsf).B + tf(hf) [1] such molecular systems. Any where V(r ) is the crystal field interpretation, however, from a set of e interaction and H(hf), the hyperfine NMR experimental results needs to be interaction. The form of V(r ) will viewed with care and, above all, with e depend on the crystal field an appreciation of the possible errors environment and we choose when the which may occur through the use of notential is of octahedral symmetry approximations. Aspects of these approximations will be explained in V(re) this paper. II. THEORY 2/5 The electron-nuclear interactions we shall consider in this paper are given by Eq. [4] of ref. (l) which represents the electron orbital angular momentum and the electron spin "*.H- [2] dipolar-nuclear spin angular momentum interactions of an electron associated dominantly with one nucleus coupling When the crystal field environment is with a nucleus with a non-zero of icosahedral symmetry magnetic moment. The NMR shift arising from this interaction is V(re) calculated along the lines outlined in ref. (2). Here we consider only n t-orbitals [3] where n • •£ + 1. The radial function is expressed in terms of the parameter 3. . In deriving numerical We shall illustrate the effect of a results from the analytical crystal field distortion from expressions we shall choose in this icosahedral symmetry by adding to [3] paper the values 3j = 2.275/a0 , £2 " a potential given by 2.2/a and 33 " 5/aQ for the fl case 13 but 33 - 8/aQ for the f case. [4J To illustrate the way these integrals may be used we examine the where (d3d.) is the usual NMB shifts of f systems in different rotation operator (3). crystal field environments. The interactions we need consider may be In examining the bonding effects we represented by the hamiltonian shall consider the paramagnetic ion 126 Bulletin of Magnetic Resonance surrounded by six ligands lying at a solution, however, is dependent on the distance of R along each of the three value of a6«) axes where each ligand is treated as a single atom with three p-orbitals Table 1. The NMR shift comparing the available for bonding. (in this paper exact with the multipolar expansion we choose R - 0.2nm.) results for (l) j = 5/2 only (2) j - 5/2 and 7/2 considered. III. RESULTS AND DISCUSSIONS R(nm) exact (ppm) multipolar (ppm) 0.1 (1) -537.45 -535-35 To simplify the presentation of the (2) -377.34 -355-11 results we shall consider only the j - 0.2 (1) -17.118 -17-118 5/2 level and the case when the (2) -11.899 -11.249 crystal field interaction is such that 0.3 (1) -2.2638 -2.2638 the E*' level is the ground state and (2) -1.5720 -1.4852 in addition when the energy separation JI 0.4 (1) -0.53799 -0.53799 of the • E and U' levels is much (2) -0.37347 -0.35280 greater than kT. With these 0.5 (1) -0.17641 -0.17641 approximations the NKR shift may be (2) -0.12244 -0.11566 written as 3[20 L 1280 /nkT M From Table 1 we note first that the AB multipolar expansion results are a very good approximation to the result 4irkT /21 from Eq. [5] even for an R-value as small as O.lnm. On the other hand the N(t) 160 F(t)Y 86400 S(t)Yc results in Table 1 illustrate that by considering only the j = 5/2 level 147 7t' will lead to considerable errors. Also the multipolar expansion terms N(t) 2G(t)Y», 5400 S(t)Y6 for the exact case are not a good M 7 [5] approximation unless R is very large. 735 7t The . temperature dependence also where N(t), F(t), G(t) and S(t) are reflects a difference. Eq. [5] may be functions of t(t-2£3R). Y4 and Y6 are expressed as the appropriate fourth order and sixth AB/B = -1.8253 - 4587.99/T [6] order linear combinations of spherical when R = 0.2nm. The exact solution harmonics which transform with for both j-levels cannot be expressed octahedral symmetry. as a simple function of T but the data Eq. [5] is applicable for all values may be fitted when R = 0.2nm to the of R. As R •> 0, L and M in Eq. [5] are expression L - 1/147 and M - 1/755 and when R is large approximates to AB/B = 5-5844 - 6107-63/T + 259808/T2 (/55)5 5 (777 L - (5/63 R )^ - (675/7&3 R )Yfi r i [7] M - (l/l66 5R5)Yi»+(675/ll2637R7)Y 3 6 The l/T term in |_7J is *he dominant A set of numerical results is given 2 in Table 1 comparing Eq. [5] with the term: the l/T term is significant. approximate expression of the We next illustrate the results for the NMR shift when bonding effects are multipolar terms with the complete 1 solution, namely, considering both the considered for an f ion in a crystal 5/2 and 7/2 j-levels and including field environment of octahedral crystal field and magnetic field symmetry. We express the appropriate mixing between the j-levels. (Note molecular orbitals as linear that in comparing the solution for j - combinations of the ligand p-orbitals: 5/2 only with the solution involving T2u symmetry a(2u)|f> + b(2u) |ir-type> both j-levels we have set the crystal field parameter at - 0 since &s does Tiu symmetry a(lu)|f > + b(lu)|Tr-type> not appear in 15] • The complete + c(lu) |o-type> Vol. 5, No. 3A 127 T = 300K, £f » 700cm \ a.+ = 4200cm"!, Table 3- The NMR shifts for j - 7/2 a6 - 0, a(2u) = 0.9931 and b(2u) - when the distortion fronI icosahedral -0.1222, a(lu) = 0.9822, b(lu) = symmetry is along the 3-fold axis for -0.1208 and c(lu) = -0.1611. The different R-values (l) along the results are given in Table 2. distortion axis and (2) at right angles. Table 2. The NMR shifts in ppm for R(nm) (1) (ppm) (2) ([ppm) the f-system for different values of R 0.1 480.• 5902 -249.• 9486 along the x axis. 0.2 57-.6074 -28..8160 R(nm) exact multipolar dipolar 0.3 17..0018 -8.• 5039 0.10 -498.6764 -496.3866 -11.0261 0.4 7-.1749 -3..5856 0.20 +31.1098 0-5 3..6727 -1,.8356 0.30 -8.4729 -8.5528 -8.6045 Energy 34.-3794 0.40 -1.4577 -1-4577 -1.0336 level 21..4058 0.50 -0.4295 -0.4295 -0.2779 scheme (cm~'L) 19..8245 -75..6098 Table 2 shows that the point-dipolar term is not a good approximation. (in Although the major contribution arises this case the dipolar term arises only from the l/T 2 term the other two terms from the ligand of the electronic wave are certainly significant. functions.) On the other hand all the multipolar terms yield a very close IV. CONCLUSIONS result when R is greater than 0«3nm. The temperature dependence of the The results in this paper are an NMR shift at the ligand may be extension of our earlier work (l, 2, expressed as: 4, 5) and illustrate further that AB/B - 153.18 - 43897/T + 2178991/T2 great care needs to be exercised in This expression differs markedly from interpreting NMR shifts of Eq. [7]. Here each term contributes paramagnetic systems. The significantly to the value of the NMR calculations show that the NMR shift shift. values are very dependent upon the Finally, we shall examine the effect crystal field environment of the of a distribution of the form given by paramagnetic ion and the inclusion of Eq. [4] from the results when an f^3_ bonding effects. In summary it is ion is in a crystal field environment clear that a single experimental of icosahedral symmetry when the result from an NMR nucleus in a distortion is along the three-fold paramagnetic molecule may yield a very axis. limited insight into its electronic The crystal field potential of and/or molecular structure. icosahedral symmetry is chosen to split the ^7/2 level by 100cm -1. The (l) R.M. Golding and L.C. Stubbs, results are given in Table 3- J.Magn.Reson. 33, 627 (1979)- Table 3 shows that the distortion (2) R.M. Golding and L.C. Stubbs, has a marked effect on the NMR shift. Proc.R.Soc.Lond.A.354_, 223 (1977) Above an R-value of O.lnm the angular (3) D.M. Brink and G.R. Satchler, and R dependence of AB/B follows very Angular Momentum, Clarendon Press closely the expected (3 cos2© - l)/R3 (Oxford) (1971) function. On the other hand the (4) R.M. Golding, R.O. Pascual and temperature dependence is not simply B.R. McGarvey, J.Magn.Reson. 46, proportional to l/T2 . For example, 30 (1982). the temperature dependence of the (5) R.M. Golding, R.O. Pascual and S. values of 57-6074 in Table 3 is Ann, J.Magn.Reson. 46, 406 (1982). AB/B - -4.7631 • 3671.45/T + 4515298/T2 128 Bulletin of Magnetic Resonance PROTON AND DEUTERON NMR IN AMORPHOUS SILICON D. J. Leopold, P. A. Fedders, and R. E. Norberg* Washington University, St. Louis, Missouri 63130 and J. B. Boyce and J. C. Knights Xerox Palo Alto Research Center, Palo Alto, California 94304 I. INTRODUCTION III. EXPERIMENTAL RESULTS AND ANALYSES Ti of protons and deuterons in a-Si A. Spin-Lattice Relaxation via Dilute prepared by plasma deposition usually Molecular H2 and D2 show power law minima at temperature below 100 Kin which the Ti(H) and Tj(D) are We have reported (2) DMR relaxations controlled by spin diffusion to dilute for Sample I. These include a 100 to 200 molecular H2 and D2 trapped in the samples. sec Ti associated with a DMR quadrupolar The a-Si provides a stable container for doublet signal arising from the TBD molecular hydrogen at temperatures up to fraction of the sample. There also is a 500K. The nuclear relaxations of the WBD (weakly bound deuterium) Ti minimum molecular 0-H2 and P-D2 reflect the below 1 sec which arises from spin dif- temperature variation of the phonon- fusion to dilute (M37O ppm) molecular D2- induced molecular electronic relaxation, Much of the D2 in Sample I presumably which varies systematically among host came from the D2 in the original gas materials. In addition, a well-defined mixture. In order to examine this ques- quadrupolar doublet, associated with an tion, two samples have been prepared by Si-D bond, characterizes the DMR signal plasma deposition from a gas mixture of from the tightly bound deuterium (TBD) 5%SiD,, and 95% argon (Samples IV and V). fraction of the heterogeneous a-Si samples. Our NMR measurements show 4 and 2 at.%H components arising from a significant II. EXPERIMENTAL PROCEDURE hydrogen isotopic impurity in the gas mixture. We have made NMR measurement between Tj(D) for the TBD doublet component 14.4 and 92.5 MHz on five a-Si samples plasma- turned out to be similar (at 30 MHz) for deposited (1) from 100%SiH-, 5%SiHu/D2, and both Samples IV and V. The TBD relaxa- 5%SiDi«/Ar gas mixtures. Substrate tem- tion data are represented by circles at peratures varied from 298 to 503 K and rf the top of Fig. 1. The curved solid line power levels ranged from 2 to 18 W onto indicates, for comparison, the doublet 20 cm cathode and anode surfaces. Table Tj(D) for Sample I. T-,(D) for the non- I summarizes some of the characteristics doublet component is shown as squares of these a-Si samples . The indicated proton (Sample V) and triangles (Sample IV). and deuteron concentrations have been There is a Tj(D) minimum visible in the determined by calibrated NMR spin counts. results for sample IV. Tj(H) measured at 92.5 MHz for Sample Table I. Characteristics of Five a-Si Samples . V are shown as solid dots in Fig. 1 Two SAMPLE 1 11 III IV V 30.0 MHz T}(H) measurements for Sample V at 5.4 and 298 K are shown as a diamonds. Gas 5% SiH4/D2 IOO%SiH 5%SiD4/Ar Mixture For further comparison the solid inverted triangles indicate 42.3 MHz Tj(H) results Substrate 25 25 230 25 230 Temp. (C) reported by Carlos and Taylor in their Harvard ill sample, which was prepared by Substrate Cathode Cathode Anode Cathode Anode sputtering and contained very little RF Power 18 2 2 15 15 molecular H (3). (W) 2 Figure 1 also shows the temperature 12.8 10.9 4.4 1.9 n(H) (%) 7 variation of the proton relaxation times — 13.4 10.3 n(D) (%) 24 10.5 Ta(H) observed for Samples II, III, and V. Vol. 5, No. 3A 129 Sample V has no molecular H2 detectable The fitting procedure yields via its relaxation effect on Tj(H) and Sample III has more H2 than does Sample II. Tla(D) = 13800 T1(D2) + 16 sec . (3) The Tj (H) data for Sample II and III have been analyzed, by removal of a non-H2- Ti(D2) is the relaxation time calculated related relaxation contribution similar for deuterons in isolated p-D2 molecules to the Harvard #1 data, to yield Tm(H), and B = 16 sec is a spin diffusion bottle- the proton relaxation component associated neck term. The Ti(D2) have been calcu- with the presence of molecular H2. lated (A) for 30 MHz, large electric field gradients of no symmetry, with parameter ~t 1 ! j 1" , r—r-| r- • r = 0, and a characteristic temperature T,(D)(30.0) 0C = 40 K. These parameters (5) have been o oTBD reported to describe the relaxation of A IV ° o dilute o-H in solid neon and argon and ——-—_ o V 2 D that of dilute o-H2 and p-D2in Sample I. A • - 100 ^ D In the rapid spin diffusion regime, A °^ A° and neglecting intermolecular EQQ inter- actions Tia(D)/Tj(D2) will reflect (2,6) the ratio of spin heat capacities of D o and P-D2 present: O J r T (D) 10 o la = 3n(D) V: o° n(D ) ;cond ) n ^\ "• v 2 A O X A • Here we have assumed the room tempera- A* ture para-D2 fraction of 1/3. 1 (H) A According to Eq. (3) the ratio in Eq. (4) is equal to 13,800 for Sample IV. . Harvard* • (423 A • A A Thus n(D) = 4600 n(D2) . Now the f aster- 11 a (92.5) o (46.0) relaxating deuteron signals were found ? (30.0) to correspond to 20% of the observed III A (91.8) V O (30.0) DMR in Samples IV and V, so (from Table • (92.5) 6 0. I) n(D)=2.7% and thus n(D2) = 5.9 x 10 " (5.9 ppm). For an a-Si site number 10 100 density of 5xl022cm~3 this corresponds 17 3 TOO to n(D2) =2.9x10 cm~ for Sample IV. This is a concentration similar to that Fig. 1. Ti (H) and Ti (D) in Six a-Si Samples . 17 3 reported for n(H2) (3.8x10 cm" ) in In a similar fashion the WBD fraction Sample 1, so the amounts of molecular deuteron Tj(D) results for Sample IV (Fig. H2 and D2 formed from 5%SIH- and 5%SiDi, 1) can be analyzed by reciprocal subtrac- are similar for the two samples made on tion of Ti(D) for the corresponding TBD room temperature cathode substrates at doublet (circles in Fig. 1) to yield the similar rf power levels. molecular-D2-related T (D): Consideration of the bottleneck term yields additional information. The (1) bottleneck deuteron relaxation rate is given by(2) where Tla is here the WBD relaxation arising from sources other than molecular (5) D2 (and taken in this case to be similar la to the TBD doublet Tj (D) . These Tm(D) results have been optimally fitted to The observed Tla(D) is 16 sec for the expression Sample IV and, taking b^=4 x10"8cm and 17 3 T' (D) = AT.CDJ + B (2) n(D2) = 2.9xl0 cm~ , Eq. (5) yields D =1.3x10~12cm2/sec. The corresponding la 1 ^ 130 Bulletin of Magnetic Resonance value determined for Sample 1 (assuming D(H,D) independent of n(H,D), in the clustered samples) was Dp = D^/26 = l.lx 10~12cm2/sec. By using Eq. (1) and the Ti« data deduced from Fig. 1 we can determine (6) the molecular correlation frequencies r2(T) for the dilute p-D2 and 0-H2 mole- cules in the various amorphous silicon samples. The angular-averaged, no- symmetry, r = 0 equation for the nuclear relaxation in 0-H2 or p-D2 is (4) i = I U3d"[F2(coo) + 4F2(2wo)] . (6) 2 5 Here F2 (u>) = r2/(u3 -r2) , a)d(H2) =3- 624 x 10 1 5 J sec" and wd(D2) = 1.588 xlO sec (7). F2 values can be calculated for each TJQ, data point. These T2 results are plotted in Fig. 2 for Samples I, III, and IV. For comparison, the curved lines indicate F2 results (4) for dilute o-H2 in solid neon and argon. 10 - The molecular relaxation of dilute o-H2 and p-D2 in non-magnetic solid hosts can be described via a phonon-Raman pro- 100 cess. It is anticipated (8,9) that T (K) (7) r = CE*(T*) Fig. 2. T2 for H2 and D2 in Three a-Si where E*(T*) is the tabulated Van Kranen- Samples and in Neon and Argon. donk function and T* is a reduced tem- perature T/Qc. The characteristic tem- B. The Quadrupolar Doublet: Tightly perature Qc has been found (5) to be Bound Deuterium 40 ± 2 K for o-H2 in solid neon and argon. A value 0C = 40 ±5 K has been found (6) to . Figure 3 shows DMR line shapes for describe proton and deuteron relaxation Sample V at 14, 23, and 33 K. The 66 kHz data in a-Si:H and a-Si:D,H samples. The doublet is similar to that reported in T2 points plotted in Fig. 2 have not in- Sample 1 and corresponds to the2.1%TBD volved any assumptions about the magnitude fraction. The narrow spike at the center of &c. The results however can be fitted corresponds to a small fraction which very well by Eq. (7) with 0C = 40 K. has line-widths which correspond closely There is an evident chemical trend in with the narrow central line in Sample L the sample-dependence of the molecular However in Sample V there is a third T2 data plotted in Fig. 2. The T2 curves component to the DMR, a broad central systematically shift downward (i.e., C, feature with little temperature depen- reduces) as one progresses toward host dence between 14 and 33 K and a resonance materials with larger polarizabilities. half width near 30 kHz (corresponding There is in addition an apparent distri- to a T2 ~ 5 ysec). bution among the F2 results for a-Si The quadrupolar splitting of 66 ±1.0 samples (Fig. 2). Those samples deposited kHz corresponds to a deuteron quadrupole more slowly at lower power levels show coupling constant larger coefficients C. v = = 88± 1.3 kHz (8) q Vol. 5, No. 3A 131 ij This work was supported in part by NSF DMR 80-10818 and 82-04166. REFERENCES 33K 1. R. A. Street, J. C. Knights, and D. K. Biegelsen, Phys. Rev. B 18_, 1880 (1978). 2. D. J. Leopold, J. B. Boyce, P. A. Fedders, and R. E. Norberg, Phys. Rev. B ^6, 6053 (1982). 3. W. E. Carlos, P. C. Taylor, S. Oguz, and W. Paul in Tetrahedrally Bonded Amorphous Semiconductors (Carefree, Arizona) Edited by R. A. Street, D. K. Biegelsen, and J. C. Knights (AIP, New York, 1981), p. 67. 4. P. A. Fedders, Phys. Rev. B 20, 2588 (1979) . 5. M. S. Conradi, K. Luszczynski, and 14 K R. E. Norberg, Phys. Rev. B ^0, 2594 (1979). 6. M. S. Conradi and R. E. Norberg, -200 kHz Phys. Rev. B 2A, 2285 (1981). 7. N. F. Ramsey, Molecular Beams, Fig. 3. FTQEDMRLine Shapes in Sample V. (Oxford University Press, London, 1956) p. 235. If the correlation between Vq and force 8. J. Van Kranendonk, Physica (Utrecht) constant shown (10) for DMR in diatomic 20, 871 (1954). molecules is valid in a-Si, then the 9. J. Van Kranendonk and M. B. Walker, above Vq corresponds to the Si-D infra Can. J. Phys. _46, 2441 (1968). red stretching mode absorption at 10. M. Mokarram and J. L. Ragle, J. Chem. 1460 ±10 cm-l Phys. 59, 2770 (1973). C. Impurity Relaxation Below 50 K the deuteron relaxation times Ti(D) for the tightly bound deuterium (TBD) in Samples IV and V (5%SiDi4/Ar) show a temperature variation similar to that for Sample I (Fig. 1). Similarly the proton relaxation times Ti(H) for Samples IV and V below 50 K are proportional to the corresponding Ti(D) results and similar to Ti(H) for the Carlos and Taylor results (Fig. 1) in a sputtered (I0W-H2) sample (3). However, above 50 K the Ti results for Samples IV and V are different from those for other a-Si samples we have studied. Both Ti(D) and Ti(H) decrease rapidly with increasing temperature. It is probable that this additional relaxa- tion arises from the presence of impurities . 132 Bulletin of Magnetic Resonance NMR AND LIBRATIONAL TUNNELING IN SOME AMMONIUM COMPOUNDS M. Punkkinen, E.E. Ylinen and L.P. Ingman Wihuri Physical Laboratory and Department of Physical Sciences, University of Turku, 20500 Turku 50, Finland I. INTRODUCTION gime (2irv T) » 1, where T is the corre- lation time of ammonium reorientations. Because protons are fermions, libra- By studying T as a function of V at a tional or rotational wave functions are constant temperature and by repeating the coupled to spin wave functions of sym- experiment at different temperatures one metric proton groups in solids. Ammoni- obtains V as a function of temperature. um rotations by -120 or 180 correspond This method has been used to determine to even permutations of the four pro- V for (NH,) PbCl, (8), (NH.) SnBr (9) tons, and therefore only such products ant for (NCKZnCl" (10). The splitting of the librational and spin wave func- of the 3T manifold was studied in NH.C10, tions are allowed which remain unchanged (11) and (NH,)2SnCl, (12). Some indica- under these symmetry operations. If the tion of a tunnel splitting was also ob- site symmetry of an NH.-ion is perfectly tained for ND.C1O4 and (ND^PtClg (13). tetrahedral, then the librational ground The field-cycling technique was employed state splits into so-called A, 3T and E to determine V in silane (14). Gener- levels with total spins of 2, 1 and 0, ally a tunnel frequency is observed to respectively (1). If the site symmetry decrease when temperature is raised. How- is lower, then also the three T levels ever, a reversed behavior is also possi- split. The distances between the levels ble within a limited temperature region in frequency units are called tunnel at low temperatures (9,10). frequencies, for example hV™. equals the energy difference between the T and A III. NONEXPONENTIAL RELAXATION levels in the case of tetrahedral symme- try. Often the proton spin-lattice relaxa- tion in ammonium compounds is markedly II. TUNNEL SPLITTING nonexponential. In single crystals the nonexponentiality probably arises from Although much precise information on the presence of many quasiconstants of librational tunneling has been obtained motion, for example the populations of by other spectroscopic methods, espe- the A, T and E tunnel levels and the to- cially neutron scattering (2), the pre- tal nuclear magnetization (15,16). Even sent paper deals only with NMR experi- the total magnetization itself may have ments on tunneling ammonium ions. two differently, relaxing components if If a tunnel, frequency V. is larger the A and T level populations cannot be than the width of the absorption line, described by a common Zeeman spin temper- then the observed width is narrower than ature. expected (1,3). Tunneling effects can We employed the pulse sequence 90 -t, also be studied in the rotating frame -90° AO-to-90° (17) to study the rate of for 2iTV roughly equal to yB , where lou , / , . Bis the rf magnetic field (4-6). When approach towards a common spin tempera- V is of the order of the proton reso- ture in (NH,)2SnBr6 (18). The interval t^ nance frequency V or larger, then also was adjusted to create a situation, where the spin-lattice relaxation time T is after the first two pulses the A and T affected (7,8). For example, if V = nV species magnetizations M and Hr,, respec- (n = 1 or 2), additional minima in T, tively, could not be described by a same may be observed in the slow-motion re- spin temperature. For short t~ the shape of the free induction signal at the end Vol. 5, No. 3A 133 of the pulse sequence deviates clearly Then the rate R is assumed equal to from the shape corresponding to thermal the corresponding direction-independent equilibrium. However, the thermal-equi- rate calculated using perturbation theo- librium shape is approached with in- ry (15). creasing t- at a rate 1/T , where T The A and T level magnetizations can is a characteristic time for spin dif- be written as fusion between the A and T species lev- els. [2] IV. A MODEL FOR SPIN DIFFUSION 3(ANT1-ANT_1). We present here a mathematical model By using the master equation we get the for analyzing the spin-diffusion experi- time dependence ment described above. The population of an individual spin-librational level is 1 = -(rA+3R)c~ AMA denoted by N , where s equals A, T or E and m is the z component of the total [3] spin. The populations of the three T = 3(rTA+R)c levels, NT,m, N^,,, and NT,,,m, are as- sumed equal (15,ID). The deviations of Here c = exp(hv ./2kT) and the relaxa- the populations from their thermal-equi- T tion rates are given in terms of the librium values are AN = N - N (eq). ± H rates R , W and U (n = 0, l, -2) of .. „ sm sm sm n n Next two Zeeman spin temperatures are Ref. 15 . assumed, one for the A species levels and the other for the T levels. (The rA = TS< VR-l+R2+R-2> + lR0 evolution of a spin temperature within the T levels need not necessarily be + iexp(-hVET/2kT)(U1+U_1+4U2+4U_2) faster than the spin diffusion between the A and T levels. In such a case the three-pulse sequence should still give the speed of the evolution of a spin temperature common for the entire spin rT = system, but the model to be described below would not be valid.) The equations [3] and [4] are valid only if the spin-isomer populations, for ex- The spin diffusion originates from ample I N. , are equal to their values three kinds of transitions A-2 TO «=» F , m Am' ...... T±lk A±l1, A±2k T+l1 «» T±lk AO* ana at thermal equilibrium. A-l, T+1-. «=* TO, AO.., which are induced The solution of the differential by the flip-flop term of the magnetic equations [3] depends on the initial dipolar interaction between the ammonium magnetizations M. . and 1 Bulletin of Magnetic Resonance T, is the Zeeman spin-lattice relaxation 9. L.P. Ingman, M. Punkkinen, E.E. Yli- time for the spin system after the de- nen and C. Dimitropoulos, Proc. XVII An- velopment of a common spin temperature. nual Conf. of Finnish Phys. Soc, Joen- When the free induction signals re- suu, Finland (1983). lated to M and M,^ are denoted by f«(t) 10. L.P. Ingman, M. Punkkinen and E.E. and f (t), respectively, we obtain for Ylinen, unpublished results. the induction signal following the 11. M. Punkkinen and J.P. Pyy, Physica three-pulse sequence (c =* 1) Fennica 10, 215.(1975). 12. J.J. Van der Klink and C. Dimitro- f(t) = MA(t2) fA(t) + fT(t) poulos, J. Phys. C: Solid State Phys. 15, 3381 (1982). (M0-(MAi+Hri-M0)exp(-t2/T1)) 13. Z.T. Lalowicz, M. Punkkinen and E.E. Ylinen, J. Phys. C: Solid State Phys. 12, 4051 (1979). xi(5f (t)+3f (t)) [6] A T 14. P. van Hecke and G. Janssens, Phys. Rev. B17, 2124 (1978). 15. M. Punkkinen, J. Magn. Resonance 19, 222 (1975). x(f (t)-f (t)). 16. A.J. Nijman, M. Sprik and N.J. Trap- A. i. peniers, Physica 98B, 247 (1980). Here Mfi = M (eq) + M^eq) and f (t) = 17. M. Goldman and L. Shen, Phys. Rev. q (5fA(tJ+3f Tt))/8 is theshape of the 144, 321 (1966). free induction signal at thermal equi- 18. M. Punkkinen, E.E. Ylinen and L.P. librium. Thus the second term in [6] Ingman, Phys. Rev. B26, 3943 (1982). describes the deviation of f(t) from 19. S. Emid, R.A. Wind, A.E. Zweers and f (t). Since for c =» 1 one has M_(eq) H.B. Brom, Physica 81B, 140 (1976). 3H^(eq)/5 the second term vanishes at thermal equilibrium. To be able to study T one has to create a situation where M. . and M_,. cannot be described by the same spin temperature. REFERENCES 1. K. Tomita, Phys. Rev. 89, 429 (1953). 2. See for example W. Press, Single- Particle Rotations in Molecular Crys- tals, in Springer Tracts in Modern Physics, Vol. 92, Ed. G. Hohler, Sprin- ger-Verlag, Heidelberg 1981. 3. Z.T. Lalowicz, C.A. McDowell and P. Raghunathan, J. Chem. Phys. 68, 852 (1978). 4. R.S. Hallsworth, D.W. Nicoll, J. Peternelj and M.M. Pintar, Phys. Rev. Lett. 39, 1493 (1977). 5. I. Svare, G. Thorkildsen and K. Ot- nes, J. Phys. C: Solid State Phys. 12, 2177 (1979). 6. K. Morimoto, J. Phys. Soc. Japan 50, 2404 (1981). 7. W. Guttler and J.U. von SchUtz, Chem. Phys. Lett. 20, 133 (1973). 8. M. Punkkinen, J.E. Tuohi and E.E. Ylinen, Chem. Phys. Lett. 36, 393(1975). Vol. 5, No. 3A 135 MAGNETIC RESONANCE STUDIES ON URANIUM COMPOUNDS loan Ursu, Voicu Lupei National Centre for Physics, IFTAR, 76900 Bucharest, Romania The main results recently obtained of interest for radiation detection; through magnetic resonance studies of (v) structure and properties of some some uranium compounds are reviewed, luminescent uranium centers that can with emphasis on their application in be used for detection of ultratrace nuclear power,nuclear physics and laser levels of uranium; (vi) determination physics. Thus, in nuclear power and of some important characteristics of nuclear physics magnetic resonances are the uranium nuclei, such as nuclear very helpful in solving problems such magnetic dipole and electric quadru- as: (i) measurement of isotopic abun- pole moments. In laser physics exam- dances of uranium by use of the inter- ples of problems addressed are: action of the nuclear spin of the odd (i) valence state of uranium ions in isotopes of uranium with other nuclei crystals; (ii) physical structure of (in case of NMR) or with the electron the uranium centers and its connec- spin (EPR); (ii)structure and dynamical tion with their electronic properties; properties of some uranium compounds (iii) crystal field studies; (iv)dis- used in the nuclear fuel cycle; tribution of the uranium ions among (iii) electronic structure of some possible centers and its connection hexacoordinated U complexes and its with crystal technology. connection with their physical struc- The use of magnetic resonances in ture; (iv) structure and properties solving these problems is illustrated of some uranium centers in systems by. a review of the results obtained with thermoluminescent properties in various laboratories throughout the world, including at the National Centre for Physics, Bucharest — in the study of UF by NMR and of various uranium centers in crystals by EPR. 136 Bulletin of Magnetic Resonance MOLECULAR DYNAMICS AND STRUCTURE OF LYOTROPIC LIQUID CRYSTALS OF NMR LINE SHAPE ANALYSIS G.Chidichimot A.Golemmet and J.W.Doane++ + Dipartimento di Chimica, Universita della I Calabria, 87030 Arcavacata di Rende, Italy -H-Liquid Crystal Institute, Kent State University, Kent Ohio 44242 The utility of deuterium NMR in the racteristic shape which depends upon the study of liquid crystals is no better value of the time averaged coupling con- illustrated than in its use in the deter- stant VQ=eQVzz/h and the motionally in- = mination of the structure of molecular duced asymmetry parameter ri (Vxx~Vzz)/ aggregates which occur in lyotropic Vzz. The principal components V£i are liquid crystals (1). In the past, the those of the time averaged electric study of the size and shape of these field gradient tensor. In the hexagonal aggregates has been reserved for X-rays and ribbon phase we calculate these quan- (2) of freeze-fracture electron micro- tities based upon the additional motional scopy (3) but we shall show in this pa- averaging that result when the lamellar per that deuterium NMR can in some ways phase is transformed into these aggrega- ! give a more precise measure of these tes. If we let V^'z be the z' component quantities. of the La phase then the new values of Lyotropic liquid crystals are known the quantities in the Ra or Ha can be to consist of a lattice of molecular calculated from the transformation equa- aggregates. The simplest and most common tions (6) . aggregate is that of the lamellar bi- 2 layer. In the La phase there is no order- i-| sin e> ing of the molecules within the bilayer L and a stack of bilayers forms a smectic v =v , , A liquid crystalline phase (see Fig.l). xx z z Another common structure is that of the •v =vL, , j Sin 0 Sin 0 -•£• elongated cylindrical aggregate. Most yy z z often (but not always as we shall show) where the time dependent polar angles 0» these aggregates form a hexagonal lat- 0 gives the orientation of z' in the x, tice, hence the nomenclature "H,^" phase. y,z principal axis frame of the RQ or Intermediate in concentration of tempe- Ha aggregates. rature between the La and Ha phase The result of the "Ha" phase is tri- there are proposed to be a number of vial in which case VG=-VQ72 and nc=0 possible different phases (4). One of where the superscripts C and L stand these is the ribbon phase (see Fig.l) for the cylindrical and lamellar aggre- which we shall label as the "Ra" phase gate respectively. In the RQ phase, we (5). visualize the aggregate to consist of a The deuterium NMR spectral patterns lamellar central region (L region) cap- for perdeuterated potassium palmitate ped by cylindrical end (C-region). If and 2fl20 for three phases are shown in we let W represent the probability the Fig.l. molecule is in the L region then when In our analysis of these spectra we expressed in the same frame: assume that the molecule and hence each deuterated site of the molecule has (2) ample time during the ^H-NMR experiment (^lO-^sec.) to sample all relevant with the result that orientations associated with the aggre- gate or its lattice site. In this case one has a spectral pattern with a cha- Vol. 5, No. 3A 137 Fig.l: Aggregate structure and associated spectral "patterns of a mixture of 63 wt% potassum palmitate, 7 wt% potassum laurate and 30 wt% water. ^H-NMR spectral patterns on the left are for perdeuterated potassum palmi- tate and those on the right for deuterated H2O. The two small outer peaks on each spectrum are due to a coexisting gel phase. v C —>vQ for j < W< 1 case of the perdeuterated lipid we use values of vk obtained from the spectrum (3a) in the H phase (Fig.lc) for each deu- for 0 ^W 138 Bulletin of Magnetic Resonance lindrical aggregate is rectangular ra- ther than hexagonal or square. In a rectangular lattice the orientation of a diffusing water molecule will expe- rience a two-fold axis of asymmetry thereby inducing an asymmetry parameter. The lipid component exhibits no asym- metry as the lipid molecule is confined to be in the cylindrical aggregate. Finally, we should like to comment that in these materials at other con- centrations we have observed spectral patterns which suggest dynamical pheno- mena. Unlike the spectral patterns shown in Fig.l, these patterns are not indicative of the fast motion regime. We currently believe these other pat- terns result from fluctuations in the aggregate structure on the time scale of the ^H-NMR experiment. ACKNOWLEDGEMENTS The work was supported in part by the Italian M.P.I, and NSF Solid State Chemistry grant DMR 82-04243 REFERENCES 1. G.Chidichimo, N.A.P.Vaz, Z.Yaniv, and J.W.Doane, Phys.Rev.Lett. 49, 1950 (1982). 2. J.Stamatoff, B.Feuer, H.J.Guggenheim, G.Tellez, and T.Yamane, Biophys.J. 38, 217 (1982). 3. R.R.Balmbara, 0.A.Buchnall, and J.S. Chunie, Mol.Cryst.Liq.Cryst., 11, 173 (1970). 4. V.Luzzatti, and A.Tardieu, Ann.Rev. Phys. Chem. 25, 79 (1979). 5. Y.Hendrikx, and J.Charvolin, J.Phys. (Paris) 42, 1427 (1981). 6. A.Abragam, The principles of Nuclear Magnetism, (Oxford University press) (1961). Vol. 5, No. 3/4 139 The Use of Mixed Liquid Crystals of Opposite Diamagnetic Anisotropies in NMR C. L. Khetrapal National Institutes of Health Bethesda, Maryland 20205, IKS.A. and Ratnan Research Institute Bangalore-560080, India I. INTRODUCTION meters is then used to determine the relevant order parameters. A compar- NMR spectra of molecules oriented ison of the so calculated order para- in mixtures of nematic liquid crystals meters with the experimentally deter- of positive and negative diamagnetic mined values produces satisfactory anisotropies lead to novel applica- agreement. The theory also explains tions of NMR spectroscopy of oriented the appearance of the two spectra at molecules (1,2). The direct dipolar the critical point. couplings (Dij's) between two inter- acting nuclei i and j vary gradually III. APPLICATIONS with relative concentrations of the solvents until at a critical concen- The spectra at the critical point tration and temperature, the values lead to the following applications. change abruptly to twice or half, with opposite sign depending upon the di- (a) Determination of chemical shift- rection of approach to the critical anisotropy (Ao): The difference point. A close examination in the between the centres of the two spectra vicinity of the critical point re- at the critical point in systems with veals the coexistence of two type of 3-fold or higher axes of symmetry spectra at a particular temperature yields the product of Ac with the such that the dipolar couplings in one order parameter (SC3) of the symmetry are twice with opposite sign to those axis. Evaluation of SC3 from the di- in the other. They arise from the polar couplings provides Aa without presence of two types of orientations using a reference compound or change corresponding to the preferential of experimental conditions. Results alignment of the liquid crystal optic on several systems such as acetonit- axes along and perpendicular to mag- rile and benzene have been obtained netic field. (2,6,7) and compared with those deriv- Theoretical interpretation of such ed from other methods. a behavior and applications of the observations are presented. (b) Separate determination of indirect spin-spin (J^x) an^ direct dipolar II. THEORETICAL INTERPRETATION (PAX) couplings between heteronuclei A and X: The spectra at the critical The results are well understood in point provide (JAX + 2D^x) and (JAX ~ terms of Landau theory (3-5). The DAx) where DAX is the heteronuclear free energy function of the system is dipolar coupling corresponding to the expanded in terms of powers of the orientation where the optic axis is two order parameters. Minimization aligned along the magnetic field direc of the free energy function with tion. This enables a separate evalu- respect to either of the order para- ation of JAX and DAX -~ information 140 Bulletin of Magnetic Resonance which otherwise cannot be obtained from the critical point, since the D^g values spectra of oriented molecules. It has are related by a factor of -2 and J been applied to systems like acetonit- remains the same, the 4 independent rile and phenyl selenyl chloride and parameters—namely one JAB> one ^AB bromide (2,8,9). two (SAB'S can be determined from the four independent spacings. (c) Determination of diamagnetic aniso- tropy (Ax) of liquid crystals„ At the IV. CONCLUSIONS critical point, the macroscopic dia- magnetic anisotropy of the system, NMR spectra of molecules oriented in which is a weighted average of the dia- mixed liquid crystals of opposite dia- magnetic anisotropies of individual com- magnetic anisotropies lead to several ponents, vanishes. From the known new applications. Determination of relative concentrations of the two chemical shift anisotropy using this liquid crystals, it is thus possible technique has the definite advantage to obtain the relative diamagnetic over other methods that the values can anisotropies. The values for various be obtained without the change of exper- systems thus derived are in good agree- imental conditions or the use of a ment with those determined by other reference compound eliminating uncer- methods (10). tainties generated by these factors. However, it must be emphasized that in (d) Precise determination of spectral this method, as in other methods, the parameters: In spin systems where the presence of "local effects" is not elim- number of independent line positions inated; hence the values derived even by nearly equals the number of spectral this technique contain contributions due parameters to be derived, it may turn to such effects. out that the parameters determined from a single experiment are quite imprecise. V. ACKNOWLEDGEMENT Such a situation was actually encount- ered in the AB2 system of 2,6-dichloro- I am grateful to Dr. E. D. Becker phenol (11). However, at the critical for helpful critical discussions. point where the two spectra coexist since the dipolar couplings are not in- VI. REFERENCES dependent and the indirect couplings are the same, the effective number of 1. C.L. Khetrapal and A.C. Kunwar, independent transitions from which the Mol.Cryst.Liq.Cryst. 72., 13(1981) spectral parameters have to be deter- 2. C.L. Khetrapal and A.C. Kunwar, mined increases resulting in better Chem.Phys.Lett. J52, 170(1981) precision. A value of J^g = 8.3 Hz has 3. K.P. Sinha, R. Subburam and C.L. been obtained for 2,6-dichloro phenol Khetrapal, Mol.Cryst.Liq.Cryst. from the spectra at the critical point (in the press) compared to 10.0 Hz and -7.0 Hz derived 4. K.P. Sinha, R. Subburam and C.L. from the spectra in the individual Khetrapal, Chem.Phys.Lett. £6, 472 solvents (11). The value determined (1983) from the spectrum in the isotropic 5. K.P. Sinha, R. Subburam, A.C. medium is 8.3 Hz. Kunwar and C.L. Khetrapal, Mol. Cryst.Liq.Cryst. (submitted) (e) Determination of parameters which 6. P. Diehl, J. Jokisaari and F. Moia, otherwise cannot be obtained from spec- J.Mag.Res. 49, 498(19821 tral line positions: The NMR spectrum 7. C.L. Khetrapal and A.C. Kunwar, of an oriented AB system does not pro- Israel J.Chem. (in the press). vide all three parameters namely J^B* 8. N. Suryaprakash, A.C. Kunwar and DAB and the chemical shift S^B from the C.L. Khetrapal, J.Mag.Res. (in the line positions which have only two in- press) dependent spacings. In the spectra at 9. N. Suryaprakash, A.C. Kunwar and Vol . 5, No. 3/1* C.L. Khetrapal, J.Organomet.Chem. (in the press) 10. P. Diehl and J. Jokisaari, Chem. PhysoLett. J57, 494(1982) 11. M.R. Lakshminaryana, A.C. Kunwar and C.L. Khetrapal, (to be pub- lished) Bulletin of Magnetic Resonance LATEST RESULTS IN INDOR SPECTROSCOPY V.J«Kowalewski Facultad de Ciencias Exactas, Universidad de Buenos Aires, Buenos Aires, 1428, Argentina. I. INTRODUCTION It was as long ago as in 1963 that monitored, this last one underwent chan- E.B.Baker and L.W.Burd (1) reported ges because the H2 field changes the po- that a spectrum of phosphorus from pulations of the energy levels involved, threemethylphosphite ( P(CH ) ) could due to saturation by H2. be obtained as a negative going set of Probably due to the development of peaks by detecting one of the proton some new, more exciting techniques, not lines with a R.F. field Hj of fixed fre- too much attention was afterwards given quency v] while sweeping over the region to INDOR spectroscopy except perhaps by of phosphorus resonances with another van Deursen (4) in some chemical pro- R.F. field H2. They called this experi- blems in which use was made of the abili^ ment INDOR. They did not advance any ty of INDOR of "digging out" lines from explanation; they only remarked that overlapping groups of signals due to similar results could also be obtained different compounds and by this author with other heteronuclear compounds. (5) in some problems in which the main It was suggested by R.Freeman and interest was to determine the correct W.A.Anderson (2) that this should be sign of some spin-spin coupling constant. a result of tickling. Since the proton Only in recent times a model, was able to re line on the top of which the recorder INDOR spectra (6) which was able to re- was set was multiply degenerate, that is, concile- the differences between Baker's it had several components all of them and Kaiser's INDOR spectra, showing the of the same frequency, any time the H2 continuous transition from one to another field perturbed a phosphorus transition as H2 was being increased. The model which was connected with one of the pro- could also give a hint as to the best va ton transitions of this particular line, lues of H^ and H2 to use to get the this was split and the recorder "fell "best" spectra. To show also the influen into the trough" thus produced, resting ce of factors like T^ and T2 and the re- only on the remaining lines. lative values of the magnetogyric ratios A simple analysis shows this to be and to account for the worse ratio of reasonable since in this way the typi- signal to noise ratio and bigger line- cal binomial pattern of such an AX spec width obtained with INDOR spectra, as trum could be reproduced. n compared with the standard ones. Shortly afterwards R.Kaiser (3) repor ted the results of a similar experiment II. THE MODEL OF INDOR SPECTRA perfomed on a homonuclear system (meta- dichlorobencene). His results differed The model recognizes the correctness from those of Baker and Burd since not of tickling as the main cause of INDOR only "down going" but als "up going" spectra of the Baker type, but emphasizes peaks were recorded. This was interpre- the importance of H2 on the redistribu- ted as being due to a "pumping action" tion of populations which happens for of the H2 field. Each time this field values of H2 much below saturation, in crossed over some transition connected fact its effect is predominnat for values with the one whose intensity was being of H2 smaller (measured in Hz.) than the linewidth. Vol.- 5, No. 3A It starts following R.Hoffman (7) as- lar case (3-bromothiophene-2-aldehyde) by suming that the observed intensity of a A.Cohen at at. (9) whith a kind of triple certain line in not only proportional to resonance experiment which could be cal- the square of the Ix matrix element but led "double tickling". also to the difference in populations of Since a tickling experiment gives rise the levels involved, that is: to some now lines, while INDOR on the con trary shows less lines than the original (N -N ) spectrum, looking thus easier to inter- obs x 1 l< (1) p q pret, it was thought of proffiting of Then the "master equation for popula- both techniques using both simultaneously. tions" (8) is used but a term is added The previously described INDOR model sug- which takes into account the transition gested a lineal independence of both tecli probabilities induced by the R.F. field niques. So it was decided to make a try. (or fields) and also assumes a Lorenzian An initial experiment was made on a lineshape: known AMX case, the vinyl group of vinyl acetate (10) which showed undoubtedly W(p,q) = Y2 H2 | There are problems of sign determina- tion of spin-spin coupling constants which cannot be solved, neither by tick- ling nor by INDOR techniques, like e.g. an AMX case in which J^ = 0. This parti cular problem was solved in one particu- Bulletin of Magnetic Resonance M.Czekalski, M.E. de Milou and V.J. REFERENCES Kowalewski, J. Mag, Res., ^4J_, 6j_, (1980), 44, 41, (1981). E.B.Baker, L.W.Burd and CV.Root, 7, R.A.Hoffman and S.Forsen, "Progress Rev. Sci. Inst., 34-, 243, (1963), in NMR Spectroscopy" (J.W.Emsley, J, R,Freeman and W.A.Anderson, J.Chem. Feeney and L.H.Sutcliffe, Eds.) Vol. Phys., 39, 806, (1963). 1, Pergamon Press, Oxford, (1966)). R,Kaiser, J. Chem. Phys., _39_, 2435, 8. C.P.Slichter, "Principles of Magne- (1963). tic Resonance". 2-nd Ed. Springer- F.W. van Deursen, Org, Mag. Res. 3^, Verlag, New York 1980 page. 141. 221, (1971). ~ 9. A.D.Cohen, R.Freeman, K.A. Me Lauchlan V.J,Kowalewski, D.G. de Kowalewski and D.H.Whiffen, Mol. Phys., _7, 45, and E.Ferra, J. Mol. Spectr., _20, (1963). 203, (1966), V.J.Kowalewski, J. Mol. 10. M.E. de Milou and V.J.Kowalewski, J. Spectr., _30_, 531, (1969), 3jL_, 256, Mag. Res., ^6_, 54, (1982). (1969); V.J.Kowalewski and R.Contre- 11. V.J.Kowalewski and P.E.Balonga, to be ras, J. Mag. Res., 8_, 101, (1972), published. 39, 291, (1980). Vol. 5, No. MAGNETIC RESONANCE STUDIES OF SPIN DYNAMICS IN ONE-DIMENSIONAL SYSTEMS M. Nechtschein, J.P. Boucher, F. Devreux, F. Genoud, and J.P. Travers ER CNRS "Dynamique de spin" associee au Departement de Recherche Fondamentale (section RM) du CEN-G 85 X, 38041 Grenoble Cedex, France I. INTRODUCTION TO THE METHOD (1) Ti The aim of this survey is to illus- where X i-s the reduced spin suscepti- trate use of Magnetic Resonance (MR) bility (X = X/ (gUg)2), «- and d are the as a specific tool for investigating scalar (isotropic) and dipolar part of magnetic and transport properties in the electron-nuclear coupling, respec- solids, more particularly in those tively ; f(w) is the motion spectrum, solids which exhibit one-dimensional defined as the following two spin (1D) properties. The basic idea is that correlation function : the characteristics of the spin motion - i.e. the "spin dynamics" -, as deter- f(w)=/~dt (2) mined by MR methods, reflect electron —°° interactions which are related to Thus, by measuring Ti as a function of magnetism and transport properties. the frequency, the motion spectrum For instance, exchange couplings can be described within two windows b_etween electron spins,$?x = !< J^» corresponding to co£ and 0)^, respective- S^S^t, make the a component of the spin ly. Typically this method enables us located at site A to be time dependent to explored energy spectrum up to (since §£x, S^] * 0). Moreover, a ^ 10K(ilue/k = 10 K for Ho = 7.5 Tesla) . "true motion", that is a displacement Still using nuclear spins as fixed of the electron spins can exist. This probes, in Dynamic Nuclear Polarization is the case for the spins which are (DNP) experiments the rate of the spin carried by conduction electrons in motion can be conclusively compared metals and semiconductors. This is al- to the Larmor frequencies (2,3). If so the case for the spins which are the motion is as fast as U)e - e.g. associated with band alternation 1011 rad/s -, energy can be transferred defects, or topological solitons, in from the electron to the nuclear Zeeman -ttfl.n-6-polyacetylene, (CH)X. reservoir. Then, pumping microwave The spin dynamics can be studied power at U)e results in a change of the through nuclear spins, which are used NMR signal amplitude (observing at as fixed probes undergoing local magne- (%). This is the Overhauser effect tic field fluctuations. Among the (0E). On the other hand, if the charac- components of these fluctuations, those teristic rate of the motion is less at the Larmor frequencies are efficient than Wflj (*v 107 rad/s), the electron- to make the nuclei to relax. More nuclear coupling corresponds to the precisely, the terms I+S? and I+ST of static limit. Upon DNP experiments, the electron-nuclear coupling give rise the so-called solid state effect (SSE) to nuclear flips which involve the is obtained. Namely, by pumping at spectrum of the motion at (JJJJ and (at 0)e ± w^j, positive, or negative, enhan- least in the high temperature limit) cement of the NMR signal is observed. ooe ± (JOJJ = coe, respectively ; where 0)^ Lastly, the spin dynamics can be and U)e are the nuclear and electron derived from the ESR lineshape by a Larmor frequencies, respectively. The detailed analysis of the motional resulting nuclear relaxation rate,'for narrowing processes. The motion spec- a powder sample, is given by (1) : trum is probed over the frequency Bulletin of Magnetic Resonance range included inside the ESR line and II. APPLICATIONS the informations are obtained in terms of four spin correlation functions. A. SPIN DIFFUSION IN HEISENBERG CHAINS The above considerations are quite general, i.e. whatever the shape of the The position of a given electron motion spectrum. The later is, of cour- spin is fixed, but its orientation is se, characteristic of the interactions, modulated by the exchange interactions denoted as A, which are responsible for with other spins. In the hydrodynamical the spin motion. However, its shape is limit (a) -> 0, k -> 0), the local spin crucially dependent on the dimnnisX.on.Oi- fluctuations obey a diffusion law with LLty of the motion. In the case of 3D a diffusion coefficient of the order of interactions the spectrum is flat as the exchange integral D// % J (8). The long as ti) « A. Thus, if one determines cutoff frequency is connected to the the motion spectrum by measuring Ti inter-chain exchange J', through a versus frequency, which is the more motiononal-narrowing-like mechanism, direct method, one is restricted to which is reduced by the one-dimensional small energy systems (-hA/k ^ 10 K). The character of the motion : 1 3 first study of this kind was reported ooc ^ J' (J'/J) ' (3,6). In contrast to by Myers and Narath in 1971 (4). static measurements (static susceptibi- On the other hand, in the case of lity, specific heat) which should be 1D diffusive motion the spectrum pre- performed down to very low temperature 1 2 sents a divergence as to" ' for to->O. (Tc /JJ'), the interest of spin It is expressed as dynamics methods is that they enable determination of very weak inter-chain 1 f(co) = (3) couplings (J1 < 0.1 K) from room tempe- '2D//W rature measurements (3,6,9-13). Basi- cally, measurements as a function of where D .. is the diffusion rate along temperature are replaced by an explora- the chains. The nuclear relaxation ra- tion as a function of frequency at te, from Eqs. (1) and (3), is now room temperature. frequency dependent, even for systems in which the characteristic energy is B. 1D TRIPLET-EXCITON SYSTEMS very large as compared to the Zeeman 3 energy (A >> «e), e.g. 10 K. In prac- tice, f(u>) is always truncated and Semi-conducting salts of TCNQ remains constant for frequencies less exhibit triplet excited states which than a given cutoff frequency 0) , which can jump from a site to the next along is characteristic of the interactions the TCNQ columns. This is a ID random which disturb the 1D diffusion, in walk motion which can be studied from Ti measurements versus frequency (14). particular the inter-chain couplings. 1 2 As concerns the ESR lineshape it was The U)" ' law has been observed, the noticed (5,6) that the peculiar spin dimensionality of the motion (15) and dynamics in 1D gives rise to typical the temperature dependence of the jumping frequency (16) have been stu- motional narrowed ESR lineshape, name- pe, name died in ($ As CH ) TCNQ . The fact -(Yt) v1 3/2 3 3 2 ly the Fourier transform of e~ ~ that two excitons cannot be on the same Such a typical shape was recognized site at the same time suggests that twelve years ago in the 1D magnetic their motion may be affected by hard- compound (CH3KNM11CI3 (TMMC) and, very sphere-like interactions, which should recently (7), it has been observed result in a faster divergence of the directly in the time domain in new spectral density (like O)~3'4). However, organic conductors which exhibit extre- the exchange interactions which occur mely narrow ESR line (a few mG). during exciton collisions restore the to"1'2 law for the spin correlation ^unctions (17). Vol. 5, No. C. 1D CONDUCTORS corresponds to a defect in the alterna- tion of the C-C bonds. In other words it The 1D diffusion law Ti1 <* oT1/2 has is a wall between two domains, which been observed in 1D metal-like salts of differ from each other by the phase in TCNQ, although the observing frequency the single/double bond alternation. In (typically 0% ^ 10 Vrad/sec) is very the ^tan^-polymer the two domains small compared to the characteristic (right, and left of the wall) are dege- frequency of conduction electrons, name- nerated. One, thus, imagine that the 11 ly EF/n ^ 10 * rad/sec (18-21). It can soliton, i.e. the spin, can move freely. be shown that, in the small coulombic On the contrary, in the eXi-polymer, repulsion lumit (U -»• 0), the spin dif- the two mesomer forms do not have the fusion rate Ds, which is determined same energy. Consequently, the spin from Ti, is also the charge carrier will be trapped at one end of the chain. diffusion rate D , which is involved In -ttani-(CH)X, the frequency de- in conductivity ? Dg = Dc (20,21). This pendence of the proton T1 has shown theoretical prediction has been confir- that the spin diffusion is very fast med experimentally by observing that (D/, > 1013 rad/s) and very anisotropic 5 Ds and Dc follow similar variations as (D/y/D^ 10 ) (27). These results are a function of both temperature and /yj_ irradiation induced defects (22,23). confirmed by the analysis of the ESR These results base Ti measurements line, provided that trapping effects versus frequency as a new method for of the solitons, in particular due to transport property studies in 1D con- oxygen induced defects, are taken into ductors. Let us mention two applica- account (29,30). tions of these method yielding results E. MAGNETIC SOLITONS IN which could not be obtained from ANTIFERROMAGNETIC CHAINS standard conductivity measurements. a/ Determination of the conductivity Finally, we turn to magnetic chains anisotropy in powder samples (21,24). at temperature low enough that 1D ma- b/ Selective determination of conducti- gnetic ordering can develop over large vity of TTF, and TCNQ chains in range. As shown by neutron inelastic TTF TCNQ (21) (using selective scattering measurements performed in deuteriation of one type of chains, TMMC,magnetic solitons can be created and measuring the proton Ti of the in planar antiferromagnetic chains with other one). a magnetic field applied perpendicular to the chain axis (31). They correspond D. DIFFUSIVE SPINS IN to mobile walls between antiferromagne- TRAWS-POLYACETYLENE, (CH)V tic domains with ir-dephasing of the spin orientation in each sublattice. The fianA- (CH)x is a spectacular Each time a soliton passes a given site example of system with highly one-di- it results in a 7r-flipping of the two mensional mobile spins. From dynamic sublattices, which gives rise to nuclear polarization experiments it magnetic fluctuations around k = TT and has been proved that the electron spins 0) = 0. The solitons are then efficient which are present in cJj>~, and in mechanisms for nuclear relaxation. It is noteworthy that the longer the tAan&-(CH)x (25,26) have completely different behaviors (27) : they are undisturbed antiferromagnetic domains fixed in the cxi-polymer (observation the larger the amplitude of the u = 0 of the SSE), while they are mobile in fluctuations. Consequently, and at its t/ianA~f orm (0E) . This result is first sight paradoxically, it turns quite in agreement with the "soliton" out that the efficiency of solitons picture which has been proposed to for relaxing nuclei in antiferromagnets describe the impair electrons in tfuxyU>- increases when their concentration vanishes (32). In highly pure crystals (CH)X (28). Such a "soliton" 148 Bulletin of Magnetic Resonance the solitons move coherently along the 17. J.P. Travers, J. de Phys. ^2_, chains (33). However, their motion 1103 (1981). becomes diffusive when a small amount 18. F. Devreux, Phys. Rev. B J[3, 4651 of (magnetic or non-magnetic) impuri- (1976). ties is introduced (34). 19. G. Soda, D. Jerome, M. Weger, J. Alizon, J. Gallice, R. Robert, REFERENCES J.M. Fabre and L. Giral, J. de Phys. _38, 931 (1977). 1. F. Devreux, J.P. Boucher and 20. F. Devreux, these, Grenoble (1979). M. Nechtschein, J. de Phys. 3_5, 21. F. Devreux and M. Nechtschein, 271 (1974). Lecture Notes in Physics, edited 2. J.P. Boucher and M. Nechtschein, by J. Ehlers et al. (Springer J. Phys. _31_, 783 (1970). Verlag, Berlin 1979), vol. 85^ 3. J.P. Boucher, F. Ferrieu and pp. 145-157. M. Nechtschein, Phys. Rev. B 9_, 22. F. Devreux, M. Nechtschein and 3871 (1974). G. Griiner, Phys. Rev. Lett. 45, 4. S.M. Myers and A. Narath, Phys. Rev. 53 (1980). Letters _27, 641 (1971). 23. F. Devreux, K. Holczer, 5. R.E. Dietz, F.R. Meritt, R. Dingle, M. Nechtschein and M. Minier, D. Hone, B.G. Silbernagel and J. Phys. (Paris) 44, 33 (1983). P.M. Richards, Phys. Rev. Letters 24. E. Ehrenfreund and M. Nechtschein, _26, 1186 (1971). Chemica Scripta J_7, 39 (1981). 6. M.J. Hennessy, CD. McElwee and 25. H. Shirakawa, T. Ito and S. Ikeda, P.M. Richards, Phys. Rev. B ]_, 930 Makromol. Chem. J_79, 1565 (1978). (1973) 26. I. Goldberg, H. Crowe, P. Newman, 7. J. Sigg, Th. Prisner, K.P. Dinse, A. Heeger and A.M. Diarmid, H. Brunner, D. Schweitzer and J. Chem. Phys. ^70, 1132 (1979). K.H. Hausser, to be published in 27. M. Nechtschein, F. Devreux, Phys. Rev. B. R. Greene, T. Clarke and G. Street, 8. F. Ferrieu, J. Phys. Letters 19, Phys. Rev. Lett. 44, 356 (1980). L-383 (1977). 28. W. Su, J. Schrieffer and A. Heeger, 9. F. Borsa and M. Mali, Phys. Rev. Phys. Rev. Lett. _4j2, 1698 (1979). B j), 2215 (1974). 29. K. Holczer, J.P. Boucher, 10.. M. Ahmed-Bakheit, Y. Barjhoux, F. Devreux and M. Nechtschein, F. Ferrieu, M. Nechtschein and Phys. Rev. B 23, 1051 (1981). J.P. Boucher, Sol. State Commun. 30. M. Nechtschein, F. Devreux, JJ5, 25 (1974). F. Genoud, M. Guglielmi and 11. J.P. Boucher, M. Ahmed-Bakheit, K. Holczer, Phys. Rev. B 2]_t M. Nechtschein, M. Villa, 61 (1983). G. Bonera and F. Borsa, Phys. Rev. 31. J.P. Boucher, L.P. Regnault, B JK3, 4098 (1976). J. Rossat-Mignod, J.P. Renard, 12. Cl. Jeandey, J.P. Boucher, J. Bouillot and W.G. Stirling, F. Ferrieu and M. Nechtschein, Sol. State Commun. _33, 171 (1980). Sol. State Commun. 23, 673 (1977). 32. J.P. Boucher and J.P. Renard, 13. Cl. Jeandey and M. Nechtschein, Phys. Rev. Lett. 45_, 486 (1980). J.M.M.M. J_5, 1053 (1980). 33. J.P. Boucher, L.P. Regnault, 14. F. Devreux and M. Nechtschein, J. Rossat-Mignod, J.P. Renard, Sol. State Commun. J[6, 275 (1975). J. Bouillot and W.G. Stirling, 15. J. Avalos, F. Devreux, M. Guglielmi J. Appl. Phys. .52, 1956 (1981). and M. Nechtschein, Mol. Phys. 36, 34. J.P. Boucher, H. Benner, 669 (1978). F. Devreux, L.P. Regnault, 16. J.P. Travers, M. Guglielmi and J. Rossat-Mignod, C. Dupas, M. Nechtschein, J. de Phys. 43, J.P. Renard, J. Bouillot and 663 (1982). W.G. Stirling, Phys. Rev. Lett. 48, 431 (1982). Vol. 5, No. 3/k NMR STUDIES OF BIOLOGICAL MEMBRANES Joachim Seelig and Francois Borle Biocenter of the University of Basel, Klingelbergstr. 70 CH-4056 BASEL, Switzerland I. INTRODUCTION II. Binding of metal ions Nuclear magnetic resonance methods, in We have studied the interaction of particular H- and P-NMR, have mono-, di-, and trivalent metal ions proven to be powerful tools to study with bilayers of saturated and the structural and dynamic properties unsaturated phosphatidylcholines by of membranes. The bulk of previous means of deuterium magnetic resonance studies has been directed towards (7). Using selectively deuterated elucidating the hydrophobic membrane lipids the measurements of the interior. However, from a biological residual deuterium quadrupole point of view the specific recognition splitting provided a sensitive handle of phospholipid polar groups by to monitor directly the binding of membrane proteins is most intriguing ions, including the weak binding of and it is in this area of head group Na . From a systematic comparison of structure and head group interaction various ions the following conclusions where NMR methods could make important could be derived. (1) Addition of contributions to the understanding of metal ions led to a structural change lipid function. For pure_ lipid model at the level of the polar groups. The membranes comprehensive H- and P- glycerol backbone or the beginning of NMR studies are now available for four the fatty acyl chains were not different phospholipid headgroups, affected. (2) The strength of namely phosphatidyl-choline (1,2), - interaction increased with the charge ethanolamine (3), -glycerol (4,5), and of the _ metal, ion in the order -serine (6). In addition, the average Na+ Ca La . (3) The titration orientations of the choline and curves of phosphatidylcholine bilayers ethanolamine dipole were determined by with Ca amd La could be described means of neutron diffraction. Taken in terms of a Langmuir adsorption together these results provide a isotherm with an interaction rather detailed picture of the potential, and apparent binding orientation of the polar groups, their constants were derived. internal flexibility, and their rate of reorientation. III. Lipid solvation of cytochrome c oxidase Since the NMR and neutron diffraction data were obtained with pure lipid The interaction of cytochrome c model membranes this begs the question oxidase with the polar groups oT of whether similar structural and unsaturated phosphatidylcholine dynamic information is available for bilayers was, investigated by H-, intact biological membranes where the N-, and P-NMR (8). Cytochrome £ head groups are exposed to a variety oxidase was reconstituted into of membrane proteins as well as to bilayers composed of a single metal ions. We have therefore synthetic lipid, i.e. l-palmitoyl-2- investigated lipid head group oleoyl-sn-glycero-3-phosphochol ine interaction under a variety of (POPC). Due to its low gel-to-liquid different experimental conditions. crystal phase transition temperature (-5° C) this lipid supports enzyme function at low temperatures while the NMR spectra retain the characteristics 150 Bulletin of Magnetic Resonance of a fluid lipid bilayer. POPC was experiments demonstrate that it is selectively deuterated at the two possible to identify the methylene segments of the choline phosphoglycerol head group segments in moiety and the interaction of the intact E. coli cell membranes and that lipid polar group with cytochrome c the head group conformation is similar oxidase was investigated for four7 in intact membranes and model different segments of the membranes. The rate of head group phosphocholine moiety, namely the motion is drastically reduced compared quaternary ammonium group, the two to the free glycerol in solution. methylene segments, and the phosphate However, the data provide no evidence group, yielding a rather detailed for a strong polar interaction of picture for the movement of a phosphatidylglycerol with the membrane phospholipid head group in a protein proteins. Moreover, even though containing membrane. For all segments phosphatidylglycerol carries a net investigated the segmental negative charge addition of ions seems fluctuations in the reconstituted to induce much less of a membrane resembled closely those conformational change than is observed observed in the pure lipid bilayer under equivalent conditions for the even when a large percentage of the phosphocholine head group. lipid molecules was in direct contact with the protein surface. The rate of References segmental fluctuations was determined by measuring spin lattice (T ) 1. Gaily, H.U., Niederberger, W., and relaxation times. Taken together, the Seelig, J. (1975), Biochemistry H_, anisotropy parameters as well as the 3647. ~ T, relaxation times provide no evidence for any strong polar 2. Seelig, J., Gaily, H., and interaction between the phosphocholine Wohlgemuth, R. (1977), Biochim. group and cytochrome c oxidase, neither in terms of a coHformational Biophys. Acta 46J7, 109. change of the head group nor in terms of a significant immobilization of 3. Seelig, J., and Gaily, H. (1976) individual segments. Biochemistry 15, 5199. 4. Wohlgemuth, R., Waespe-Sarcevic, IV. Phosphoglycerol head groups in E. N., and Seelig, J. (1980) Biochemistry coli membranes ]9_, 3315. Glycerol selectively deuterated at 5. Gaily, H.U., Pluschke, G., Overath, various positions was synthesized and P. and Seelig, J. (1981) Biochemistry supplied to the growth medium of 20, 1826. Escherichia coli strain T 131 GP, which is defective in endogenous 6. Browning, J.L., and Seelig, J. glycerol synthesis as well as glycerol (1980) Biochemistry ^9, 1262. degradation and lacks the ability to synthesize cardiolipin (5,9). The 7. Akutsu, H. and Seelig, J. (1981) procedure enables the stereospecific Biochemistry 20^, 7366. labeling of the membrane phospholipids ( 80 % phosphatidylethanolamine, 20 % 8. Tamm, L.K., and Seelig, J. (1983) phosphatidylglycerol). Deuterium Biochemistry, 2j2, 1474. magnetic resonance spectra were obtained for cell membranes and lipid 9. Borle, F. and Seelig, J., dispersions either from total lipid unpublished results (1983) extracts or from purified Biochemistry submitted. phosphatidylglycerol or phosphatidylethanolamine. These Vol. 5, No. 3/4 151 NMR STUDY OF PROTEIN SOLUTION STRUCTURE, DYNAMIC AND CONFORMATIONAL TRANSITIONS V.F. Bystrov Shemyakin Institute of Bioorganic Chemistry, Moscow 117988, USSR I, INTRODUCTION II. APAMIN Polypeptide neurotoxins isolated Apamin, an active principle of the from venoms of different species captu- Apis mellifera honey-bee venom, is an re attention not only because they octadecapeptide with two disulfide posses highly specific biological acti- bonds (1). The overall conformational vity and are useful as essential tools stability of the apamin molecule direct- in neurobiological research, but also ly follows from CD spectra study (2) because they are convenient models for which demonstrate that the structure correlation of protein biological func- is highly abundant with right-handed tion with chemical and spatial struc- a-helical component and persistent ture of the molecules. Dynamic molecu- against pH change of aqueous solutiom lar conformation represents a crucial in wide range, presence of organic sol- factor in functioning of physiologi- vents and denaturating agents, and even cally active molecules. Even minor con- chemical modifications. Proton and C-13 formational transitions could play an NMR spectra also indicate the relatively important role in their biological me- rigid backbone folding of apamin and chanism of action. Thus, it is vitaly were employed as tools for three-dimen- significant to evaluate not only the sional structure determination (3-6)• binding site in, for instance, the pro- Signals in 300 and 500 MHz proton, tein ligant - receptor interaction, but and 75 MHz C-13 NMR spectra of apamin also to present data on conformational have been identified by the two levels changes, if any, that could occured in of assignment in the 1-D spectroscopy. the course of binding. On the first level the proton signals This note is a brief account of the are interconnected by homonuclear proton results obtained in the Shemyakin In- spin decoupling and assigned to a parti- stitute of Bioorganic Chemistry on cular spin multiplet system according to structure of selected venom polypeptide the specific NMR types of amino acid re- neurotoxins. By combined use of spec- sidues (3, 7). The second level implies troscopic techniques (NMR, ESR, CD, assignment of the observed spin system laser Raman, fluorescence) and selective to a specific position of the amino chemical modification of native molecu- acid residue in the apamin primary struc- les, the solution spatial structure and ture by heteronuclear C-13{H-l\ selective interaction of neurotoxins are revealed. decoupling of carbonyl signals (4, 8). Honey-bee apamin, scorpion insectotoxin In construction of the apamin spatial I-5A and cobra "short" and "long" neu- structure use were made of backbone rotoxins possess stable molecular con- H-NC -H and side chain H-CctC3-H vicinal formation as gross of backbone folding coupling constants (9) and deuterium ex- is concerned, although side chain ave- change rates of NH peptide hydrogens raged orientation and their mutual in- (3-6). The originaly proposed conforma- teraction could vary under different tion of apamin (5,6) was afterwards conditions of environment. slightly corrected (10) taking into ac- count recent reassignment of the Gln-16 152 Bulletin of Magnetic Resonance and Gln-17 resonances (11). It is com- close to one another owing to folding posed of a-helical unit (residues 6-16) of peptide backbone. and g-turn (residues 2-5) supported The conformational analysis of insec- by two disulfide bonds 1-11 and 3-15. totoxin I-5A proceeds in three steps - The laser Raman spectra demonstrate configuration of X-Pro amide bonds, similarity in torsional angles of the secondary structure, and three-dimen- both disulfide bridges (12). The de- sional structure. All three X-Pro bonds rived solution conformation of apamin were proved to be in the trans configu- better explains the spectroscopic re- ration by NOE connectivities of the sults (2-6,10-12) than structures pro- H(a,-i) and H (§,i.+l) protons. The se- posed earlier on the basis of confor- condary structure evaluation is based mational energy calculations using the on the vicinal coupling constant values, atomic (13) and residual presentations NH deuterium exchange rates and NOE (14) as well as secondary structure qualitative distance estimation for prediction (15,16). It could be consi- principal components of the. regular dered as similar to the conformation protein conformation (10,19). It was adopted on a receptor because of its revealed (10) that insectotoxin I-5A persistence against media conditions contains the a-helical part 11-19 and chemical modification as well as started with the g-turn 9-12 and the the fact that synthetic apamin posses- antiparallel g-structure 23-34 with ses full biological activity and the g-turn consisting of the 27-30 residues. same CD and NMR spectra (17) which is The work now in progress to combine considered (15) as evidence that the all NMR data by use of distance geo- information for the correct folding of metry algorithm (20) for building up the peptide chain is contained in the the complete three-dimensional struc- chain and not in an apamin precursor. ture of the molecule and evaluation However the overall rigid spatial the disulfide bond locations. The pre- structure is not the only feature that liminary results (10) obtained in pseu- is important for biological action. The doatom approximation reveal general chemical structure and presumably con- backbone folding of the molecule which formational flexibility of arginine could be compared with the X-ray crys- side chain is also crucial as follows tal structure of the "long" type scor- from a dramatic loss of neurotoxic ac- pion toxin, v-3 (65 residues) from Cent- tivity when both Arg-13 and Arg-14 are ruroides soulpturatus Ewing (21). In substituted either by lysine or by or- spite of absence of any homology in nithine (2) residues. amino acid sequence and different bio- logical action, the spatial structures III. INSECTOTOXIN I-5A of these scorpion toxins contain many closely related facets. Both have a-he- The solution spatial structure of lical and antiparallel g-structural insectotoxin I-5A (35 amino acid resi- fragments with nearly the same number of dues four disulfide bonds) isolated amino acid residues.Moreover the frag- from Caucasian scorpion Buthus eupeus ments are similarily packed one to ano- (18,19) is evaluated by extensive use ther in space. However toxin v-3 has of 2-D NMR spectroscopy. By scalar coup- additional 30 residues located in the N- ling correlated spectra in COSY and and C-terminal parts of the molecule. SECSY arrangements and especially by It is assumed (21) that exactly these -dipolar correlated NOE spectra practi- parts of "long" toxins are responsible cally every signal was assigned to par- for biological activity. Thus, it is ticular amino acid residue in the pri- likely that the structural similarity of "short" and "long" scorpion toxins mary structure (10.19). In addition to at least not directly connected with NOE for protons located in neighbouring their mechanism of action. Presumably residues more than 100 NOE interactions these types of scorpion toxins posses were observed for protons of unneigh- the same predecessor but are on diffe- bouring amino acid residues, that while rent stages of evolution. remote in the primary structure become Vol. 5, No. 3A 153 IV. SNAKE NEUROTOXINS spatial structure doesn"t touched, as has been shown here by NMR and also More advanced is the state of confirmed by laser Raman spectroscopy affairs in structured-function relation- (28), which demonstrates that g-struc- ship for snake venom neurotoxins beard- ture content doesn't change with pH va- ing curare-like activity (22), It is riation and crystallization. due mostly to availability in solubi- In comparison with "short" type of lized form of a target of the neuroto- snake neurotoxins the "long" neurotoxin xin action - nicotinic acetylcholine molecules have larger fractions predis- receptor (AChR) from the postsynaptic posed to conformational transitions membrane in the neuromuscular junction. when environmental conditions are Moreover there is a very extended ho- changed. This differential property molog set of snake neurotoxins, among might be important for binding of these them there are two major types - two neurotoxin types with their target - "short" neurotoxins with 60-62 amino nicotinic AChR in postsynaptic membrane. acid residues and four disulfide bonds, and "long" type with 71^74 residues V. BINDING OF SNAKE NEUROTOXINS WITH and five disulfide bridges. ACETYLCHOLINE RECEPTOR Extensive NMR study (see reviews 3, 6, 23—25 and references therein) demon- The availability of series of neuro- strates that the backbone folding of toxin derivatives with spin (SL) or the "short'1 and "long'1 neurotoxins in fluorescence labels in known positions solution is very similar to correspon- provides the means for outlining the dingly revealed by X-ray crystal struct topography of a neurotoxin binding site ture analysis (26,27). The general fea- (23,24,29). The selectively labeled de- tures of the folding are preserved in rivatives specifically bind to the so- wide range of pH and temperature, at lubilized AChR isolated from Torpedo least for terrestrial snake neuroto- marmovata electric organ with dissocia- xins. tion constants ranging from 3 to 80 nM Comparison of the neurotoxin spatial and the 2:1 stoichiometry. The two neu- organization shows that they posses a rotoxin binding sites were found to be common core structure constiting of at independent and indiscernible by disso- least three antiparallel g-strands. ciation constants and labels microenvi- Conformational stability of the struc- ronment but not identical in that the ture follows from 2-D NMR detection of nontoxic hexa(trifluoroacetyl)-neuro- interstrand proton NOE at different pH toxin II N.n.ox-uma competes for only of aqueous solution (24). Averaged po- one AChR binding site (29). sition of side chain groups could be The configuration of neurotoxin con- subjected to a reasonable degree of tact area in complex with AChR is esti- movement. In the '"short" neurotoxin II mated by correlation times and solvent of N.n.oxiana reorientation of the exposure of nitroxyl labels in a-Leu-1, His-32 imidazole ring is observed under Glu-2, Lys-15, Lys-26, Lys-27, His-32, its protonation condition. As "long" Lys-45 and Lys-47 mono-SL "short" neu- neurotoxins are concerned, two major rotoxin II N.n.ox'tana, His-71 mono-SL changes are revealed. First - the struc- "long" neurotoxin I N.n.oxiana, Lys-27 tural transition in the upper loop, mono-SL and Lys-15/Lys-27, Lys-27/Lys-39, initiated by protonation of the His-22 Lys-27/Lys-53, Lys-27/Lys-75, Cys-30/ imidazole ring in the N.n.s-iajnensis Cys-34 di-SL "long" toxin 3 N.n.si-amensis toxin 3, and second - in the C-terminal derivatives. The ESR data supported by fragment, connected with His-71 proto- fluorescence study (23,29,30) provides nation in the N.n.oxiana neurotoxin I. direct evidences on extended surface From the spatial model it could be rea- and on multipoint topography of the neu- lized that relatively large portions of rotoxin - AChR contact site. Photoaffi- the "long" neurotoxin molecule are nity cross-linking (23,31) indicates affected, but nevertheless the core of that the neurotoxin molecules when bound Bulletin of Magnetic Resonance to AChR are in direct contact with se- Neurotoxins as Tools in Neurochem. veral subunits of the receptor, not only March 22-24,1983,Berlin(West) (Yu. only with a-subunits whose function Ovchinnikov, F.Hucho,eds) W. de is to bind the natural neurotransmit- Gruyter,Berlin,1983. ter - acetylcholine. Thus the revealed 11. D.Wemmer, N.Kallenbach,jt/z Internat. multipoint topography of the binding Conf. on Magn.Res. in Biological might serve for locking the receptor Systems Abstracts,August 20-Septem- quaternery structure with normally ber 3,1982,Stanford,P187. closed channel and therefore prevent 12. A.Nurkhametov, E.Elyakova, E.Efre- the large structural changes, which mov, A.Miroshnikov, Bioorg. Khim J_, believed to be necessary for opening 16(1981). the channel and induction of nerve im- 13. E.Popov, VM&lnxkovbioorg.Khim. 5_, pulse transmission. There are some in- 828,1011,1471(1979) ;£,21(1980). dications that in the process of bind- 14. B.Busetta.FE'BS' Lett. 112,138(1980) . ing the "long" neurotoxin molecule is 15. R.Hider.U.Ragnarsson^EBS1 Lett.Ill, more subjected to a conformational 189(1980). transition for better fitness to the 16. R.Hider,U.Ragnarsson,BioeHm.B-£o- receptor surface. This might be respon- phys.Acta, 667,197(1981). sible for lower rate of association and 17. A.Nuriddinov, V.Okhanov, V.Tsetlin, dissociation of "long" neurotoxins in V.IvanoVsBioorg.KHm.1,5(1981) . comparison with "short" toxins, and 18. E.Grishin, T.Volkova, L.Soldatova, lend the neurotoxin receptor complex Bioorg. Khim. §_, 155(1982). more degree of quasiirreversibility, 19. A.Arseniev, V.Kondakov, V.Maiorov, than lock-and-key fit. T.Volkova, E.Grishin, V.Bystrov, Yu.Ovchinnikov,Bioorg.Khim. 9,No.6 (1983). REFERENCES 20. G.Cvippen,Distance Geometry and Re Conformational CalculationsJ) search 1. E.Habermann,Sconce ,177,314(1972) . Studies Press,Chichester,1981. 2. A.Miroshnikov, E.Elyakova, A.Kude- 21. J.Fontecilla-Camps, R.Almassy, lin, L.Senya.vina,Bioorg.Khim.!t> S.Ealick, F.Suddath, D.Watt, R.Feld- 1022(1978). mann, C&ugg,Trends Biochem.Sci. 6, 3. V.Bystrov, A.Arseniev, Yu.Gavri- 291(1981). lov,J.Magn.Res.3Q, 151 (1978). 22. E.Karlsson, in Snake Venoms (C.-Y. 4. V.Okhanov, V.Afanasiev, A.Gurevich, Lee, ed.) Springer Verlag, Berlin, E.Elyakova, A.Miroshnikov, V.Bys- 1978, p.159. trov , Yu.Ovchinnikov,Bioorg.Khim. 23. V.Tsetlin, E.Karlsson, Yu.Utkin, _6,840(1980). K.Pluzhnikov, A.Arseniev, A.Suring, 5. V.Bystrov, V.Okhanov, A.Miroshni- V.Kondakov, V.Bystrov,V.Ivanov, kov, Yu.Ovchinnikov,FEBS Lett.l±2> Yu.Ovchinnikovgoxicon, 20,83(1982) . 113(1980). 24. V.Bystrov, V.Tsetlin, E.Karlsson, 6. V.Bystrov, V.Ivanov, V.Okhanov, V.Pashkov, K.Pluzhnikov, V.Kondakov, A.Miroshnikov, A.Arseniev, V.Tset- Yu.Utkin, A.Arseniev, V.Ivanov, lin, V.Pashkov, E.Karlsson, in Yu.Ovchinnikov, Proc.UsS^-Berlin Advances in Solution Chemistry (West) Symp.Neurotoxins as Tools in (I.Bertini, L.Lunazzi, A.Dei.eds) Neuvochem. March 22-24,1983,Berlin Plenum Press,New York,1981,p.231, . (West) (Yu.Ovchinnikov, F.Hucho,eds) 7. V.Bystrov, V.Okhanov, A.Arseniev, W. de Gruyter, Berlin, 1983. V.Afanasiev, 25. T.Miyazawa, T.Endo, F.Inagaki, Khim.6_, 386 (1980). K.Hayashi, 'N.iamiyaJ3iopolymers3 22, 8. V.Okhanov, V.Afanasiev, V.Bystrov, 139(1983). JiAfagn.flee.40,191(1980). 26. 9. V.Bystrov,Progr.NMR Speotr. 10,41 27. M.Walkinshaw, W.Saenger, A.Maelicke, (1976). Proc.Nat.Acad.Sci. USA, 12,2400(1980). 10. V.Bystrov, A.Arseniev, V.Kondakov, 28. I.Nabiev,K.Pluzhnikov, S.Trakhanov, V.Maiorov, V.Okhanov, Yu.Ovchinni- E.Efremov, V.Tsetlin,Bioorg.Khim.]_> kov Proc.USSE-Berlin(West) Symp. 836(1981). Vol. 5. No. 3A 155 29. V.Tsetlin, E.Karlsson, A.Arseniev, Yu.Utkin, A.Surin, V.Pashkov,K.Plu- zhnikov, V.Ivanov, V.Bystrov, Yu.Ov- chinnikov,FEBS Lett. 106,47(1979) . 30. A.Surin, Yu.Utkin, K.Pluzhnikov, V.Tsetlin,Pro<3. USSR-Berlin(West) Symp. Neurotoxins as Tools in Neuro- ohem. March 22-24, 1983,Berlin(West) (Yu.Ovchinnikov, F.Hucho,eds) W. de Gruyter,Berlin,1983. 31. V.Tsetlin, K.Pluzhnikov,A.Karelin, V.Ivanov,Proc. USSR-Berlin(West) Symp. Neurotoxins as Tools in Neuroehem. March 22-24,Berlin(West) (Yu.Ovchin- nikov, F.Hucho, eds) W.de Gruyter, Berlin,1983. Bulletin of Magnetic Resonance FLUORINE NMR SPECTROSCOPY OF PROTEINS M. Cairi, J. T. Gerig*, S. J. Hammond, J. C. Klinkenborg and R. A. Nieman Department of Chemistry University of California Santa Barbara, CA 93106 USA I. INTRODUCTION this atom may be important in a closely- packed protein. In even small proteins the near de- Two convenient ways to introduce generacy of chemical shifts and the fluorine into proteins are by chemical broadening of lines due to rapid trans- modification (1-2) with a reagent con- verse relaxation often conspire to pro- taining one or more fluorine atoms and duce proton and carbon spectra with by biosynthetic incorporation of fluor- large regions that are poorly resolved inated amino acids (3-6). Examples of and largely unassignable. Resolution both approaches are described below; and assignment problems in the proton these illustrate the power of fluorine and carbon spectra of proteins can be substitution to make possible experi- overcome by appropriate isotopic substi- ments that would otherwise be difficult. tutions such as carbon-13 enrichment or We return at the end to the nagging deuteration at specific positions but question of the effects of fluorine sub- these solutions are not always available stitution on protein structure. because of cost or other considerations. Substitution of fluorine for hydrogen II. FLUORINATED HEMOGLOBIN can sometimes be made in a protein. A covalently bound* fluorine is similar in It has been found that the hemoglobin steric requirements to a covalently formed by rabbits receiving D,L-p-fluo- bound hydrogen atom. However, because rophenylalanine in their diet contains of the paramagnetic effect on chemical approximately one fluorophenylalanine shielding and the "exposed" position of residue per tetramer. The primary se- fluorine on the periphery of organic quence of rabbit hemoglobin features molecules, fluorine chemical shifts in eight phenylalanine residues in each a- biological structures are often very and each J|<-subunit; fluorine nmr spec- sensitive to changes in local environ- tra of various forms of this hemoglobin ment. Thus, fluorine spectra of such are consistent with the presence of six- systems may be much better resolved than teen signals (Figure 1), thereby indi- proton or carbon spectra of the parent cating that essentially random substitu- molecule and, because of existing know- tion of fluorophenylalanine for phenyl- ledge of how fluorine was introduced, alanine has taken place and that the may be more rapidly assignable. subunits of a given type are magnetic- The advantages of fluorine substitu- ally equivalent in solution. All fluo- tion in nmr studies of proteins do not rine signals in the spectra of this ma- come without a price, however. Most terial respond to ligation of the heme, serious is the lack of any detailed un- suggesting that ligation must produce derstanding of how fluorine substitution structural changes throughout the pro- might perturb the native three-dimen- tein. Crystallographic studies of this sional structure of a protein; fluorine process in hemoglobins from other spe- is decidedly "unnatural" in these sys- cies show that, while structural changes tems and dipolar or steric effects of clearly accompany ligation, the changes Vol. 5, No. 3A 157 tend to be localized in particular re- proteins must bring together in a selec- gions near the heme groups and at the tive manner those components necessary interfaces between subunits. The fluo- tor the process to be catalyzed and then rinated hemoglobin provides a means to hold them in an orientation that is fa- examine the structural consequences of vorable for reaction. The time scales ligation in solution. for molecular motions near the active Initial efforts at assignment have Site of the enzyme must be consistent utilized the cyancmet form of the pro- with these processes. tein. Assuming a reasonably close Chymotrypsin cleaves peptide and homology between human, horse and rabbit ester bonds by a mechanism that includes hemoglobin, a number of tentative formation of an acylated enzyme by assignments could be made (7). transfer of the acyl group of the sub- strate to the hydroxyl function of serine-195 in the sequence. Structure I c shown below is an excellent substrate for the enzyme; the acylenzyme formed has a very short lifetime under normal catalytic conditions. 0 H H 0 OH 0 II I I II II I II CH3-C-N-N-C-OR CH.-C-N-C-C-OR 3 3 I I CH2 CH, Structure II also rapidly acylates the enzyme but gives a protein that is sta- ble for several days before significant hydrolysis takes place (8); we presume that the structure of this acylenzyme is reasonably similar to that formed in the reaction of I. Structure III is representative of a large family of sulfonyl fluorides which essentially irreversibly acylate the enzyme. m To provide some information on the Figure 1. Fluorine nmr spectra of nature of molecular motion at the active fluorophenylalanine containing hemo- site of chymotrypsin, Tlr T2 and ^F^H) globin from rabbit. A, Deoxyhemoglo- NOEs of the fluorine resonances of the bin; B, Qxyhemoglobin; C, Carbonmonoxy- acylated enzymes produced with II and hemoglobin. Two very broad signals at III have been determined and analyzed. 11.5 and 14.5 ppm are not shown in the The results of these analyses indicate deoxy spectrum. Spectra were obtained that the rate of ring rotation or flip- at pH 7, 25° using solutions about 3mM ping must be less than the rate of over- in protein. all tumbling of the protein. Another view of the flexibility of III. M3TI0N AT THE ACTIVE SITE the active site of acylated chymotrypsin OF AN ENZYME is provided by fluorine nmr studies of acylenzyme IV. In this structure the One likely reason for the rather com- two fluorophenyl groups are magnetically plex nature of enzymes is that these distinguishable. The separation between 158 Bulletin of Magnetic Resonance therefore occur on a timescale somewhere in the broad range between 15 nsec. and 0-Enzyme 8 msec. IV. THE EFFECTS OF FLUORINE SUBSTITUTION the signals is strongly temperature The diphenylcarbamoylchymotrypsin dependent, an observation consistent system provides a means to examine the with either an increase in the rate of influence of fluorine substitution on rotation about the carbonyl carbon- protein structure. If this system is nitrogen bond of the carbamoyl group or constituted so that only one fluorinated reorganization of protein structure as ring is present (V), the enzyme can the temperature changes. The question choose between a phenyl ring and a fluo- of whether or not exchange is present rophenyl ring for each of the environ- ments available to these groups. The was addressed by a two-dimensional ex- fluorine nmr spectrum of the acylenzyme periment (8). (Figure 2). The appearance (V) consists of two broad resonances of cross-peaks in the experiment is definitive evidence for interchange of the environments of the two fluorophenyl N-C groups of the acylenzyme. 0-Enzyme O-Erizyme V representing two environments for the fluorophenyl ring. The down field resonance is about twice as intense as the upfield signal, suggesting that there is only a small free energy difference between the interactions at the two binding sites. Thus a fluoro- phenyl ring cannot replace a phenyl ring in a protein structure with complete im- punity but the energetic and structural ramifications of this change are not large, at least in this system. Figure 2. Two-dimensional exchange spectrum of di(4-fluorophenyl)carbamoyl- chymotrypsin at 5° obtained at 282 MHz. The separation between the peaks in either dimension is 3.95 ppm. Acknowledgement. This work was support- ed by the National Institutes of Health (Grant GM-25975) to whom we express our Interestingly, the dynamics of the appreciation. Departmental instrumenta- rotation are not altered when the pro- tion and the Southern California tein is denatured, although the chemical Regional NNR. Facility used for experi- shifts and relaxation parameters indi- ments at 470 Mhz. were supported by the cate that the tertiary structure of the National Science Foundation. protein has been disrupted (10). Local- ized unfolding of the protein near the active site has to be rapid enough to permit interchange of the fluorophenyl environments at the rate ve observe but slow enough that fluorophenyl ring rota- tion appears to be slower than overall protein tumbling. This change must Vol. 5, No. 159 REFERENCES (1) G.E. Means; R.E. Feeney, Chemical Modification of Proteins, Holden-Day, 1971. (2) A.N. Glazer; R.J. DeLange; D.S. Sigman, Chemical Modification of Proteins, Elsevier, 1975. (3) B.D. Sykes; J.H. Weiner, Magn. Reson. in Biology 1 171-196 (1980). (4) R.E. Marquis, Handbook of Experimental Pharmacology Vol. 20/2, Springer-Verlag, 1980. (5) E.W. Westhead; P.D. Boyer, Biochim. Biophy. Acta 54 145 (1961). (6) M.C.Jarema; J.H. Miller; P.Lu, Proc.Natl.Acad.Sci.U.S. 78 2707 (1981). (7) J.T. Gerig, J.C. Klinkenberg and R.A. Nieman, Biochemistry, in press. (8) S. Barker; C.J. Gray; J.C. Ineson; R.C. Parker; J.V. McLaren, Biochem. J. 139 553-563 (1974). (9) J. Jeener, B.H. Meier, P. Bachman, and R.R. Ernst, J. Chem. Phys. 71 4546-4553 (1979). (10) M. Cairi and J.T. Gerig, J. Am. ChenuSoc., in press. 160 Bulletin of Magnetic Resonance P-31 NMR OF NUCLEIC ACIDS David G. Gorenstein Department of Chemistry University of Illinois at Chicago Chicago, Illinois 60680 I. INTRODUCTION states are much more limited as to back- bone flexibility, and generally the We have proposed that 31P chemical phosphate diester conformation is lim- shifts in phosphate esters may serve as ited to g,g (10). The 31P NMR spectra a direct probe of P-0 ester bond tor- of multihelical nucleic acids will hope- sional angles. Both theoretical consid- fully provide better information on the erations (1-5) and direct experimental 31P chemical shift of a purely g,g phos- tests of this hypothesis (6~9) confirm phate diester. Unfortunately, the 3XP that the 31P signal of a phosphate dies- NMR signal of multihelical polymers at ter monoanion in a gauche, gauche (g,g) lower temperatures is often too broad to conformation (as found in the helix be very useful or even observable. To state) should resonate several parts per avoid this problem we have therefore million upfield from a diester in a non- chosen to study a mixture of complemen- gauche conformation (as found in the tary oligouridylic acid (oligo U) and random coil state). polyadenylic acid (poly A), or sonicated These conclusions prove to be espe- mixtures of complementary polymers cially significant since other spectro- (e.g., poly A + poly U). These polymer- scopic probes fail to provide detailed oligomer complexes or short (200 base conformational information on the phos- pair) double-helical polymers tumble phate ester bonds in the nucleic acids. sufficiently rapidly in solution to give Since it is now believed that of the six high resolution spectra. torsional angles that largely define the The temperature dependence of the 31P conformational structure of nucleic spectra and chemical shifts of a 1:1 acids, the two P-0 ester torsional mixture of poly A and oligo U is shown angles provide the main conformational in Figure 1. At temperatures of 50°C or flexibility to the nucleic acid backbone higher 31P spectra correspond largely to (10). Thus 31P NMR can monitor the the superposition of the component poly "helix-coil" transitions in single- A and oligo U spectra. Most signifi- stranded nucleic acids (6,11). A large cantly, below the melting temperature, 3i (0.7-1.3 ppm) downfield shift for a wide Tm~55°C, a new P signal is observed, structural range of nucleic acids was 0.4-0.6 ppm upfield from the 31P signal observed upon raising the temperature. of the poly A or oligo U species free in At low temperature the nucleic acids solution. This signal corresponds to exist largely in a base stacked, helical the double helix, poly A*(oligo U)n or conformation with the phosphate ester triple helix, poly A»2(oligo U)n. predominantly in the g,g conformation, The assignment of this new upfield while at higher temperatures the nucleic signal to the double helical (and/or- acids largely exist in random coil, triple helical state is suggested by [l] unstacked conformations with the phos- the signal broadness and [2] the sharp phate ester in an increased proportion transition for its melting. of nongauche (i.e., gauche, trans (g,t), 1. Phosphorus line widths. The etc.) conformations. downfield signal we have assigned to oligo U stays quite narrow (<5Hz at 32.4 II. DOUBLE-STRANDED NUCLEIC ACIDS MHz) over the temperature range of 25-65°C. It is only slightly broader The double helical and triple helical (7-8 Hz) at 146 MHz. The poly A signal Vol. 5, No. 3A 161 POLY A-OLIGO U (1:1) POLY A : OLIGO U (1:1) 35 45 SS 65 75 85 °C -1.0 -1.5 Figure 1. 31P NMR spectra for poly A + poly U mixture (1:1) at various tempera- tures, pH 7, 20% DsO, 0.2 M NaCl, 10 mM cacodylate, 1 mM EDTA, 24 mg/ml total nucleotide, (a) Referenced to 15% H3PO4 in D2O (internal lock), which is 0.453 ppm upfield from 85% H3PO4 with capillary D2O lock. (b) Plot of 3XP chemical shifts vs temperatures for spectra in Figure la [from (1)3. is also only slightly broader at 32 MHz over this temperature range (3~8 Hz) but is substantially broader at 146 MHz T> (20-30 Hz). The upfield double (triple) helix signal is still broader. At 32 MHz it is 6-9 Hz, whereas at 146 MHz it where r is the lifetime of the exchang- increases from 50 Hz to 109 Hz as the ing nuclei and Ay is the chemical shift temperature is lowered (1,5). difference in Hz between the two states. The polymeric, multistranded helix Since Av~20 Hz (at 32 MHz) for the poly will be much more rigid than the poly A A»oligo U single to multistrand single helix, and the rotational motion exchange, r>8 msec. of the molecule will be greatly reduced. These conclusions are supported by This shortens the 31P transverse relaxa- the 31P NMR spectra of sonicated poly tion time and broadens the signal. A»poly U (see Lai et al., this Bulle- 2. 31P Melting curves. The 31P tin) . The 200 base-pair double helix is melting profile (Figure lb) for the more stable than the poly A«poly U helix 31 upfield signal shows a sharp melting and thus the upfield (g,g) P signal is transition, characteristic of a coopera- correspondingly larger. tively melting multistranded species. To our knowledge these 3XP NMR studies III. 31P NMR OF TRANSFER RIBONUCLEIC represent the first time separate NMR ACIDS signals for the multistranded state and single-stranded state have been Gueron & Shulman (9), Gorenstein & observed. For this to be possible, Luxon (7), and Salemink et al (12), have chemical exchange of the nucleic acid shown that the high resolution 31P NMR components between the single and mul- spectra of transfer RNA contains consid- tistranded states must be slow on the erable fine strucutre. A number of NMR time scale, or ' individual phosphate resonances could 162 Bulletin of Magnetic Resonance even be resolved that were not revealed 30°. Other scattered signals become in earlier 31P spectra at nonsupercon- better resolved at different tempera- ducting fields. A comparison of the 31P tures. Individually resolved signals NMR spectrum of yeast tRNAPhe and E. (such as B, C, and T) integrate in all coli tRNAflu, tRNATvr, and tRNAs for ~1 phosphate. tRNAfMet, and bovine liver tRNAAsP The temperature dependence of the 3XP in 10 mM Mg2* buffer, ~30°C is shown in chemical shifts of the signals is quite informative. Between 20 and 60cC most of the scattered and main cluster sig- nals shift very little with temperature. As shown earlier (7) this temperature insensitivity to most features in the t-RNA 31P spectra in 10 mM Mg2* suggests that the tRNAs (and the backbone phos- phates) largely retain their native con- formation throughout this temperature range. Eventually at T>T,n~60 to 75°C, all of the diester peaks merge into a single signal with the tRNA melt- ing into a random coil conformation. These scattered signals have been assigned to phosphates in geometries distorted by the tertiary folding of the tRNAs. Measured spin-lattice and spin- spin relaxation times for tRNArne (7,13) reveal another lower temperature transition associated with a conforma- tional change of the anticodon loop besides the thermal denaturation pro- 0 ppM -2 -X -6 cess. A number of the scattered peaks Fig. 2. 31P NMR spectra of yeast are shifted (0.2-1.7 ppm) and broadened tRNAPhe (top) and E. coli tRNA1?1" between 22 and 66°C in the presence of (middle) and tyrosine-phenylalanine dif- Mg2* as a result of this conformational ference 31P NMR spectrum (bottom) at transition. The effects of Mg2* and 35°C, pH 7, 10 mM MgCls, 100 mM NaCl, 10 Mn2* ions on the 31P NMR spectra of mM cacodylate, 207. D2O, 1 mM EDTA, 80.9 tRNAP"e as well as nuclease treatment MHz (31P) and 2 Hz line broadening (12) have been used to identify some of applied to FID. the scattered signals upfield and down- Figs. 2 and 3. field from the main cluster signals. The tRNA's show a number of similar spectral features. Thus between +3.1 ACKNOWLEDGEMENTS and +3.4 ppm is the 3'-terminal phos- phate which integrates for a single Supported by research grants from the phosphate residue and is the only signal National Institutes of Health and the which is pH sensitive (being a monoester National Science Foundation. Purchase with pK~6). Between 0 and 1.5 ppm is a of the Bruker WP-80 and IBM 200 SY Spec- main cluster of signals representing the trometers was assisted by National Sci- undistorted phosphate diesters in the ence Foundation Departmental Equipment double helical stems and hairpin loops. Grants. Support of the Purdue Biologi- The main cluster peaks L/M for the heli- cal NMR facility by NIH (RRO 1077) is cal stems integrate for 35 to 37 phos- acknowledged. We thank Bruce Luxon, phates in all the tRNAs. Upfield and Rouhlwai Chen, Evelyn Goldfield, and downfield of the main cluster, spread Kofen Lai for their contributions to the over 6-7 ppm are ~16 scattered signals, studies described in this paper. of which a number are well resolved at Vol. 5, No. 163 REFERENCES (1) D. G. Gorenstein and K. Kar, Bio- chem. Biophys* Res. Commun. 65, 1073 (1975). (2) D. G. Gorenstein, _J. Am. Chem. Soc. 97, 898 (1975). (3) D. G. Gorenstein, Jerusalem Symp. Quantum Chem. Biochem. 11, 1 a : f Met (1978). (4) D. G. Gorenstein, Annu. Rev. Bio- phys. Bioeng. 10, 355, (1981). (5) D. G. Gorenstein, In "P-31 NMR: Principles and Applications" (D. G. Gorenstein, Ed.) Academic Press, New York, 1983. (6) D. G. Gorenstein., J. B., Findlay, R. K., Momii, B. A., Luxon, and D. Kar, Biochemistry 15, 3796 (1976). (7) D. G. Gorenstein and B. A. Luxon, Biochemistry ]J5, 3796 (1979). (8) D. J. Patel, Ac_c. Chem. Res. 12, 118 (1979). (9) M. Gueron and R. G. Shulman, Proc. Natl. Acad. Sci. U.S.A. 72. 3482 (1975). (10) S. H. Kim, H. M. Berman, N. C. Seeman, and M. D. Newton, Acta CrystalloRr., Sect. B 29, 703 (1973). (11) C. A. G. Haasnoot and C. Altona, Nucleic Acids Res. 6, 1135 (1979). (12) P. J. M. Salemink, T. Swarthof, and C. W. Hibers, Biochemistry 18, 3477 (1979). (13) D. G. Gorenstein and E. M. Gold- field Biochemistry 2_1, 5839 (1982); J. Mol,. Cell. Biochem. 46, 97 (1982). •4 Fig. 3. Comparison of 31P NMR spectra of bovine liver tRNAAsP (a), E. coli tRNA^Met (b), tRNATvr (c), and lu tRNA?. (d), and yeast tRNAPh. (e) at pH 7,207. D20, 10 mM MgCl2, 0.2 M NaCl, 10 mM cacodylate, 1 mM EDTA, 31° C (except tRNAGlu at 35°C), and 32.4 MHz with 0.5 Hz spectral line broadening. 164 Bulletin of Magnetic Resonance THE DYNAMIC STRUCTURE OF NUCLEIC ACIDS Thomas L. James, Peter Bendel, Joe W. Keepers, and John E. Taylor Department of Phamaceutlcal Chemistry, School of Pharmacy, University of California, San Francisco, CA 94143 The conformational flexibility of We can therefore test the capabi- DNA is important because of its proba- lity of these postulated motions to ble influence on DNA replication, account for the NMR relaxation data. transcription, translation, and recog- As we have described (5), the relaxa- nition. NMR studies and x-ray crys- tion mechanisms due to chemical shift tallography have been primarily res- anisotropy and dipole-dipole interac- ponsible for the recent concept of a tions can be used with calculated non-rigid double helix capable of spectral densities for a large variety conformational variations and a signi- of amplitudes and frequencies of the ficant degree of motional freedom. postulated motions; internuclear The conformational variants may exist distance fluctuations as well as for a long time or may exist tran- reorientation can be explicitly incor- siently. porated into the spectral densities. We (1-6) and others (7-12) have Our work has shown that double- utilized NMR relaxation in an effort stranded nucleic acids of length >600A to elucidate the molecular motions in possess a motion on the microsecond nucleic acids. NMR relaxation para- time scale, which can most reasonably meters are sensitive to the motional be attributed to bending (1,2,6). frequencies and, to a lesser extent, Nanosecond motions in the backbone the motional amplitudes. NMR relaxa- have been inferred from *P and "C tion does not, however, directly NMR relaxation measurements (1-3,6- reveal the nature of the motions. We 8). Analyzing the results in terms of have taken the approach that basic the plausible motions described above knowledge of the double helical struc- revealed that torsional twisting, base ture limits the list of plausible tilting, and base pair propeller molecular motions in double helical twisting motions have little effect on DNA. Most of the feasible motions are NMR relaxation of backbone nuclei illustrated in Figure 1. (5). Experimental C relaxation results of carbons in the deoxyribose "SPEEDOMETER CABLE ROTATION ring could be predicted by ring puck- ering motions of amplitude 70°, but the C5' and P relaxation required additional rotations in the backbone torsion angles on the order of 50°. Using the frequencies and ampli- tudes of the motions suggested by the NMR analysis, molecular mechanics calculations were carried out (13). TRANSITORY STRAND These calculations indicate that from SEPARATION "BUEATHINO the viewpoint of molecular energetics, there is no reason for the motions to be concerted along the length of the Figure 1. Plausible motions in a DNA; rather, the internal motions are double helical nucleic acid. highly localized with compensations Vol. 5. No. 3/i» 165 being made within a few bonds of any relaxation. induced bond rotation (for example A considerable amount of naturally- 1,3-crankshaft motions are common). occurring DNA is in the form of super- In the first 15N NMR study of DNA, helical or covalently closed duplex the spectra suggested that the base DNA (cdDNA), which displays some moiety experienced internal motions unique properties of chemical and restricted in amplitude or frequency biological activity (14). We recently relative to those of the backbone obtained the first NMR results from an (4). We have subsequently performed intact plasmid, the cdDNA being N relaxation experiments at three plns36, a 7200 base pair, 5 megadalton different magnetic field strengths for plasmid containing the human insulin uniformly 15N-enriched DNA. As seen gene (6). P NMR relaxation experi- in Figure 2, nearly all the nitrogen ments indicated that the internal motions in the phosphodiester moiety are about the same for linear, nicked circular, and supercoiled forms of plns36. But the slower motion govern- ing To relaxation is about two orders of magnitude faster in cdDNA compared with linear DNA. We suggested that the increased rate of motion may be due to coupling the bending motion effecting relaxation to higher fre- quency torsional motions, the coupling being necessitated by connecting the ends of the DNA strands. 31 The large P T2 measured for —I—' pins36 suggested that relatively high 100 resolution proton NMR spectra might be obtained. That is indeed the case as Figure 2. 15N NMR spectrum (24.4 MHz) seen in Figure 3. The line widths of of 15N-labeled DNA (27 mg/ml) in 40 mM the imino resonances of pins36* (Fig; sodium cacodylate, pH 7.2 and 40 mM 3c-e) are narrower than those of NaCl at 20°C. Spectral parameters: linear DNA ~ 20 times shorter (Fig. 10,000 transients, 70° pulses, 0.65 4a) and much narrower than linear DNA sec acquition time, 3.0 sec repetition of comparable length (Fig. 4b). time, 10 Hz exponential line broade- Based on previous studies (8,15), ning, broadband proton decoupling on the band centered at 12.6 ppm in the during acquisition. (B) N spectrum cdDNA spectrum can be assigned to of DNA simulated from chemical shifts imino protons of G-C base pairs and of individual nucleotides. those at 14.3, 14.0, and 13.2 ppm can be assigned to A-T base pairs. Al- resonances are resolved. This pro- though the G-C resonance position is vides a large amount of data which any unchanged relative to linear DNA, the base moiety motional model is required A-T resonance region exhibits discrete to fit. We have considered a number peaks with the major part clearly of possible molecular motions as shifted relative to that of linear potential contributors to *% relaxa- DNA. The small peak at 14.0 ppm is tion. Calculations to date indicate probably due to a small amount of that torsional twisting motions will nicked circular DNA evident from gel be inadequate, but that base tilting electrophoresis of the sample. motions approximately an order of Our prior molecular mechanics magnitude slower than the backbone calculations indicated that some A-T motions will account for the N base pairs, but no G-C base pairs, 166 Bulletin of Magnetic Resonance contributions from ring current and atomic magnetic anisotropy effects were calculated (16). Although we do not have definitive experimental evidence for such a "base-open" A-T state, they apparently would be formed more easily in supercoiled DNA and could account for a peak a 14.3 ppm. (Research supported by NIH grants GM25018, CA27343, and Research Career Development Award AM—291 to TLJ.) REFERENCES 1. P.H. Bolton and T.L. James, J. Phys. Chem. 83, 3359 (1979). 2. P.H. Bolton and T.L. James, J. Am. Chem. Soc. 102, 25 (1980). 3. P.H. Bolton and T.L. James, Bio- chemistry 19, 1388 (1980). 4. T.L. James, J.L. James and A. La- pidot, J. Am. Chem. Soc. 103, 6748 (1981). 5. J.W. Keepers and T.L. James, J. Am. Chem. Soc. 104, 929 (1982). 6. P. Bendel, 0. Laub and T.L. James, J. Am. Chem. Soc. 104, 6748 (1982). 7. L.-Klevan, I.M. Armitage and D.M. Crothers, Nucl. Acids Res. 6, 1607 Figure 3. Proton NMR spectra of (a) (1979). 200-700 bp calf-thymus DNA, 240 MHz, 8. T.A. Early and D.R. Reams, Proc. 24°C, (b) 0.6-10 Kbp calf-thymus DNA, Natl. Acad. Sci. U.S.A. 76, 4165 240 MHz, 24°C, (c) supercoiled plns36, (1979). 240 MHz, 24°C, (d) supercoiled plns36, 9. M.E. Hogan and 0. Jardetzky, Bio- 240 MHz, 11°C, and (e) supercoiled chemistry 19, 3460 (1980). plns36, 360 MHz, 24°C. The spectra 10. H. Shindo, Biopolymers 19, 509 were obtained using modified Redfield (1980). pulse sequences. 11. R.L. Rill, P.R. Hilliard, Jr. , J.T. Bailey and G.C. Levy, J . Am. could be trapped in a state with non- Chem. Soc. 102, 418 (1980). Watson-Crick hydrogen bonding (13). 12. S.J. Opella, W.B. Wise and J.A. This "base-open" state subsequently DiVerdi, Biochemistry 20, 284 was calculated to form more readily (1981). when the double helix was underwound 13. J.W. Keepers, P.A. Kollman, P.K. relative to linear DNA, just as cdDNA Weiner and T.L. James, Proc. Natl. is. Using the coordinates from an Acad. Sci. U.S.A. 79, 5537 (1982). energy-refined dodecamer with a "base- 14. W.R. Bauer, Annu. Rev. Biophys. open" A-T pair the imino proton Bioeng. 7, 287 (1978). chemical shifts were calculated to be 15. D.R. Kearns, Annu. Rev. Biophys. 1.0 ppm downfield for the "base-open" Bioeng. 6, 477 (1977). A-T pair and 0.5 ppm downfield for the 16. D.B. Arter and P.G. Schmidt, Nucl. adjacent base pair; the chemical shift Acids Res. 3, 1437 (1976). Vol. 5, No. 3A 167 ACCESSIBILITY OF THE ACTIVE SITE IN METALLOPROTEINS TO AMBIENT WATER AS DETERMINED BY ELECTRON SPIN ECHO ENVELOPE SPECTROSCOPY W.B. Mims , J. Peisach"* '+ * and J.L. Davis Bell Laboratories, Murray Hill, NJ 07974 and Albert Einstein College of Medicine, Bronx, NY 10461 I. INTRODUCTION Rhus vernicifera, and azurin from Pseudomonas aeruginosa were recorded The periodic modulation patterns before and after DoO exchange lasting observed in the electron spin echo 2 to 3 hours. "Envelopes obtained decay envelope (1) can, via Fourier with DoO-exchanged azurin, for exam- transformation, (2) be made to yield ple, (rig. 1A) were then divided by information similar to that obtained the corresponding envelopes obtained in an ENDOR experiment (3,4). The with the initial D20-free material depth of the patterns is also a (Fig. IB) in order ±o isolate the source of useful information (Ref. 1, contribution due to H (Fig. 1C) and Eqs. 27-30). For weakly coupled nu- to minimize other modulation compo- clei, such as the hydrogen in water nents. An antiphase H1 modulation coordinated complexes, the modulation component in the quotient function, depth yields the product n/r° where n indicating protons displaced by is the number of equivalent nuclei deuterons, was removed by filtering. and r the radial distance. Further- more, in the case of frozen solution III. RESULTS samples, the decay rate of the mod- ulation pattern may yield yet add- The best results, in the case of itional information. For example, the copper proteins, was obtained in for H the decay rate depends pri- the three-pulse experiments, (Fig. 1) marily on the electron nuclear coup- with the time "V between pulses I and ling and is ^ 1/r . One can there- II (6) selected at 220 nsec so as to fore discriminate between modulation minimize a strong N component (Ref. components due to a few nuclei close 3, pp. 241-243) arisina from imid- by (large coupling, rapid decay) and azole ligands of the Qr+ ion (5,8- modulation components due to many nu- 10). After envelope division these clei further away (weak coupling, measurements gave a reasonably clean slow decay). The situation is simi- H^ modulation pattern (1) which could lar for H^ although consideration be fitted to a model cosine in order must be given here to the quadrupolar to determine the modulation depth. interaction which also contributes to the decay of the modulation pattern IV. DISCUSSION (4). Results were interpreted by making II. METHODS a comparison with the H modulation patterns observed for partiaTLy deu- We have used measurements of the terated Cir+:aquo (1) and NdJ+:aquo modulation depth to study the deuter- (11) complexes. The modulation decay ation of the environment of the ac- rates for the copper proteins were tive site when copper proteins are considerably slower than those ob- exposed to DoO. Two-pulse (5) and served for Cu :aquo and were more three-pulse 05) echo envelopes for comparable with those observed for laccase (7) and stellacyanin (5) from Nd :aquo. Although we were not able to make quantitative analyses of the 168 Bulletin of Magnetic Resonance i i i i i 1.00 ~,n A AZURIN active sites are situated in a crev- \ r\ 3-pulse ice which is partially accessible to solvent. This result is unsurprising in the case of the oxidase laccase, 0.50 which requires accessibility of the active site to 02, but it is of some interest in the case of azurin (and 0 H2O B also of stellacyanin) which serves to x transfer electrons, and for which it T 22Onsec had previously been supposed from ! 1 1 ! 1 X-ray crystallographic analysis that the active site was buried beneath 1.0 - the surface of the protein molecule (12, 13). Our results suggest that (l/l M, A n lJ^r^J\ r the active site in this protein is 0.9 - more accessible to solvent when in solution than in the crystalline state. The accuracy with which the elec- 0.8 V. tron nuclear distance r was deter- 1i 2 i 3i 4i i mined in these experiments is esti- T+r(/xsec) mated to be _+ 12%. The uncertainty arises because of the rapidity of de- cay of the modulation pattern, and FIGURE 1 because of the need for making mea- surements one or two cycles from the Three-pulse electron spin echo start. Substantial improvements may decay envelope of azurin. Curve A be anticipated here as more attention shows the ESE envelope after exchange is given to the study of suitable against DoO. Curve B shows the enve- model complexes with better defined, lopes obtained for the same sample more rigid structure than the hydrat- before DpO exchange. The modulation ed metal ions. component due to exchanged deuterium The technique offers a new method can be seen in the C-curve, which was for studying the structure of protein obtained by dividing the B-curve into active sites and their accessibility the A-curve. Measurements of the to solvent. It has the advantage peak-to-trough amplitudes in the that the geometrical disposition of deuterium modulation pattern are used the protein is not modified by crys- to estimate how close the exchanged tal packing forces. The technique is DoO molecules and deuterons are to not only applicable for the study of the Cu active site. Data were H2, but cao.be used for ±he measure- taken at liquid He temperatures with ments of C13 (14,15), P6L (2,16) and a spectrometer frequency of 9507 MHz Na^J (2) modulation, to examine a and a magnetic field setting of variety of other biological systems 3293 G. in which these nuclei occupy posi- tions in the close vicinity of para- decay rates, the distinction between magnetic centers. the Cu2+:aquo and the copper protein data was sufficiently clear to enable V. ACKNOWLEDGEMENT us to conclude that exchangeable hy- drogen in the copper proteins cannot That portion of this work carried be assigned to a single closely co- out at the Albert Einstein College of ordinated water ligand to the metal Medicine was supported in part by the ion. Instead, it appears that the U. S. P. H. S. grant HL-13399 to J.P. Vol. 5, No. 3A 169 REFERENCES 1. W.B. Mims, J. Peisach, and J.L. 10. L. Ayigliano, J.L. Davis, M.T. Davis, J. Chem. Phys., 66, Graziani, A. Marchesini, W.B. 5536, 1982. Mims, B. Mondovi, and J. 2. T. Shimizu, W.B. Mims, J. Peisach, FEBS Lett., 156, 80, Peisach, and J.L. Davis, J. 1981. Chem. Phys. 70, 2249, 1979 11. W.B. Mims, and J.L. Davis, J. 3. W.B. Mims, and J. Peisach, Chem. Phys. 64, 4836, 1976. Biological Magnetic Resonance, 12. E.T. Adman, R.E. Stenkamp, L.C. Vol. 3, L.J. Berliner and J. Sieker, and L.H. Jensen, J. Reuben, editors, Plenum Press, Mol. Biol., 123, 35 1978. New York, 1981, pp. 213-263. 13. P.M. Colman, H.C. Freeman, J.M. 4. S.A. Dikanov, Yu. D. Tsvetkov, Guss, M. Murata, V.A. Norris, A.V. Astashkin, and A.A. J.A.M. Ramshaw, and M.P. Shubin, J. Chem. Phys. 1983, in Venkatappa, Nature (Lond.), press. 272, 319, 1978. 5. W.B. Mims, and J. Peisach, 14. J. Zweier, P. Aisen, J. Biochemistry, 15, 3863, 1976. Peisach, and W.B. Mims, J. 6. J. Peisach, W.B. Mims, and J.L. Biol. Chem., 254, 3512, 1979. Davis, J. Biol. Chem., 254, 15. J. Zweier, J. Peisach, and W.B. 12379, 1979. Mims, J. Biol. Chem., 257, 7. J. Peisach, W.G. Levine, and 10314, 1982. W.E. Blumberg, J. Biol. Chem., 16. T. Shimizu, W.B. Mims, J.L. 242, 2847, 1967. Davis, and J. Peisach, Biochim. 8. W.B. Mims, and J. Peisach, J. Biophys. Acta, 1983, in press. Biol. Chem., 254, 4321, 1979 9. B. Mondovi, M.T. Graziani, W.B. Mims, R., Oltzik, and J. Peisach, Biochemistry, 16, 4198, 1977. 170 Bulletin of Magnetic Resonance CLINICAL APPLICATION OF PROTON NMR IMAGING I R Young1 and G M Bydder2 Picker International Wembley, Middx., UK 2 Royal Postgraduate Medical School Hammersmith Hospital London, UK Proton nuclear magnetic resonance is myocardium of the heart and experimental the latest addition to medical imaging infarction can be demonstrated. The technology. Clinical experience is sensitivity of NMR images to changes in still limited but it now appears likely flow is of value in demonstrating that this technique may come to play a obstruction or occlusion of vessels and significant role in neurological in allowing the demonstration of diagnosis, and possibly in other areas atheromatous plaque in major vessels (3). of the body as well. In spite of respiratory movement Classical NMR pulse sequences are during the 2-4 minute scan time causing used to produce images with varying blurring the high level of soft tissue dependence on proton density Ti and T2« contrast on IR images enables the liver Spatial encoding is achieved with to be seen with considerable clarity. magnetic field gradients and image The pancreas has a T-| value slightly reconstruction is either by projection- greater than that of the liver and reconstruction or two-dimensional disease process such as tumor and Fourier transform. pancreatitis increase this. Cerebral infarction produces an The most striking feature about increase in T-| and T2 and a loss of kidney images is the differentiation grey white contrast with inversion- between cortex and medulla. Loss of recovery (IR) scans. NMR imaging is of this contrast is seen in a variety of most value in showing brainstem and diseases. cerebellar infarction where There is little doubt that abnormalities on CT scans are frequently improvements in NMR quality will obscured by bone artefact (1, 2). continue over the next few years. In Acute hemorrhage displays a short T particular, increased spatial resolution 1* In addition, central areas of in the body may result in a more liquefaction or clot dissolution are significant role for NMR. seen. The lesions of multiple sclerosis are well demonstrated with NMR in their characteristic periventricular sites. Cerebral tumors generally show an increase in Ti and To although tumors containing lipid may have a short T^. Cerebral edema displays an increase in T-| and T2 and in a proportion of cases there may be difficulty in distinguishing tumor from edema. The high level of grey white matter contrast available with IR sequences provides a basis for the demonstration of the normal process of myelination in infants in vivo (3). Delays in this development can also be seen. Blood can be distinguished from Vol. 5, No. 3A 171 REFERENCES 1. G M Bydder, R E Steiner, I R Young, A S Hall, D J Thomas, C A Pallis, N J Legg. AJR 139: 215-236 1982 2. G M Bydder R E Steiner, D J Thomas, J Marshall, D J Gilderdale, I R Young. Clin Rad 34: 173-188 1983 3. L Kaufman, L Crooks, S Sheldon, H Hricak, R Herfkens, W Bank Circulation 67: 251-257 1983 Bulletin of Magnetic Resonance Instrumentation in NMR Imaging Lawrence E. Crooks, Ph.D. University of California, San Francisco Radiologic Imaging Laboratory 400 Grandview Drive South San Francisco, California 94080 I. INTRODUCTION signals emitted by protons after irradiation with an RF pulse will General reviews of NMR imaging are reflect their position. available in references 1, 2, 3, and 4. Proton NMR imaging produces NMR is performed in a strong, uniform images that represent one or more of and very stable magnetic field. All four parameters. These are hydrogen NMR imagers that produce anatomic density, the state of motion of the representations of the human body use hydrogen, and the tissue relaxation a sequence of RF pulses and times Tl and T2. manipulations of the magnetic field. These processes take time, maybe a NMR imaging is based on the magnetic total of 20 to 60 msec. The sequence properties of protons, which spin and is designed to obtain a desired act as magnetic dipoles. Placed in a response from nuclei within a certain strong magnetic field, they become volume. If the nuclei move across aligned, producing a net magnetic that volume during this time, they vector, or moment, oriented parallel will be subject to a different set of to the direction of the imposed events, and their signal will differ magnetic field. Application of a from that which they would emit if radiofrequency (RF) pulse of a they were stationary. specific frequency displaces the net magnetic moment by an amount This is just one example of the determined by the strength and versatility associated with the NMR duration of the pulse. This imaging process. Other examples frequency is directly proportional to abound. For instance, by changing the strength of the magnetic field, the order in which the x, y and z and is known as the resonant gradients are applied, images can be frequency. After the pulse, the obtained in the coronal and sagittal protons can produce an RF signal as planes. By triggering the start of they return to their original each projection with an orientation. When a gradient is appropriately-synchronized signal, introduced in the magnetic field, the gated images of the heart are resonant frequency of protons in a realized. Spatial resolution is sample placed in the gradient will changed by varying gradient strength, vary with their position in the and so on. All this is accomplished gradient. Thus, the frequency of the through software instrumentation, so Vol. 5, No. 173 that the methodology can continue to over the body, and stability) improve with the same hardware base. permanent magnets need to be large and heavy and maintained at a II. HARDWARE FOR NMR IMAGING constant and uniform temperature. NMR imaging of humans has been The physical characteristics of the performed with two other kinds of NMR imager are dictated by the needs magnets. The simplest and cheapest of the technique: A strong, uniform, to build are air core resistive and stable magnetic field has to be magnets. These magnets were used imposed over a portion of the almost universally in early human NMR subject. This field has to be varied imaging (our own effort being in space and time to define the probably the sole exception), but location of nuclei, RF has to be have some disadvantages: The field delivered to and detected from the strength approaches 0.2T only with subject. Finally, the imaging difficulty, 0.12-0.15T being more process, data acquisition, reduction common, field uniformity over and display has to be controlled. body-sized objects is poor, stability is suboptimal, and 60-80 KWatts of Theoretical considerations predict power are needed to drive the that the NMR signal (S) will vary as magnets. The power requirements are S -v* H2, where H is the strength of continuous, and to dissipate the the magnetic field. Since noise (N) current-generated heat there exists a is expected to increase only with the need for large heat exchangers and square root of H, the signal to noise significant water consumption. A level achievable should vary as S/N ^ practical solution to these problems H3'2. By itself, this factor would is presented by superconducting lead to choosing high magnetic fields magnets, even through they introduce for imaging purposes. Other factors other problems. In a superconducting contribute to limit the field magnet, once a current is established intensities that can be used. One of its decay rate is dependent only on these is absorption in the body of manufacturing imperfections, and the RF energy used for excitation of because efficient use of current is the nuclei in the subject and later not important these imaging magnets emitted by these excited nuclei (Ref are typically wound in a solenoidal 5). This absorption increases as RF shape. The coils are kept at low frequency increases, i.e., at higher temperatures by partial immersion in magnetic fields. A second factor a liquid helium bath, care being involves the design of the coil that taken in minimizing heat leakage by is used as a transmitting and providing vacuum insulation and an receiving antenna for the RF (Ref 6). intermediate temperature shield kept Predictions based on antenna and cold by liquid nitrogen. These absorption limitations indicate that magnets provide fields of 0.3-0.5 T whole body imaging might be difficult over human sized volumes, uniformity above frequencies of 8-10 MHz, exceeding 100 ppm and the decay rate corresponding for hydrogen to being a small fraction of a ppm/hr. magnetic fields of 0.19-0.23T (5). As mentioned previously, these excellent imaging characteristics are A magnetic field can be imposed accompanied by certain disadvantages either by a permanent magnet, or by when comparing superconducting to electric currents. Permanent magnets resistive magnets: Purchase price is are appealing because of their higher. Installation is more simplicity, but to meet the triad of difficult, since the magnets cannot needs (field strength, uniformity be disassembled into separate coils, Bulletin of Magnetic Resonance and one is faced with moving what III. REFERENCES essentially is a 2.5 m cube. The 1. Kaufman L, Crooks LE, and weight, which is around 5,000 kg, is Margulis AR, eds. Nuclear Magnetic in the range of some CT scanner Resonance Imaging in Medicine. gantries. Finally, the cost of the Igaku-Shoin, New York, 1981. cryogens used to keep the magnet cold 2. James EA, Partain LC, Holland NG, offsets the savings in electricity et al: Review: Nuclear Magnetic and water in resistives. Resonance Imaging: The Current State. James et al. AJR 138:201-210, 1981. The first human head image was done 3. Loeffler W and Oppelt A: by EMI (Ref 7) in a resistive magnet. Physical Priniciples of NMR Until 1981 all human imaging was done Tomography. Europ J Radiol 1:338 at field strengths varying from 0.05 (1981). to 0.15 T in resistive magnets (Ref 4. Pykett IL, Newhouse JH, Buonanno 8,9,10) with the exception of EMI who FS, et al: Principles of Nuclear had a superconducting magnet at magnetic resonance imaging. Hammersmith hospital operating at Radiology 143:157-168, 1982. 0.15T (Ref 11). We published the 5. Bottomley PA, Andrew ER: RF first images using a superconducting Magnetic Field Penetration, Phase magnet at a field of 0.35T (Ref 12). Shift, and Power Dissipation in The quality of the contrast and Biological Tissue: Implications for resolution of these and subsequent NMR Imaging. Phys Med Biol 23: images indicated that the problems of 333-347, 1978. higher frequency coil design and 6. Hoult DI, Lauterbur PC: The radio frequency penetration of the Sensitivity of the Zeugmatographic body were not preventing achievement Experiment Involving Human Subjects. of better performance at higher J Mag Reson 34: 425-433, 1979. fields. With this expectation of 7. EMI Central Research Laboratories better performance at higher fields, in Britain Produces Cross-Sectional manufacturers are moving toward 0.5T Head Scan by NMR. Radiology/Nuclear and higher. Medicine February 1979. 8. Mansfield P, Pykett IL, Morris Presently it appears as if PG, et al: Human Whole Body Line-Scan superconducting magnets will be Imaging by NMR. Brit J Radiology, offered by all major manufacturers of 51:921-922 (1978). NMR imagers. Resistive magnets will 9. Edelstein WA, Hutchison JMS, also be offered commercially, but Johnson G, et al: Spin Warp NMR they are likely to have a secondary Imaging and Applications to Human role in the U.S. and Western Europe Whole-Body Line-Scan Imaging. Phys (England excluded), where the history Med and Biol. 25:751-756 (1980). of other imaging technologies 10. Hawkes RC, Holland GN, Moore WS, demonstrates that capital costs are et al: Nuclear Magnetic Resonance secondary to performance, (NMR) Tomography of the Brain: A reliability, and non-obsolescence. Preliminary Clinical Assessment with Although liquid helium can be made Demonstration of Pathology. JCAT available in any country in the world 4(5)-.577-586, 1980. by fractional increases in costs due 11. Doyle FH, Pennock JM, Orr JS, et to transportation, in places where al: Imaging of the Brain by Nuclear import charges and/or customs Magnetic Resonance. The Lancet inefficiencies make cryogens 53-57: 11 July 1981. impractical, NMR imagers based on 16. Crooks L, Arakawa M, Hoenninger resistive magnets will find a J, et al: Nuclear Magnetic Resonance clinical niche. Whole Body Imager Operating at 3.5 KGauss. Radiology 143:169-174, 1982. Vol. 5, No. 3A 175 METAL-NITROXYL INTERACTIONS. 34. V(IV), Fe(III), Co(II), Ni(II), AND Ag(II) COMPLEXES. j. ^ S. S. Eatonr, L. Fielding, K. M. More, R. Damoder, and G. R. Eaton Departments of Chemistry, ^University of Colorado at Denver, Denver, CO 80202 and *University of Denver, Denver, CO 80208 and Ni(II). I. INTRODUCTION II. SLOWLY RELAXING METALS EPR of intrinsic paramagnetic species and/or paramagnetic spin Using metals with long enough labels and spin probes added to bio- relaxation times that their EPR spec- logical systems is being used to tra can be observed at room tempera- determine the nature of species, their ture, we have explored the pathway for spatial relationships, and their rela- the metal-nitroxyl interactions. The tive motion (1). The task of under- synthesis of selected series of com- standing these EPR spectra and inter- plexes of these metals has been cru- preting the spectra to provide mean- cial to demonstrating the importance ingful descriptions of biological of both exchange and dipolar interac- function and malfunction is a compli- tions. These complexes have been stu- cated one. This is especially true in died in fluid solution, where the the various dual probe experiments in exchange interaction, J, gives rise to which two paramagnetic centers AB quartets (18) , in frozen solution, interact. where the sign of J can be determined Our goal is to obtain metrical if the exchange and dipolar contribu- information from the EPR spectra of tions are similar in magnitude (6,19), interacting spin systems in biological and in doped single crystals, where molecules. Our initial studies involve spectra as a function of crystal complexes of paramagnetic metals with orientation in the magnetic field per- ligands containing nitroxyl free radi- mit the separation of exchange and cals. These complexes have two dipolar contributions (8,15,20). It attractive features: they can be is . important to recognize that characterized by the usual methods, so exchange interactions which heretofore the spin interaction studies can be might have been considered negligibly performed on known species, and they small can be the dominant influence on exhibit interaction energies in the the EPR spectrum. range applicable to biological sys- The magnitudes of the exchange tems. interaction are interpretable in terms We have studied complexes of of the molecular orbitals. For exam- paramagnetic V(IV) (2-4), Mn(II) (5), ple, in a study of the copper Fe(III), Co(II) (6), Ni(II) (7), bis(hexafluoroacetylacetonate) and Cu(II) (3,4,8-14), and Ag(II) (2,15). vanadyl bis(hexafluoroacetylaceto- In addition we have examined collision nate) adducts of spin-labeled pyri- interactions between nitroxyl radicals dines it was observed that spin delo- and many paramagnetic transition calization from the metal into the metals and lanthanides (16,17). In pyridine orbitals was dominated by o- this report we summarize some of our pathways for Cu(II) but it-pathways recent results for slowly relaxing were also important for the vanadyl metal ions and present preliminary complexes (3,4). In the same series results on some complexes of the of complexes it was also observed that rapidly relaxing metal ions Fe(III) interactions through ester, amide, and 176 Bulletin of Magnetic Resonance Schiff base linkages between the pyri- dine and nitroxyl rings appeared to III. Fe(III) AND Ni(II) COMPLEXES correlate with the extent of n- bonding. When the same series of A spin-labeled Fe(III) tetraaryl ligands was coordinated to a porphyrin I was prepared with spin- cobalt(II) porphyrin, the spin- labeled side chain R^ attached to the delocalization was similar to that ortho position of one phenyl ring and observed for the related copper(II) para methyl groups on the other three complexes (6). Thus when the orbital phenyl rings. An analogous complex II interactions are similar the trends containing R2 instead of Rj was also observed for one metal can be used to predict spin-spin interactions for R i - -ir- R2 C-t another metal. In another series of o complexes a metal porphyrin was spin labeled with cis and trans acrylamide examined. The frozen solution EPR linkages and the analogous reduced (- spectra of the bis imidazole (Im) com- CH2CH2-) linkage (13) . The similarity plexes of I and II are shown in Figure in values of J for these compounds IB and 1A, respectively. The spectrum indicated that a-pathways dominated of II coordinated to imidazole (Fig. the spin-spin interaction. In some 1A) is characteristic of low spin other compounds evidence was obtained Fe(III) (S=l/2) porphyrins (23). The for an interaction pathway due to turning points in the spectrum of the orbital overlaps other than along the imidazole complex of I (Fig. IB) occur heavy atom framework of the molecule at magnetic fields which are averages (10,12). Some exchange pathways may of those expected for low spin Fe(III) be shorter than might be assumed. and for a nitroxyl radical. The The detailed information available averaging of g values occurs when the from rotated doped single crystal EPR spin-spin exchange is large relative studies of spin-labeled metal com- to the differences between the g and A plexes demonstrated that small confor- values for the two electrons. The mational changes can change the magni- off-scale peak in the center of the tude and even the sign of J (8,15,20). spectrum is due to a few percent of The combined data for VO(IV), Cu(II), the spin label concentration which is and Ag(II) complexes of spin-labeled not interacting with low spin Fe(III). porphyrins doped into Zn(TPP)(THF) When N-methyl-imidazole (Me-Im) was indicate that trends observed in fluid coordinated to I the spectrum shown in solution can be applied validly to Figure 1C was obtained. The spectrum similar systems in rigid matrices pro- is a superposition of a typical low vided that the molecular geometry is spin Fe(III) spectrum similar to that kept approximately constant. shown in Figure 1A and a broadened Resolved spin-spin splittings have nitroxyl signal. Thus the change in been observed for metal—nitroxyl dis- axial ligand from imidazole to methyl tances as long as 15 A in single cry- imidazole resulted in a dramatic stals and in fluid solution. In decrease in the magnitude of the -favorable cases a combination of fluid electron-electron exchange interac- solution, frozen solution, and single tion. In fluid solution the EPR spec- crystal EPR data interpreted in terms trum of the nitroxyl lines is of orbital interactions and dipolar broadened to a greater extent when I interactions provide a detailed pic- is coordinated to imidazole than to N- ture of the spin—spin interactions in methyl-imidazole. Additional ligands a molecule. The relative intensity of are currently under investigation to the half-field and g=2 transitions elucidate the factors which determine yields the distance between two S=l/2 the spin-spin interaction. centers (21,22), When spin-labeled ligand III coor- Vol. 5, No. 3A 177 dinated to nickel bis(ethylxanthate) integrated intensities of the two sig- the room temperature EPR spectrum of nals are equal. the nitroxyl lines was broadened by The metal ions Ni(II) and Fe(III) in the complexes reported in this paper have much shorter relaxation times than are observed for VO(IV), Cu(II), or Ag(II) complexes. For the Fe(III) the spin—spin interaction. When the complexes and the previously reported solution was frozen the spectrum shown Co(II) complexes (6) the metal EPR in Figure 2 was obtained. The spectrum can be observed in frozen nitroxyl lines were broadened by the solution (ca. 80-90 K) but not at room interaction with the nickel such that temperature. The interpretation of the amplitude of the signal was about the frozen solution Co(II) or Fe(III)- one tenth of that observed for 4-oxo- nitroxyl EPR spectra parallel our pre- 2,2,6,6-tetramethylpiperidin-1-yl vious results for other metals (e.g. (tempone) at the same concentration AB quartets for the Co(II)-nitroxyl (dotted line in Figure 2) although the spectra, strong exchange for the bis imidazole complex of I.) For several Ni(II) complexes with Ni(II) - nitroxyl distances of 6-10 A the effect of the nickel was to broaden the room temperature nitroxyl EPR spectrum beyond detectability (7). The Ni(II) complex reported in this paper has a Ni(II)-nitroxyl distance of 10-11 A (estimated from CPK molecu- lar models), but a much weaker spin- spin interaction. We speculate that the decreased spin-spin interaction is due to the additional —CH2- groups in the nickel-nitroxyl linkage. Figure 2. X-band EPR spectra of Figure 1. X-band EPR spectra of frozen solutions at -180 °C. ( ) frozen solutions at -180 lJC. A. Nickel bis(ethylxanthate)«III. ( ) 2 2 I«(Me-Im)2. Tempone plotted with one tenth the The iron impurity signal in the quartz amplification used for the nickel- is marked with an X. nitroxyl complex. 178 Bulletin of Magnetic Resonance The relaxation time of the nitroxyl 11. B. M. Sawant, G. A. Braden, R. E. is decreased by interaction with the Smith, G. R. Eaton, and S. S. metal. If the metal relaxation time Eaton, Inorg. Chem. 20, 3359 is short enough the nitroxyl spectrum (1981). can be broadened to the point of being 12. K. M. More, B. M. Sawant, G. R. essentially unobservable. This can Eaton, and S. S. Eaton, Inorg. occur both upon collision between Chem. 20, 3354 (1981). metal complexes (e.g. Cr tris(oxa- 13. K. M. More, G. R. Eaton, and S. late) ) and nitroxyl radicals in S. Eaton, Can. J. Chem. 25, 1392 solution, and in discrete complexes of (1982). metals (e.g. Fe(III), Ni(II)) with 14. K. M. More, G. R. Eaton, and S. ligands containing nitroxyl radicals. S. Eaton, Inorg. Chem. 22, 934 (1983) . IV. ACKNOWLEDGMENT 15. R. Damoder, K. M. More, G. R. Eaton, and S. S. Eaton, submitted This research has been supported in for publication. part by NIH GM21156, GM26566, and the 16. T. D. Yager, G. R. Eaton, and S. Petroleum Research Foundation, admin- S. Eaton, Inorg. Chem. 18, 725 istered by the American Chemical (1979). Society. 17. T. D. Yager, C. Benner, D. Dalai, R. Damoder, S. S. Eaton, and G. V. REFERENCES R. Eaton, unpublished results. 18. S. S. Eaton, D. L. DuBois, and G. 1. S. S. Eaton and G. R. Eaton, R. Eaton, J. Mag. Res. 32, 251 Coord. Chem. Rev. 26, 207 (1978). (1978). 2. K. M. More, S. S. Eaton, and G. 19. S. S. Eaton, K. M. More, B. M. R. Eaton, J.Amer. Chem. Soc. 103, Sawant, P. M. Boymel, and G. R. 1087 (1981) . Eaton J. Mag. Res., in press. 3. B. M. Sawant, A. L. W. S. 20. R. Damoder, K. M. More, G. R. Shroyer, G. R. Eaton, and S. S. Eaton, and S. S. Eaton, Inorg. Eaton, Inorg. Chem. 21, 1093 Chem., accepted for publication. (1982). 21. S. S. Eaton and G. R. Eaton, J. 4. J. K. More, K. M. More, G. R. Amer. Chem. Soc. 104, 5002 Eaton, and S. S. Eaton, Inorg. (1982). Chem. 21, 2455 (1982). 22. S. S. Eaton, K. M. More, B. M. 5. J. K. More, G. R. Eaton, and S. Sawant, G. R. Eaton, submitted S. Eaton, to be published. for publication. 6. S. S. Eaton, P. M. Boymel, B. M. 23. W. C. Lin in 'The Porphyrins', D. Sawant, J. K. More, G. R. Eaton, Dolphin, ed., vol 4, Academic submitted for publication. Press, N. Y. , 1979, p. 313. 7. S. Hafid, G. R. Eaton, and S. S. Eaton, J. Mag. Res. 51, 470 (1983). 8. R. Damoder, K. M. More, G. R. Eaton, and S. S. Eaton, J. Amer. Chem. Soc. in press. 9. D. P. Dalai, S. S. Eaton, and G. R. Eaton, J. Mag. Res. 42, 277 (1981). 10. K. M. More, S. S. Eaton, and G. R. Eaton, Inorg. Chem. 20, 2614 (1981). Vol. 5, No. 3A 179 Spin Label Oxirnetry: Measurement of Oxygen Concentration in Biological Samples James S. Hyde , W. K. Subczynski , W. Froncisz **, and C.-S. Lai.* *National Biomedical ESR Center, Dept. of Radiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 U.S.A. **On leave from Dept. of Biophysics, Jagiellonian University, Krakow, 31-120 Poland I. INTRODUCTION coincidence of spin-label T7 'S and lZ 's with a) for air saturated water In a series of papers (1-5), we have gives these spin-label oximetric meth- investigated ways in which bimolecular ods good sensitivity. collisions of molecular oxygen with ni- There are several types of experi- troxide radical spin-labels can be used ments that can be designed based on the to monitor oxygen concentration, diffu- Smoluchowski equation: Using water sol- sion, and consumption. Interpretation uble spin-label probes, very good tem- of results in these papers is based on poral resolution of the rate of change the Smoluchowski equation [O2] can be obtained during chemical reactions or cellular respiration. Since measurements of oxygen concentra- tion in water are available at a high This equation was originally derived by level of precision (8), and values of an application of Fick's second law in 0(02) in water are also known (9), a model where two solutes, in this case calibration of rate measurements is spin-labels and oxygen, were dissolved straightforward (1). in a continuum solvent. Here R is an Knowing [O2] in a solvent other than interaction distance for a collision water, perhaps by the partition tech- and p is the probability that a spec- nique of Subczynski and Hyde (5), mea- troscopically observable event occurs surements of D(02) can be made readily. when a collision occurs. It is assumed The experimental literature on diffu- that diffusion of the spin-label is sion of dissolved oxygen in liquids is negligible. This equation does not very sparse, and our methods may be contain the spin-label concentration; generally useful in a wide range of it predicts how frequently a given systems. Our literature search reveal- spin-label will collide with oxygen ed that no measurements of oxygen dif- molecules. fusion have been made by any technique Heisenberg exchange between spin- on long chain hydrocarbons, for exam- labels and oxygen results in a broaden- ple. ing of ESR spin-label lines. This T2 In heterogeneous systems such as method was introduced by Backer et al. membranes or cells, the local product (6) and used by Windrem and PI achy (7) D(02)[02] can be determined at any site and ourselves (1). Moreover, Heisen- that can be spin-labeled using the J\ berg exchange between a fast relaxer method. This product is itself of in- (oxygen) and a slow relaxing species terest. (spin-label) provides thermal contact In this paper we summarize some ini- of the slow relaxer to the lattice, tial results of several methodological thereby altering J\ of the spin-label. projects in the field of spin-label This 1\ method was introduced by Sub- oximetry for which longer papers will czynski and Hyde (3). The fortuitous eventually appear. 180 Bulletin of Magnetic Resonance II. On the validity of the Smolu- tion. Oxygen diffuses about as readily chowski equation. as in water even though the macroscopic We have compared values of D(02) in viscosity is 100 times greater. water obtained using the Smoluchowski equation with the compendium of values IV. Oxygen broadening of CTPO spin- assembled by St.-Denis and Fell (9) label. that are based on macroscopic diffusion The spin label CTPO of O2 against a concentration gradient. We find, as did they, that the Stokes- Einstein equation is satisfied: CH- CH, CH^ N Chh I- D « T/TI 0 is particularly useful as an oximetric with constants of proportionality of probe in biological samples because it 10 2 practically does not partition into K = 6.92 x 10" gm cm/sec (9) membranes (1). In the absence of oxy- 10 2 gen, the superhyperfine coupling to K = 8.84 x 10" gm cm/sec (this protons is dominated by 12 equivalent work). methyl protons and one ring proton. Couplings to the amide nitrogen and 1 Windrem and. PI achy s interaction dis- other protons are negligible, \lery tance of 4.5A was used and p = 1. This good agreement is possible between sim- remarkable agreement leads strong sup- ulations and experiments. The ring port to the following conclusions: proton coupling varies from 0.54 to (a) The exchange integral between 0.46G between 10 and 80°C, while the spin-label and O2 is sufficiently methyl coupling changes little with strong to result in a measurable event temperature. This temperature depen- on every collision even though the dence is presumably due to some intra- transl ational correlation time is as molecular motional mode. At a temper- short as 10-Hs. Since the method ature of 50°, there is an accidental works so well in water with its low degeneracy of a factor of 2.5 between viscosity, it is almost certain to work ring and methyl proton couplings, and in higher viscosity solvents. the number of proton superhyperfine (b) The interaction distance of lines changes from even (below 50°) to 4.5A seems to be a property of spin odd (above 50°). Simulations of spec- label and O2 and not of the solvent. tra obtained in the presence of oxygen varying only the linewidth, which is III. Diffusion of oxygen in mixed lorentzian, are in excellent agreement long-chain hydrocarbons. with experiment, yielding precise nu- In light paraffin oil (PX44-07, merical values for the bimolecular col- Matheson, Coleman and Bell) we find lision rate. that IV. Limiting sensitivity for spin- 0 62 D « (T/n) - , label oximetry. Lai et al. (1) using the spin-label a type of dependence also recently re- T2 method obtained a limiting sensiti- ported by Evans et al. (10,11) when the vity for detection of dissolved molecu- solvent molecule is much larger than lar oxygen of about luM. This value is the solute molecule. Assuming a con- close to reported values for the centration for dissolved oxygen in par- Menten-Michaelis constant KM for affin oil at 15°C of 5.0mM (12) for 1 cellular respiration. These authors atm. 0?, a value for D of 0.8 x were interested in measuring KJS/J over a lO'^cmvs was obtained which is about range of conditions and a search was two orders of magnitude greater than therefore initiated for an experimental predicted by the Stokes-Einstein equa- approach that would improve the sensi- Vol. 5, No. 3A 181 tivity by, hopefully, an order of mag- 7. Windrem, 0. A., and W. Z. Plachy, nitude. Biochim. Biophys. Acta. 600:655 A way has been found to achieve this (1980). objective using the loop-gap resonator (13) tuned to the dispersion mode (14) 8. Hitchman, M. L. 1978. Measurement under saturating conditions using 100 of Dissolved Oxygen. John Wiley & kHz field modulation with the amplitude Sons, Inc., New York. about equal to that of the envelope of the proton superhyperfine lines of the 9. St.-Denis, C. E., and C. J. D. spin label. Under these conditions the Fell, Can. J. Chem. Eng. 49:885 phase of the detected signal depends on (1971). the spin-label J\ (15,16). Since T]_ has been shown to depend on the bimolecular 10. Evans, D. F., T. Tominaga, and C. collision rate, precise phase measure- Chan, J. Solution Chem. ^:461 ments become useful for oximetric stud- (1979). ies. We have achieved a limiting sen- sitivity of O.lpM using only luL of 11. Evans, D. F., T. Tominaga, and H. sample. T. Davis, J.Chem. Phys. 74:1298 (1981). ~~ Acknowledgments 12. Handbook of Chemistry and Physics, This work was supported by grants 47th Edition, Chemical Rubber Co., GM22923, GM27665 and RR01008 from the Cleveland. National Institutes of Health and Grant PCM 8118976 from the National Science 13. Froncisz, W., and J. S. Hyde. J. Foundation. Magn. Reson. 47, 515-521 (1982). 14. Hyde, J. S., W. Froncisz, and A. Kusumi, Rev. Sci. Instrum. 53, References 1934-1937 (1982). 1. Lai, C.-S., L. E. Hopwood, J. S. 15. Hyde, J. S., Phys. Rev. _U9, 1482 Hyde, and S. Lukiewicz, Proc. (1960). Natl. Acad. Sci. U.S.A. 79:1166 (1980). ~~ 16. Mailer, C, and C. P. S. Tayler, Biochim. Biophys. Acta ^322, 195 2. Popp, C. A., and J. S. Hyde, J. (1973). Magn. Reson. 43:249 (1981). 3. Subczynski, W. K., and J. S. Hyde, Biochim. Biophys. Acta. 643:283 (1981). 4. Kusumi, A., W. K. Subczynski, and 0. S. Hyde, Proc. Natl. Acad. Sci. U.S.A. 29:1854 (1981). 5. Subczynski, W. K., and J. S. Hyde. Biophys. J. 41:283 (1983). 6. Backer, J. M., V. G. Budker, S. I. Eremenko, and Yu. N. Molin, Bio- chim. Biophys. Acta. 460:152 (1977). 182 Bulletin of Magnetic Resonance SHORT COMMUNICATIONS AND POSTERS Vol. 5, No. 3/4 183 CP/MAS '3c NMR SPECTRAL EVIDENCE OF LONG-RANGE SUBSTITUENT EFFECTS IN RIGID OPIATES Charles Eric Brown", Sandra C. Roerig*, James M. Fujimoto* and Vern T. Burger* Medical College of Wisconsin, Milwaukee, WJ 53226 Veterans Administration Center, Wood, Wl 53193 Nicolet Analytical Instruments, Madison, Wl 53711-0508 Long-range substituent effects have been suggested to affect the recognition of chemically substituted morphine mol- ecules by the opiate receptor(s) in the central nervous system and thereby to affect their pharmacological activities. "3c NMR spectroscopy provides a direct assay for the differences in steric, inductive and intramolecular electric field effects that have been proposed to exist between the various opiates. Cross polarization and magic angle sample spinning are superior to high- resolution techniques because they provide improved sensitivity and permit direct comparison with crystallographic data. CP/MAS '3c NMR spectra of protonated 71 and non-protonated morphine in the solid state indicate that steric and intra- 4] () 1)2 molecular electric field effects permit 16) 115 interaction between the nitrogen and the 311 phenolic hydroxyl group on carbon-3. 200 150 100 SO 0 Similar interaction is not observed be- tween the nitrogen and the hydroxyl group on carbon-6. Figure 1. CP/MAS ^ 3c NMR spectrum of Ring D of morphine is not held in morphine-3~ethereal sulfate. The only one rigid conformation as commonly numbered lines indicate peaks that shift assumed. The substituent on the nitro- relative to morphine sulfate. gen affects the chemical shifts of carbons-9, 15 and 16 of ring D and of acetyl-morphine, in which the chemical carbons in rings A and C. Methyl, ethyl shifts of carbons-15 and 16 are and sulfate groups in ether linkage at unaffected by substitution, exhibit carbon-3 also shift the resonances of greater analgesic potency than morphine. rings A, C and D, whereas an acetyl Thus, changing the conformation of ring ester at carbon-3 shifts only the D in these substituted opiates from that resonances of rings A and C. Sulfate of morphine is associated with reduced ether and acetyl ester groups at carbon- analgesic potency. (Supported by NIDA 6 also do not appear to alter the con- grant DA00A51 and VA grant 03P.) formation of the D ring. Substituents on the nitrogen'or carbon-3 that were found to change the chemical shifts of carbons-15 and 16 of ring D relative to those of morphine also reduce the analgesic potency below that of morphine. In sharp contrast, morphine-6-ethereal sulfate and 3,6-di- Bulletin of Magnetic Resonance DIPOLAR CORRELATION FUNCTIONS AND SPIN RELAXATION RATES FOR FINITE TWO-DIMENSIONAL SYSTEMS. J.-P. KORB* and H.M. McCONNELL3™ x C.M.O.A. du C.N.R.S. 23, rue du Maroc, 75019 Paris, France, xs Stauffer Laboratory for Physical Chemistry, Stanford University, Stanford, California 94305, U.S.A. Magnetic resonance is very useful for found, in both surfaces, even at fre- obtaining dynamical information on two- quencies close to zero, in opposition or quasi two-dimensional (2D) systems to the logarithmic divergences of these whether for adsorb tion of mono-or poly- rates for infinite surfaces. From the atomic fluids upon solid surfaces,motion theoretical variations of these rates of intercalated complexes between laye- with the lateral diffusion coefficient red metals or lateral diffusion in model one shows a diminution of the minimum of and natural biological membranes.However T. compared to those obtained in the same there are always some problems in the conditions for 3D systems and an impor- theoretical interpretation of lineshapes tant shortening of T~ which stays always and spin-relaxation rates for these low- shorter than T even in the extreme dimensional systems. For instance, the narrowing case. (3). These results are in seemingly paradoxical logarithmic diver- good agreement with nuclear magnetic gences of the spectral densities and resonance experiments of polyatomic consequently of the spin-relaxation rates fluids physisorbed on quasi-spherical at (xi ->• 0 which appear from application beads (4). For the planar surfaces imp- of the well known theory of Kubo (1) to ortant anisotropies are found in the va- the case of unbound 2D diffusive motion riations of these rates with the angle of spins in infinite systems. between the constant magnetic field B~ Theoretical attempts have been made and the normal, in conformity with exper- to eliminate these model-dependent diver- iments on 2D diffusion of intercalation gences. For instance, the consideration complexes (5). of rapid spin-lattice relaxation process, Our theoretical results (2,3) can be not explicitly dependent on 2D diffusion, very useful for those who are interested which provides a natural cuttoff of the in how magnetic resonance might be emp- long-time decay of the pairwise correla- loyed to study restricted motion in 2D tion function. This is naturally an ad homogeneous surfaces or for spin labels hoc procedure which has to be checked embedded in biologocal membranes. seriously a posteriori. We have shown previously (2) that the effects of bound 1. R. KUBO and K. TOMITA, J. Phys. Soc. diffusion on translational motion, in a (Jpn.) _9> 888 (1954). restricted planar surface, enhanced the 2. J.-P. KORB, D.C. TORNEY and H.M. time-decay of the secular dipolar corre- McCONNELL, J. Chem. Phys. 78_, 5782 lation function and led to a finite value (1983). of the corresponding spectral density 3. J.-P. KORB and H.M. McCONNELL, submi- even at zero frequency. tted to J. Chem. Phys. Here we apply the Kubo's theory in 4. J. TABONY, Progr. in NMR Spectr. \h_, the fast motion regime to investigate the 1 (1980). relaxation behavior cif spins in dipolar 5. A. AVOGADRO and M. VILLA, J. Chem. interactions diffusing in finite planar Phys. 66, 2359 (1977). and spherical 2D surfaces. Convergent expressions of the spin-spin !„" and spin'-'..lattice T ' relaxation rates are Vol. 5, No. 3/4 185 ZERO-FIELD RESONANCE SPECTROSCOPY S.J. Strach and R. Bramley Research School of Chemistry, Australian National University, G.P.O. Box 4, Canberra, A.C.T. 2601, Australia EPR only rarely requires an external In more complex situations ZFR may static magnetic field for its detection. separate out some of the paramagnetic The only requirement is the existence of species present whose EPR spectra a splitting of states within which elec- might be entangled. tron spin magnetic dipole transitions Powder and amorphous materials lend are allowed. Frequently the parameters themselves to ZFR studies since the of the spin Hamiltonian of interest are orientation of a paramagnetic species not the Zeeman terms which require a does not affect the ZFR frequencies, magnetic field for determination but the only the intensity. This is because fine, hyperfine and nuclear quadrupole there is no field competing for the structure terms which split the spin quantization of the spin. Further states in zero field and allow detection advantages can be gained because many of zero-field EPR (ZFR). The technique transition metal complexes have ZFR has recently been reviewed (1). In ZFR spectra in the low microwave frequency the frequency is swept. The technique region where dielectric loss problems benefits by removal of several error are less severe. Aqueous solution sources. These include errors of field can be more readily studied for similar measurement and angular orientation of reasons. crystals, errors associated with powder Finally complementarity of EPR and spectra analyses, wrong assignments in ZFR is stressed. This occurs cases of magnetic inequivalence and particularly with swept-frequency EPR multiple sites, and errors due to the in the presence of a magnetic field. assumption of parallelism of g with Terms in the Hamiltonian can lead to other tensor principal axes. observable level anti-crossings and We have analyzed the ZFR of Mn2+ in the interactions responsible for several salts and found considerable these are best studied in the field and parameter deviation from literature EPR frequency regions containing the anti- values and improved accuracy. For crossings by frequency sweeping example, ZFR analysis of Mn2+ in the techniques. Tutton salt ZnK2(S0if)2.6H20 gave fine- structure parameters b£ = -1067+1, (1) R. Bramley and S.J. Strach, b\ = 514±3, b°h = 14±1 MHz compared with Chem. Rev. 83, 49 (1983). a previous EPR analysis with b\ = -1044±8 b\ = 420±84, b°h = 15±1 MHz. The simplicity of ZFR of 1=0 isotopic materials can be advantageous. 3+ For Cr in La2Mg3(N03)12.24H20 the EPR transitions for the Cr3+ sites and Mn2+ impurity are centred around the field for g=2. The ZFR, however, completely separates out the three species, with the Cr3+ spectrum consisting of just one line for each site. 186 Bulletin of Magnetic Resonance EPR IN PULSED MAGNETIC FIELDS P. de Groot, P. Janssen, F. Herlach, G. De Vos and J. Witters Department of Physics, University of Leuven, Belgium We have developed an EPR spectrometer a function of temperature for which we with pulsed magnetic fields (up to 40 can offer no explanation. Tesla, pulse duration 10 ms.) and far Ferromagnetic resonance in Ni films de- infrared laser sources. Several high posited by evaporation on polyethylene intensity EPR signals have been studied foils give resonance lines as shown in with it,generally in a transmission mo- fig. 2. de. Using Maxwell's equations and Bloch's equation of motion for the mag- netization, a simple analytical solution for the transmission spectra was ob- tained and could be fitted very well to the experimental results, including the complete reflection in the region where the permeability becomes negative and the interference patterns for the multi- ple reflections within the sample. Measurements on Li - rare earth - F4 , as shown in fig. 1 for LiErF4, show tran- sitions in reasonable agreement with the Fig. 2. Ferromagnetic resonance at 337ym level structures that one can find in in a thin (±1000 A) Nickel film. the literature, but displaying unex- plained shifts at the highest frequen- The g-factor was 2.19 , in good agreement cies. with usual microwave values. The line- width was about 5 T , which is much broa- der than what one would expect from ex- trapolation of microwave data. The ex- tra linewidth could possibly be caused by unresolved spin wave spectra, but this will have to be investigated in samples on different substrates. BIT) Fig. 1. Pulsed field resonance at 337um (HCN laser) in LiErF4. Measurements in (CH3 >4 NMnCl3 (TMMC), show a strong resonance line due to Mn'2* ions in the linear chains and another one due to ions in broken fragments. The main resonance showed a temperature dependence, with a maximum of 0.6 T at about 4 K, which can tentatively be ex- plained by thermal excitation of soli- tons. This line shows also a g-shift as Vol. 5, No. 3A 187 NUCLEAR QUADRUPOLE PROBES OF PARAMAGNETIC MOLECULES USING ELECTRON SPIN ECHOES. M.K. Bowman, A. Kostka and J.R. Norris Chemistry Division, Argonne National Laboratory, Argonne, IL 60439 In solids, the electron nuclear actions, chemical bonding information hyperfine and nuclear quadrupole is obtained about the nitrogen in couplings can interact to destroy all these molecules (Table II). We find the selection rules for nuclear spin transitions. This phenomenon results Table II in extra transitions in EPR spectra Molecule #Pi Electrons and in envelope modulation (ESEEM) in electron spin echo spectroscopy. The Chlorophyll at 1.30 echo envelope is modulated at the Bacteriochlorophyll at 1.23 eigenfrequencies of the nuclei with (Bacteriochlorophyll a) . 1.28 intensities which are determined by Mg pthalocyanine^ 1.52 products of the nuclear eigen- Cu tetraphenylporphyrin^ 1.50 vectors. To completely analyze this Ag tetraphenylporphyrin*5 1.46 modulation requires the solution of the general eigenvalue-eigenvector that the chlorophyll and bacterio- problem with hyperfine, quadrupole and chlorophyll radical cations show much Zeeman interactions for all orienta- less pi electron density at the tions of the center present in the nitrogens than do other neutral sample. This has all but prevented metalloporphyrins. Indeed, the dif- the use of ESE for determining ferences between the in vitro radical hyperfine and quadrupole interactions cation of bacteriochlorophyll a and in powder samples for nuclei like the in vivo radical cation of a bac- nitrogen with large quadrupole inter- teriochlorophyll a dimer in the actions. photosynthetic bacteria R. rubrum indicate less pi electron density in We have obtained an analytical the monomer cation than in the dimer form for the modulation for 1=1 with cation as one would expect. no restrictions on the hyperfine, quadrupole or Zeeman interactions. We The ESE technique appears to be a have used this solution to simulate good method for obtaining quadrupole the modulation from a number of para- couplings from 14N in paramagnetic magnetic molecules containing nitrogen molecules when the 14N hyperfine is and have obtained the quadrupole comparable to the nuclear Zeeman tensors and the hyperfine tensors. interaction (1MHz near 3300 G.). The These quadrupole parameters are nitrogen quadrupole couplings are a contained in Table I. good probe of the chemical bonding in paramagnetic molecules. Table I £ REFERENCES Radical |K| 1S.A. Dikanov, Yu.D. Tsvetkov, M.K. N-coppingers .60 .65 Bowman and A.V. Astashkin, Chem. Phys. Chlorophyll at .70 .57 Lett. 90_ (1982) 149. Bacteriochlorophylit .68 .71 (Bacteriochlorophyll) t .65 .65 20. Lumpkin, J. Chem. Phys. 62 (1975) in R. rubrum 3281. 'in MHz. 3T.G. Brown and B.M. Hoffman, Mol. When the Townes Dai ley analysis Phys. 39 (1980) 1073. i s appl i ed tothese quadrupole inter- 188 Bulletin of Magnetic Resonance CARBON-13 NMR STUDIES OF SOLID FORMATES AND ACETATES Christopher J. Groombridge, Robin K. Harris* and Kenneth J. Packer School of Chemical Sciences, University of East Anglia Norwich, England NRlj- 7TJ A series of metal formates and Ca(0Ac)2. 187-6, 186.3, acetates (with cations Na, K, Mg, Ca, Sr, Ba, Zn, Cd, Hg and Pb) were studied by 182.0, 178.3 ppm. solid-state 22.6 MHz carbon-13 NMR in a Ba(0Ac),.H,0 183.6, I82.lt, number of ways. Several of the compounds were examined in differently-hydrated 181.9, 179.8 ppm. forms. In all cases 13C-{1H} cross- polarization methods were used, together For the latter compound single-crystal with high-power proton-decoupling during X-ray work confirms the existence of signal detection. four non-equivalent sites. This is also found for strontium acetate hemihydrate, Shielding anisotropies were measured and the NMR data are consistent with for some of the compounds by bandshape- this fact. Single crystals of the fitting of static spectra and by analysis calcium salt suitable for X-ray studies of spinning-sideband intensities under could not be obtained. MAR NMR also slow MAR conditions. The shielding provides a reliable alternative to X-ray tensor components for the carboxyl powder diffraction for recognition of resonances were found to be in the different solid modifications. following ranges (relative to the Calcium acetate hemihydrate proved to shielding in tetramethyl silane): be a useful compound for checking spectrometer performance (both S/N and o —2il+ to -237 ppm xl resolution) in the CP/MAR mode. The to spectrum of the carbonyl region is ~ ppm shown in the following figure. to ~ However, there were considerable variations from compound to compound, depending on the environment in the crystal structure. In fitting the static spectra, a Gaussian broadening function was necessary which ranged in width (at half-height) from 320 to 600 Hz. Rapid MAR showed splittings in the carbonyl and (for the acetates) methyl regions of the spectra for many of the compounds, indicating the existence of non-equivalent anions in the unit cell- In the case of calcium acetate hemi- hydrate and barium acetate monohydrate four distinct signals are seen in the carbonyl region under rapid MAR con- ditions at the following chemical shifts (calculated from the signal of tetramethylsilane): Vol. 5, No. 189 RELATIONSHIPS BETWEEN CARBON-13 CHEMICAL SHIFTS AND CONFORMATIONS OF OLIGOSACCHARIDES AND CELLULOSE IN THE SOLID STATE F. Horii, A. Hirai, and R. Kitamaru Institute for Chemical Research, Kyoto University Uji, Kyoto 611, Japan Isotropic chemical shifts of solid j^ was 69.4 kHz and the rate of MAS organic compounds obtained by CP/DD/MAS was about 3.2 kHz. 13c NMR spectroscopy will be primarily Figure 1 shows a linear relationship related to the conformations of con- between the chemical shifts of the CH2OH cerned carbons as long as subsidiary carbons of different oligosaccharides effects such as packing and hydrogen and the torsion angles X about the exo- bonding are not significant and no rapid cyclic C-C bonds which were determined transition occurs among allowed con- by x-ray analyses. Their chemical formers . In this paper we report pro- shifts fall into three groups of 60-62, nounced relationships between l^C 62.5-64.5, and 65.5-66.5 ppm, which are chemical shifts and torsion angles for related to the gauche-gauches gauahe- exo-cyclic C-C bonds and (3-1,4-glycosidic tvans, and trans-gauche conformations, bonds of oligosaccharides and cellulose. respectively. In Figure 2, the chemical 25 MHz CP/DD/MAS 13C NMR spectra were shifts of Cl and C4 carbons are plotted obtained with a JEOL JNM FX-100 spectro- against torsion angles 0 120 240 360 X /degree -60 -40 -20 0 20 40 60 Figure 1 13C chemical shifts of the Cl^OH carbons vs. torsion angles X. W or 0/degree a: a-D-glucose, b: 3-D-glucose, Figure 2 Chemical shifts of the C4 and Cl carbons c: B-D-cellobiose, d: a-D-lactose-H20 vs. dihedral angles ij>, <£. a: 6-cellobiose, b: 6-methyl cellobioside-CI^OH, e: sucrose, f: a-melibiose.H20, g: 3-methyl cellobioside-Ct^OH, c: a-lactose monohydrate, d: 8-lactose, h: raffinose-5H20; e: cellulose I(Blackwell), f: cellulose I(Sarko), g: cellulose II(Blackwell), h: cellulose Il(Sarko), O » • : a- and 3-glucopyranoses. A ,A : a- and 8-galactopyranoses. i: cellobiose in solution X 5 8-fructofuranose3. 190 Bulletin of Magnetic Resonance SAMPLE LOCALIZATION USING SURFACE COILS AND MULTIPULSE SEQUENCES FOR HIGH RESOLUTION NMR M. Robin Bendall School of Science, Griffith University, Nathan, Qld 4111, Australia. An rf pulse applied with a surface broad signals generated by the field coil excites a fairly undefined sample profiling. region because of the complete inhomo- For various reasons, not least the geneity of the B field. Recently it has ease of use, it is preferable, to elim- been shown [1] that pulse sequences, inate the need for field gradients of dubbed 'depth pulses', of the form: any sort and this can be achieved by 28;8[±x];(2e[±x,±y])n acquire signal, using a double surface coil. Thus it is where 26 is a pulse twice as long as a 6 possible to use a large irradiation coil, pulse, n is an integer, and [±x] and and a smaller coaxial detection coil [±x,±y] signify independent phase cycl- which discriminates on the basis of sen- ing of these pulses between individual sitivity against the shallow signals at transients with suitable alternation of large off-axis distances. This somewhat receiver phase. Signals are markedly re- crude arrangement has also been proved duced from regions where 0 differs sig- by phantom sample studies. In theory at nificantly from IMT/2 (m an odd integer) . least, potentially the best method is to For example, for n=2, NMR signals are use a two coil system where some pulses reduced to <5% of maximum from regions are applied with one coil and some with except where 50 Vol. 5, No. 191 IN VIVO 31P NMR STUDIES ON EXPERIMENTAL CEREBRAL INFARCTION USING TOPICAL MAGNETIC RESONANCE (TMR) Hirakawa K*, Naruse S, Horikawa Y, Tanaka C, Higuchi T, Nishikawa H and Watari H Kyoto Prefectural University of Medicine. Department of Neurosurgery, Kamigyo-Ku, Kyoto._ Japan Sequential metabolic changes in the tabolism and EEG during the course of rat brain were measured by using topical cerebral ischemia and its recovery in magnetic resonance (TMR) of 31-phospho- the same experimental animals. It is rous during the course of cerebral is- conclueded that the phosphours compounds chemia and its recovery period, 31PNMR changes very rapid after induction of spectra were measured with a TMR-32 the ischemia and these changes recover- spectrometer (Oxford Research Systems, ed very rapidly after the restoration of England), operating at 32.5 MHz. Elec- circulation. EEG also changes rapidly troencepholography (EEG) was monitored after the ischemia, but its recovery concomit antly„ after the recirculation is much slower The experimental cerebral ischemia than that of the energy metabolism. was induced in rats with the four-vessel The measurement of 31P MR spectrum is ligation (l)o There were, in order of indispensable not only to investigate the high resonant frequency, several the in vivo energy metabolism in the peaks in the spectrum of the normal cerebral infarction but also to asses brain: the S-ATP, a-ATP and a-ADP with the convalescent power of the damaged contribution from NAD+/NADH, Y-ATP, and brain both experimentally and clinical- 3-ADP, phosphocreatine (PCr), phospho- ly. diesters or 2a3 DPG, inorganic phosphate References, (l) Pulsinelli WA and with contribution from AMP (2)o EEG in Brierley JB: Stroke 10:267-272, 1979 the normal rat showed a-wave dominant (2) Naruse S, Takada S, Koizuka I and pattern. The bilateral coagulation of Watari H: Jpn J Physiol 33:19-28, 1983 the cerebral artery (preischemic period) did not show any changes in NMR spectrum and EEG (Fig a), but the subsequent bi- lateral ligation of internal carotid ar- teries (ischemic period) produced a de- crease in the peak of ATP and PCr and a concominant increase in the peak of Pi within a few minutes (Fig b). The chem- ical shift of increased peak of Pi be- came smaller than the normal one, indi- cating that the brain tissue became aci- dotico EEG became flat pattern during this period. As soon as the circulation was restored following the 30-minute pe- riod of the ischemia (recirculation pe- riod) , PCr and ATP recovered and Pi de- creased rapidly (Fig c)u At 30 minutes after the recirculation, 31P NMR spec- trum became identical with that of the preischemic state (Fig e). In contrast to the rapid recovery of energy metab- Olism after recirculation, EET did not show any recovery with 30-minute period after recirculation and its abnormality persisted for 12 horns (Fig f)o We thus demonstrated the changes of energy me- 192 Bulletin of Magnetic Resonance NEW RESULTS ON EPR STUDIES OF QUARTZ CRYSTALS Harish Bahadur and R. Parshad National Physical Laboratory- Hillside Road, New Delhi-110012. The present work reports new being accompanied by intense smoky results on a variety of quartz coloration (Fig.2). crystals, mainly non-optically clear and variously processed natural and synthetic quartz crystals. Some of the results are described below. Non-optically clear natural crystals 10 kOe (i) Gamma-irradiation Our work on frequency beha- Fig.2 EPR spectrtm3 showing sharp line viour of these types of crystals svperposed on a broad resonancet (H. Bahadur and R. Parshad, Phys. of a natural qvartz crystal upon stat. sol. (a) 67, 683-692, 1981) y-irradiation (Dose =7.5 MRads) led us to expect increased crystal recorded at room temperature. imperfections in them compared to optically clear crystals. The EPR (ii) Neutron-cum-gamma irradiation results confirm this. Apart from narrow EPR lines due to defects The crystals were neutron ir>^ being observable at room tempera- radiated (thus producing vacancies ture, there were also some very and dislocations) prior to irradia- broad lines (% A Hpp^l k Oe in tion. This gave the expected broad irradiated crystals centered EPR superposed with sharp g-**2 line. around g~2.5 (Fig.l). Additional- Associated was the increased smoky ly interesting was the fact that coloration. these broad lines had a limited +5° X-seed Ge doped synthetic crystal Different zones of the irra- diated crystal gave different EPR signals. One of the zones which colored most- upon Y-irradiation gave 10 kOe a very broad signal (of the type obtained for natural crystals) super- Fig.l EPR spectrwi, showing broad posed on which was a sharp line (all resonance* of a natural qvartz this indicating large concentration crystal vpon y'-irradiation of crystal defects), Additionally, (Dose = 7.5 MRads) recorded EPR spectrum characteristic of Ge at room temperature appeared (J.A. Weil, Jour. Chem. Phys 55, 4685-4695, 1971). Probably these life time (in most cases less two facts are correlated. than a month). The broad signals must be due to electron trapping AT-cut-seed grown crystal in- large enough dislocations The crystal was much colored (hence the large width), the upon irradiation but did not give limited life time resulting from any EPR at room temperature, the detrapping of electrons from the result signifying that there are dislocations due to low enough almost no defects, the coloration energy of activation. In some being only due to Al 3+ centers, cases, sharp lines were superposed the EPR for which is observable o on these very broad lines this only at low temperatures (~77 K) H. Bahadur is a Homi Bhabha Fellow Vol. 5. No. 3A 193 ANALYSIS OF NUCLEAR MODULATION AMPLITUDE IN ELECTRON SPIN ECHO SPECTROS- COPY. H. Barkhuijsen, R. de Beer and D. van Ormondt, Applied Physics Lab., THD, P.O. Box 5046, 2600 GA Delft, The Netherlands. Often the site of a paramagnetic cen- tre in a solid can be identified by mapping the positions of magnetic nu- clei surrounding it. The usual techni- que for this is Electron Nuclear Dou- ble Resonance (ENDOR). Notwithstanding its undisputed success, ENDOR has how- ever a drawback in that the signal in- tensity depends in a complicated way on relaxation processes. As informa- tion about relaxation is often not a- vailable it is difficult to interpret the intensity in terms of the number of participating nuclei. Since the in- troduction of Electron Spin Echo Enve- lope Modulation (ESEEM) spectroscopy . 58 . 60 . 62 (1) the interpretation of nuclear sig- nal intensities has substantially im- proved. This is because the ESEEM sig- nal arises without the help of relaxa- tion. The present work concerns a three- pulse ESEEM study of the F-centre in KC1. A single crystal was chosen be- cause it allows better observation of separate shells (2), According to a detailed quantitative analysis of the ESEEM signal of 39K, there are 25.4 ± 2 nuclei in shell V versus 24 in real- ity. This result was obtained by comp- aring simulated and experimental spec- tra. See fig.l. The simulation incor- porates differences of the decays of the various frequency components. In addition, the effect of other nuclei Figure 1. Experimental and simulated 39 on the modulation amplitude of a sin- (dotted line) spectrum of K in gle nucleus is taken into account us- shell V (B//[100]) obtained from Fou- ing known spin Hamiltonian parameters rier transformation of the time do- (2). main signal. Three different lengths of the latter were used in order to References. obtain proper decay constants for the (1) W.B. Mims, Phys.Rev. B5, 2409 simulation: 409.4, 819.0 and 1638.0 (1972). Ms, from top to bottom. The average (2) H. Barkhuijsen, R. de Beer, E.L. de ratio of experimental and simulated Wild and D. van Ormondt, J. Magn. peak heights in the figure is 1.06 i Reson. 50, 299(1982). 0.09. 194 Bulletin of Magnetic Resonance SPIN DIFFUSION AND LONG RANGE ORDERING IN A QUASI-TWO-DIMENSIONAL MAGNETIC SYSTEM: BIS [ 1,2-BIS(2-METHOXYETHOXY)ETHANE ] SODIUM BIPHENYLIDE (NaBp.2Tg). A TEMPERATURE DEPENDENT STUDY E. de Boer, R. Murugesan and M.C.M. Gribnau Research Institute of Materials, University of Nijmegen, The Netherlands In earlier publications (1,2) it has perpendicular to the magnetic plane (be been shown that spin diffusion effects plane), i.e. with BQ the magnetic field manifest itself very clearly in the ESR parallel to a*. This is caused by the spectra of the quasi-two-dimensional predominant influence of the secular magnetic system NaBp.2Tg (Bp=biphenyl, terms of the electronic dipolar interac- Tg=triglyme=CH3O(CH2CH2O)3CH3). In this tion, as a consequence of the long time study the influence of the temperature behavior of the spin correlations (spin on the angular behaviour of the line- diffusion). At 1.2 K the linewidth vari- width of the exchange narrowed ESR line ation is different, the largest line- and on the lineshape is investigated. In width is now measured with BQ in the mag- addition results of susceptibility mea- netic plane (BQIIC) . The lineshape at 1.2 surements are given. K is Lorentzian at all orientations, whereas at 77 and 295 K the lineshape de- viates markedly from Lorentzian by spin- diffusion effects (2). This behavior at 1.2 K is typical for 3-dimensional mag- netic systems. Apparently at 1.2 K long range order exists, brought about by in- terlayer (antiferromagnetic) exchange interaction. The susceptibility has been measured from 1.1. to 270 K. The high temperature points follow a Curie-Weiss law with a positive Weiss constant of 6.9 K, the low temperature points deviate from the Curie-Weiss line. In a plot of X versus T a broad maximum is found at about 2.4 K. One may conclude from this that at low temperature the spins in the magne- tic plane order antiferromagnetically, 1 - whereas at higher temperatures the fer- romagnetic coupling prevails. This can be reconciled by the presence of several 20 exchange mechanisms with different tem- perature dependencies (3). Fig. 1 illustrates the angular beha- (1) Takizawa, 0., Srinivasan, R., and de vior of the linewidth, measured at 9.4 Boer, E., Mol. Phys. 44, 677 (1981). GHz in the ac plane at 1.2, 77 and 295 K. (2) Murugesan, R., and de Boer, E., Chem. ABp =derivative peak-to-peak width). At Phys. Lett. 95, 301 (1983). 295 K and 77 K the angular variation of (3) Nagaev, E.L., Kovalenko, A.A., Solid the linewidth is determined by spin dif- State Commun. 38, 1121 (1981). fusion (1). The largest ABpp is measured Vol. 5, No. 3A 195 EPR STUDIES ON PAIRS OF JAHN-TELLER DISTORTED HEXAKIS-PYRIDINE-N-OXIDE COPPER(II), Cu(C,H NO)f, IONS DO c o E. de Boer, C.P. Keijzers, G. van Kalkeren and J.S. Wood Department of Molecular Spectroscopy, University of Nijmegen, The Netherlands The hexakis pyridine-N-oxide metal(II) except the one with largest possible ex- complexes, M(pyO)gX2, with X~ = CIO4, change interaction. However, in the BF7 BF4 or NO3 and M2+ a transition metal salt all configurations do appear with ion (Mn to Zn), are a class of isomorp- similar intensities. From the AB type of hous compounds (space group Ro). The spectra, the weak exchange interaction copper complexes have been studied in in the antiferrodistortive pairs could the pure as well as in a dilute form, be determined. For the CIO4 salt this doped into the zinc host. The reason for exchange coupling constant corresponds this interest is the Jahn-Teller (JT) to the -inter'chain constant existing in activity of the complex ion, in which the pure copper system. The above con- the CuOg moiety forms a nearly perfect clusions could be drawn from a compari- octahedron. This leads to static dis- son between experimental and calculated tortions at low temperatures (< 60 K), spectra (5,6). i.e. tetragonal elongations of the octa- hedra (1). Since the complex ions do not REFERENCES have ligands in common one might anti- cipate a random orientation of nearest- (1) Wood, J.S., Keijzers, C.P., and de neighbour (n.n.) complexes. However, Boer, E., Chem. Phys. Lett. 51, 489 this is not the case. The BF4 complex (1977). appears to be fevrodistovtive, i.e. all (2) Algra, H.A., de Jongh, L.J., and Car- axes of elongation are parallel, whereas lin, R.L., Physica B, 93, 24 (1978). the CIO4 and NO3 salts are antiferrodis- (3) Reinen, D., and Krause, S., Solid tovtive, i.e. the axes of elongation of State Commun. 29, 691 (1979). n.n. ions are mutually orthogonal. The (4) Wood, J.S., Keijzers, C.P., de Boer, change of magnetic properties on passing E., and Buttafava, A., Inorg. Chem. the JT phase transition is quite stri- 19, 2213 (1980). king. In the BF4 case it leads to two- (5) Van Kalkeren, G., Srinivasan, R., dimensional antiferromagnetism, and in Keijzers, C.P., Wood, J.S., and de the CIO4 and NO3 cases to pseudo-one-di- Boer, E., Solid State Commun. 44, mensional antiferromagnetic behaviour 1285 (1982). (2,3). These properties are explained by (6) Van Kalkeren, G., Keijzers, C.P., the structural ordering of the elongated Srinivasan, R., de Boer, E., and octahedra (4). In order to elucidate the Wood, J.S., Mol. Phys. 48, nature of the coupling between two neigh- 1 (1983). bouring Cu(pyO)?+ ions, the present EPR study has been undertaken on "semi-dilu- 63 te" (5-10%) Cu:Zn(py0)6X2 single crys- tals, with X~ = CIO4 and BF4. Below the transition from dynamic to static JT distortion, pairs of Cu(pyO)^+ ions are observed in both systems. In the C107 salt, antiferrodistortive pairs and a small amount of ferrodistortive pairs are detected. For both types of pairs all types of configurations are found, 196 Bulletin of Magnetic Resonance THE NATURE OF THE JAHN-TELLER EFFECT IN THE COPPER DOPED HEXAIMIDAZOLE ZINC DICHLORIDE TETRAHYDRATE COMPLEX E. de Boer, C.P. Keijzers, T. Jansen, G. van Kalkeren, and J.S. Wood Department of Molecular Spectroscopy, University of Nijmegen, The Netherlands 2+ The Cu(Im)5 (Im = Imidazole) ion third site is populated and takes part doped into the triclinic zinc host crys- in the exchange process. tal Zn(Im)(3Cl2.4H2O was reexamined with We conclude that at low temperature X- and Q-band single crystal EPR spec- only two out of the three energy minima troscopy over the temperature range 4 - of the Mexican hat potential surface 300 K. Earlier studies (1) on this com- are occupied and that there is no mea- pound claimed that at 77 K the spectrum surable tunneling between these minima. was indicative for Jahn-Teller tunnel- From the temperature dependence of the ing between three tetragonally elongated g- and hyperfine values it can be deri- configurations originating from the octa- ved that the energy well of the third hedral structure at room temperature. site is higher in energy than those of However, our more extensive measurements the other two sites by 100 to 140 cm"'. + show that the Cu(lm)^ ion in the zinc Examination of the crystal structure lattice is a case of strong Jahn-Teller affords an explanation for the energy coupling with significant interwell bar- differences between the three sites (2). riers. REFERENCES Cu(Im)6 Q-band 25 K (1) Rao, P.S., and Subramanian, S., J. Magn. Res. 22, 191 (1976). (2) Keijzers, C.P., Jansen, T., de Boer, E., and van Kalkeren, G., J. Magn. Res. 52, 211 (1983). Remarkably, at 25 K a spectrum is measured showing only two sites which are almost equally populated (see the figure, orientation of the crystal is arbitrary). The copper hyperfine split- ting stems from interaction with the four equatorial nitrogen atoms, in accor- dance with an elongated structure of the complex. As the temperature is increased the lines start to broaden. Above about 50 K also a shift of the lines is obser- ved. Finally, at room temperature four nearly equally intense lines are measur- ed. However, from the observation that this room temperature spectrum is almost isotropic, it must be concluded that the Vol. 5, No. 3/1* 197 THE EPR SPECTRA OF RARE EARTH S-STATE IONS IN GLASSY SYSTEMS C. M. Brodbeck* and L. E. Iton** *Department of Physics, Loyola University of Chicago, Chicago, Illinois 60626 USA **Materials Science and Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 USA I. INTRODUCTION III. APPLICATION Although the X-band EPR spectra of Applying the above criteria and ab Gd3+ and Eu2+ ions in a wide variety of initio computer simulations to the four glassy systems exhibit recurring promi- previous interpretations (1-4) of the nent features at g - 5.9, 2.8 and 2.0, glassy type spectra, we have found that there is serious disagreement in the all four previous interpretations are literature (1-4) concerning the distri- unsatisfactory, each failing to satisfy bution of crystal field parameters b^ one or more of the consistency criteria that can theoretically account for these imposed by the full range of experimen- features. We have performed a critical tal data. Our computer simulations, analysis of the glassy type spectra em- however, have revealed a satisfactory ploying (a) a set of consistency cri- interpretation of the spectra, which teria to determine if a given distribu- consists of a distribution of b^ that tion of bk*! is compatible with the full includes the rhombic component t>2 - 1 2 1 range of available experimental EPR and 0.064 cm" , b2 - 0.058 cm" . The bk B5.I.Cnipar§x, I>.Georgescux, R.Georgescux, l.Barnax, F.Beuranx, DIb& National Center for Physics, Mggurele, Bucharest, P.O. Box MG - 6, R - 76 900 , ROMANIA Heavy ions bombardment of po- The dependence of resonance lymers leads to the generation line parameters ( g factor, peak of active centers, due to the e- to peak linewidth, assymmetry nergy deposited by heavy ions, factor ,.») on degradation ti- around their trajectory, in the me and temperature as well as polymeric target. Because macro- the time stability of active molecules are insulators, this centers is investigated. The energy may increase significan- nature of active eenters is dis- tly the temperature in small vo- cussed. The dependence of acti- lumes around the incident parti- ve centers concentration on de- cle trajectory. Accordingly, if gradation time at a given ( con- large temperature gradients oc- stant ) temperature is related curs, pyrolysis-like active cen- to the mechanism of thermal de- ters may be generated during gradation in polycarbonate. heavy ions "bombardment of poly- The dependence of active cen- mers. ters concentration on degrada- The aim of this study is to tion temperature, for constant establish if the active centers periods of thermal degradation, generated during heavy ions is used to test the validity of bombardment of polycarbonate Arrhenius law and to estimate are or not pyrolysis-like acti- the activation energy. ve centers. Moreover, because Thin foils of polycarbonate thin films of polycarbonate have been irradiated with oxy- are used as solid state nuclear gen and sulphur ions accelera- track detectors ( s.s.n.t.d. ), ted up to about 60 MeV. Irradia- electron spin resonance ( e.s. tions have been performed in r. ) speetroseopy may give valu- vacuum, at room temperature, able informations concerning the although spectra have been re- physical and chemical canges as- corded on samples free to at- sociated to M latent tracks "• mospheric oxygen attack. Spec- Thermal degradation of poly- tra of polycarbonate irradiated carbonate has been investigated with electrons accelerated up by e.s.r. spectroscopy, using a to about 3 MeV as well as spec- JBS - ME - 3X spectrometer, ope- tra of gamma irradiated polycar- rating in X band. bonate are discussed in connec- Samples of polycarbonate have tion with the spectra of ther- been thermally degradated in air mally degradated samples. at constant temperatures, in the Possible correlations bet- range 620 K ; 850 K , during 5 ween " latent tracks " and ac- to 150 minutes. Some samples ha- tive centers generated during ve been thermally degradated in gamma irradiations, electron vacuum* Resonance spectra have beam irradiations, heavy ions been recorded at room temperatu- bombardment or thermal degra- re. Pew spectra have been recor- dation of polycarbonate are su- ded at liquid nitrogen tempera- ggested. ture. Vol. 5, No. 3A 199 DEPENDENCE OF LATTICE PARAMETER ON CRYSTAL SIZE FOR F.C.C. MATERIALSt L.G. Conti:: and B. D'Aguanno# Istituto di Chimica Generale, Universita di Roma, 1-00185 Roma, Italy The free energy G of a small cubic crystal bounded by {100} planes may be written as G = G + G + G . The elastic energy, G^ , can be found starting from the result of Sack (1) for a small circ- ular crack in a sphere and considering the crystal bounded by six square half- cracks. G depends on the surface tension y and G_ is the surface energy. Minimiz- ing G snows that 0 JO 40 60 80 SPECIFIC SURFACE (m2g-1) {1} 23 Fig. 1. Na NMR in NaCl (expt. points from ref. 3). K is the strain, or fractional change in size, strain and microstrain of fresher lattice parameter, F the surface free en- and older crystals. These data are con- ergy per unit area, and L the crystal sistent with eq. {1} and with the fact edge lenght. Until today it was usually that the fresher crystals contain point assumed that £ should vary as L (2). defects that dilate the lattice and dif- Figure 1 presents a theoretical fit fuse to the surface in a time of ^ 1 min. based on eq. {1} and the experimental 23Na NMR intensity in precipitated smokes REFERENCES of NaCl (3). The following model was cho- sen: quenched-in vacancy pairs are formed t Research supported in part by Nation- in NaCl in the precipitation process and al Research Council, Italy. then diffuse to the surface. The compres- tt Present address: International Centre sional strain at the critical radius (4) for Theoretical Physics, Trieste, was corrected by adding a differential Italy. strain according to eq. {1} and subtract- 1. R.A. Sack, Proc. Phys. Soc. _58, 729 ing a dilatational strain caused by the (1946). pairs. A uniform pair concentration, cfc 2. M.M. Nicolson, Proc. Roy. Soc. A228, 2 was allotted to vary with (D „ t/L P 490 (1955); R. Shuttleworth, Proc. between 0.01 (at t = 0) and O.flOl, the Phys. Soc. A63,. 444 (1950). latter value being a simulation of the 3. D.G. Hughes, G.C. Benson and P.I. subsurface space charge. No dislocation Freeman, J. Phys. Chem. Solids 28, contribution (3) was necessary. 2305 (1967). Diffusion (to the surface) of excess 4. N. Bloembergen, Defects Cryst. Solids, point defects that dilate the lattice in Rep. Conf., The Physical Society, rapidly formed microcrystals is evidenced London, 1955, p. 1. by the moire fringe experiments of 5. J. Woltersdorf, A.S. Nepijko and E. Woltersdorf et al. (5) on epitaxial Al. Pippel, Surface Sci. 106, 64 (1981). The lattice-parameter decrease from the 6. J. Crank, The Mathematics of Diffusion, center to the surface can be related fair- Oxford C.P., London, 1957, p. 86. ly well to the curves given by Crank (6). 7. C.R. Berry and D.C. Skillman, J. Cryst. From X-ray diffraction experiments on Growth 2, 141 (1968). AgBr (7) data are available about crystal 200 Bulletin of Magnetic Resonance ESR STUDY OF RADICAL PAIRS IN PHOTOLYZED R CSH AND R CSSH SINGLE CRYSTALS M. Geoffroy and R. Franzi Department of Physical Chemistry. University of Geneva (Switzerland) I. Ph CSSH. Single crystals of eigenvalues are in good accordance with Ph CSSH were grown from a solution in those previously reported for RSS ra- benzene/petroleum ether, at 22C. Such dicals. These results show that photo- a crystal was mounted in an insert de- lysis of Ph CSSH produces Ph CS*S which war containing liquid nitrogen and was is pairwise trapped. The following set studied by ESR. Photolysis of the sample, of parameters agrees with the experi- directly in the ESR cavity, by using a mental tensor : intramolecular S-S=2.04 500w Hg vapor lamp gives rise to very A, interradical distance between the anisotropic signals. Irradiation during S-S centers : 7.12 A. Such parameters 5 minutes leads to spectra whose inten- imply the following spin densities : sity was suitable for an angular vari- p(S ) = 0.52, p(S2)=0.47. ation study. The corresponding curves II. Ph_-jCSEL_ Similar experiments were for the XOY plane are shown in Fig 1. performe with Ph CSH crystals. The ESR The angular variations in three perpen- spectra were however strongly dependant dicular planes were fitted by using the upon the growing conditions. Slow evap- Hamiltonian : oration of solutions in ethanol produ- ces crystals which - after photolysis - H = HBSgh + ~%VS /I/ are characterized by very anisotropic spectra. These signals are not observed The existence of the interelectronic when Ph CSH has been sublimated and the spin interaction was confirmed by detec- solvant carefully degazed. Dopping ting a low intensity transition at half Ph CSH with Ph CSSH enhanced consider- magnetic field. ably the intensities of the anisotropic lines. As these spectra also exhibit a weak transition at half field, the angular variations of the spectra has been analyzed by using equation /I/. The corresponding tensors are given in Table 2. Table 2. ESR tensors (Ph CSH) g = 2.060 V = 92 G q = 2.023 £>2= -23.5 G Fig.l. Angular variation of the ESR Vol. 5, No. 3A 201 INDIRECT SUPERHYPERFINE INTERACTIONS OF CATIONS WITH V-TYPE CENTERS AND TRAPPED HYDROGEN ATOMS IN HOLMIUM-EXCHANGED Y ZEOLITE Lennox E. Iton Materials Science and Technology Division Argonne National Laboratory, Argonne, Illinois 60439, U.S.A. A new kind of superhyperfine inter- value represents a lower limit for the action was recently discovered by Ho^+ singlet ground state lifetime. Mehran et al. (1). This indirect The ISHFI weakens with increasing superhyperfine interaction (ISHFI) temperature. Eventually, at 77°K, the between impurity electrons and host inhomogeneous resonance of the V-type nuclei in Van Vleck paramagnets is centers is unbroadened even at 10 yW. induced by the large magnetic polari- However, the power-independent 7«4 G zability of the ground singlet elec- linewidth of the H atom resonances is tronic state of the Van Vleck cation. much broader than in the unexchanged It had previously been observed only Na-Y zeolite, and the H atom hf splitt- for Gd^+ impurities in HoVO, and PrVO, ing is 0.83$ lower. The excess broad- (2). The effect can be particularly ening and hf contraction are ascribed large in the case of Ho because of tp the direct shf interaction with large "J-effect" couplings between the '°5HO. These results constitute novel EPR observations of interactions singlet ground state of the ^ig Ho-^+ between defects and exchangeable ion and low-lying excited states (2,3) • cations in zeolites. We have observed ISHFI effects on neutral, spin S = 1/2 impurities for Work supported by the Office of the first time- They appear in the EPR Basic Energy Sciences, U.S. Department spectrum of Na-Y zeolite, partially of Energy. ion-exchanged with -'Ho^1 , which has been dehydrated and Y-irradiated. References Trapped H atoms and V-type center defects in the aluminosilicate frame- 1. F. Mehran, K. W. H. Stevens and T. work are formed as paramagnetic impuri- ties by this treatment. Crystal field S. Plaskett, Phys. Rev. B_20, 867 symmetries at the rare ion sites are (1979). orthorhombic or lower (4,5) , assuring a 2. F. Mehran and K. W. H. Stevens, ground singlet. The V-type center Phys. Repts. 85, 123 (1982). resonance width in unexchanged Na-Y 3. B. Bleaney, Bull. Magn. Resonance zeolite is 34 G; the H atom linewidth 2, 7 (1981). is < 1 G. In the Ho/Na-Y zeolite at 4. L. E. Iton and J. Turkevich, J. 4.2°K and 1 mW, M^^ ~ 125 G for the V- Phys. Chem. 82, 200 (1978). type center resonance, and the H atom 5. L. E. Iton, C. M. Brodbeck, S. L. signals are virtually unobservable. Suib and G. D. Stucky, J. Chem. This broadening is attributed to ISHFI. Phys., in press. ISHFI is mediated by a weak dipolar/exchange coupling. A novel line-narrowing is observed as the mi- crowave power level is increased. At 4.2°K and 100 raW, AH = 33 G and 7-4 G for the V-type centers and H atom signals, respectively. The narrowing is attributed to microwave decoupling of the ISHFI. Since the rf-limited lifetime of the impurity spin state in an H1 field of 0-9G is 6.3x10~8 s, this 202 Bulletin of Magnetic Resonance 2+ EPR STUDIES OF PHASE TRANSITIONS IN NH^Br DOPED WITH Cu 4 Asako Kawamori and J. Lakshmana Rao* Faculty of Science, Kwansei Gakuin University, Nishinomiya 662, Japan *Physics Department, S.V. University, Tirupati 517502, India EPR of Cu + doped in NH Br crystals has been studied at temperatures from (a) 295 to 542K by X- and K-band spectrom- eters. Cu occupies at the face cent- er of the bromince lattice and seems to be coordinated by two NH molecules by charge compensation in the crystal grown from basic aqueous solution. Below the transition temperature of 234K from the cubic phase II to tetra- gonal phase-Ill we could identify two kinds of Cu sites with tetragonal and orthorhombic symmetries respectiv- Fig. 1. X-band EPR spectra of Cu at ely, by application of uniaxial exten- 173K with H along one of the crystal sion along the tetragonal axis as sho- axes. In (a) arrows indicate position wn in Fig. 1. The spectra of Cu at of hfs due to Cu with tetragonal sy- the tetragonal site show increasing mmetry without extension, (b) shows hfs with decreasing temperature, while the spectra under extension and arrows the reverse tendency is seen for the mark that with orthorhombic symmetry. orthorhombic site in Fig. 2. The result has been analysed by a model in which antiparallel ordering of NH can be expressed by an order parameter p. The temperature dependnce of A is given by for the orthorhombic ssite3 , o * [p2 + (l-p)2]AA (1) We observed temperature dependence of optical transition A. -*E of Cu and have determined the temperature dependence of order parameter p from a 100 200 300 similar formula to Eq. (1). The mix- Temperature K ing parameter 6 of d 2 2 to the d 2 Fig. 2. The temperature dependence of orbital has been determined to be .0/6 hfs A.,measured by K-band EPR. Circles which is smaller-than .11 the value show the data with increasing tempera- obtained from Cu doped in NH4C1.[1] ture from 79K and crosses, from 54K. Table 1. The values of spin Hamiltonian parameters determined by K-band EPR T(X) g. A.. (10 4 cm"1) (10 4 cm"1) g/7/ 295 2.03210.005 2.18810.01 172.0+2.0 a, 28.3 79 2.03710.01 2.20810.02 140.9+5.0 for 0-site 2.027+0.01 2.16810.02 207.415.0 for T-site 54 2.03210.005 2.19910.01 225.812.0 ^ 39.9 Reference [1] N. Kuroda and A. Kawamori: J. Phys. Chem. Solids, 32_ 1233(1971). Vol. 5, No. 3A 203 NEW TRENDS IN THE SPIN RELAXATION THEORY R. Lenk, P. Descouts and H. Greppin University of Geneva, Switzerland The standard theories of NMR (Wangness spin Hamiltonian H as follows Bioch-Redfield or Kubo-Tomita) have not o elucidated the relationship of spin rela- 1/Ti = Z(g Tr H2)"1.L . (3) xation with the thermodynamics of irre- o o — versible processes. Following Zubarev (2) and Mori (3), the In order to contribute to this problem non-equilibrium and the local—equilibrium we present here the reformulation of the operators are given by the time-integral spin-relaxation theory : In the case of P -p. 3 X / H (t) dt • (4) ne loc OS S the non-equilibrium states, not far from — oo the thermal equilibrium, the spin relaxa- The application of eq. (4) to (1) tion is a linear process, governed by the leads to the non-equilibrium thermal flux Fouriers's phenomenological law (1), in from the spin system to the heat-bath which the heat flux J ^is proportional to the driving force : J = L^.X. The sim- X J p ( L. Onsager, Phys. Rev. 37, 405 (1931); 204 Bulletin of Magnetic Resonance 19 TEMPERATURE DEPENDENCE OF THE F NMR IN INTERCALATED ORIENTED GRAPHITES 1 K. Liiders, G. Roth, H.-J. Giintherodt Institut fur Atom- und Festkorperphysik, Freie Universitat Berlin, D-1000 Berlin 33, Germany 1 Institut fur Physik, Universitat Basel, CH-4056 Basel, Switzerland Temperature dependent NMR investi- At low temperatures, the solid gations have been performed on oriented state line width can be calculated, first stage CxSbF^ Graphite Intercala- using the method of moments. Good agree- tion Compounds (GIC), based on Highly ment with the observed line width is ob- Oriented Pyrolytic Graphite (HOPG). Up tained if one assumes that the interca- to now, CxSbF^ samples have been inves- lated molecules are build in with their tigated by NMR methods mainly at room molecular axis tilted by ~ 54° with re- temperature using powder samples (for spect to the graphite c-axis. example [1,2]). The samples were prepared by gas phase reaction using a two temperature method. For the NMR measurements, in- tercalated HOPG sandwiches of several slabs of 14 x 5 x^0.3 mm, isolated by mica sheets, were sealed under vacuum into pyrex tubes of 5 mm inner diameter. A cw-spectrometer at a field of 0.45 T and in the temperature range 4 - 300 K 100 200 300 was used. Temperature, K Fig.1. Temperature dependence of the F Fig. 1 shows the temperature de- NMR linewidth in first stage SbF5 inter- pendence of the ^9p line width for calated oriented graphite 19 CxSbF5. As the F line width of these compounds also exhibits a strong orien- tation dependence [3], which can be de- scribed by the equation . ,„ 6B(6) = [A2(2cos2e-1)2+A2]1/Z with REFERENCES A = 0.081 mT and A = 0.016 mT, the tempe- rature dependent measurements have been 1 L.B. Ebert, H. Selig, Mater.Sc.Eng. performed in the orientation 8 = 54°, 21, 177 (1977). where the line width is small. At low 2 H.A. Resing, F.L. Vogel, T.C. Wu, temperatures the line width is increased Mater.Sc.Eng. 4J_, 113 (1979). significantly with a pronounced step at about 150 K. 3 G. Roth, K. Liiders, H.-J. Giintherodt, 3rd Int. Conf. on Graphite Intercal. Comp., Pont a Mousson, France 1983. The temperature dependence of pure SbFc; is somewhat different: at about 4 L.B. Ebert, R.A. Huggins, J.I. Brau- 190 K the line width starts to increase mann, J.C.S. Chem. Comm. 1974, and reaches almost 0.8 mT at about 160 K p. 924. [4]. In both cases this transition does 5 T.C. Wu, F.L. Vogel, Carbon 2£, 225 not agree with the liquid solid phase (1982). transition occuring at about 280 K for pure SbF5 and at about 200 K for C SbF,, [5] . Vol. 5, No. 3A 205 ELECTRON PARAMAGNEi1U KtSUNAIMUt IN CUblC [ g (JUARTETS V.Lupei, C.Stoicescu, I.Ursu National Centre for Physics, IFTAR 76900, Bucharest, Romania The wavefunctions that form the with these, basis of the representations appearing 2 2 frequently in the cubic crystal field 2P = (5 cos 0- - 3 sin 9) k.g. decomposition of a J electronic level depend in an intricate way on the crys- tal field composition parameter x de- 2Q = |- (5 cos2G - 3 sin2 9- - fined by Lea, Leask and Wolf (1) or on the composition parameter 6 4 y = A6 (\/6 cosft + + (V21 cos& - 5 sin&) _ 7 206 Bulletin of Magnetic Resonance SPIN CORRELATION FUNCTIONS IN THE WEAK EXCHANGE HEISENBERG LINEAR CHAIN BIS(N- METHYLPHENAZINIUM) BIS-(MALEODINITRILEDITHIOLATO)COPPER(II), NMP2 Cu(mnt)2 P. Kuppusamy and P.T. Manoharan* Department of Chemistry, Indian Institute of Technology, Madras-36, India *Present Address: NIH/NIA/Gerontology Research, Baltimore, Maryland The metal dithiolato complexes are a .with the computed local field second class of interesting compounds which moments to get the Fourier Components of exhibit low dimensional cooperative phe- the spin correlation functions as well as nomina associated with their columnar the magnitude of the exchange coupling crystallographic packing. In particular constant. bis(maleodinitriledithiolato)Copper(II), Using the line width data in the ac* [Cu(S2C2(CN)2)2l^~ complexes show quite plane a consistent solution for these varied electrical and magnetic behavior coefficients was obtained by fitting in the small J regimel,2. EPR and mag- o procedure. The values obtained are netic studies have been shown to provide listed in the Table along with those an understanding about the spin dynamics obtained using the B-H and the A-W in such weak exchange regime. In this models. The J value used for the B-H communication we report our studies on model is the rms exchange given by the exchange interaction in bis(N-methy- T= fl J. phenazinium) bis(maleodinitriledithio- Both the models were able to predict lato)Copper(II), NMP Cu(mnt) - 2 2 the spin dynamics correctly. The ex- The title compound crystallises in the change values obtained from these models monoclinic space group P2]^/n with two (1500 G from B-H model and 1200 G from molecules per unit cell and forms a kind A-W model) also agree with that obtained of mixed stack with a donor-acceptor from susceptibility data. The rather sequence DAD-DAD along a axis. Static large values of g(0) and f(0) may sug- susceptibility measurements showed the gest 1-d exchange through NMP between exchange to be weak. Single crystal successive Cu(mnt)£ anions. EPR in the ac* plane, where the two TABLE sites are magnetically equivalent showed X-band(o) = 9.47 GHz) Fourier Components single exchange, narrowed lines with hy- (xlO-3 G-l) perfine dominated line width. In the ab and be planes two lines were observed. Four. Experi- B-H model A-W model The isofrequency plot simulated using Comp. mental (J=2100 G) (J=1175 G) crystal structure g-tensor directions and doped g values matches very well g(0) 0.64 - - - - with the experimental plot indicating - - g(w) 0.07 0.061 0.061 that the intersite exchange (between f(0) 2.79 ------inequivalent chains), if at all, is 0.15 0.145 0.161 very small. f(2u) 0.005 0.006 0.003 Cooling the system down to 4.2 K did not show any appreciable change. The References: line shape analysis for the lines in the 1. K.W.plumlee, B.M.Hoffman, M.T.Ratajack ac*, plane showed within experimental and C.R.Kannewurf,Solid State Comm., 15, limit, to be close to lorentzian. 1651(1974) The relative magnitudes of the various 2. K.W.Plumlee, B.M.Hoffman, J.A.Ibers spin Hamiltonians are Hzee > Hex > Hhyp and Z.G.Zoos, J.Chem.Phys., ^3,1926(1975) > H^-^p. In the literature there has not 3. M.Blume and J.Hubbard, Phys.Rev., Bl been much work reported on systems with 3815(1970). > zee Hex and we attempted to use the Blume-Hubbard^ and Anderson-Weiss models Vol. 5. No. 3/l» 207 APPLICATIONS OF NMR AND NQR TO THE NONDESTRUCTIVE EVALUATION OF FIBER REINFORCED COMPOSITES G. A. Matzkanin Southwest Research Institute San Antonio, Texas USA There is increasing interest in posite. A field-shifting method was applying magnetic resonance techniques used which is based on the effective to the nondestructive evaluation of or- shortening of the hydrogen spin-lattice ganic matrix fiber reinforced composites relaxation time at magnetic fields for and other polymer based materials (1). which the hydrogen NMR and nitrogen NQR Areas where magnetic resonance is useful energy levels are coincident. The sig- include the measurement of moisture and nals were observed at magnetic fields the characterization of modulus varia- corresponding to frequencies of approx- tions, degree of cure, impact damage, imately 3.406 MHz with half-amplitude hydrogen concentration and residual widths of approximately 1.5 MHz. The stress. Pulsed hydrogen NMR studies at signals from the composite were slight- 30 MHz on glass fiber and Kevlar fiber ly narrower and shifted in position composites environmentally conditioned compared with the fiber signals, a at 51.6°C and 95% RH show that the free result which may be associated with in- induction decay from the absorbed mois- ternal stresses in the composites. The ture consists of a large amplitude, fast large width of these level crossing decaying component associated with hy- signals is comparable to that reported drogen in rigid polymer molecules and a for NQR from amorphous materials (2). lower amplitude, slower decaying compo- Other studies related to applica- nent associated with hydrogen in the tions of NMR to composite materials in- mobile absorbed moisture molecules. The clude investigations of synthetic absorbed moisture free induction decay fibers. Spin-lattice relaxation times signals may be resolved into multiple at 3 MHz for nylon, acrylic and poly- components associated with moisture in ester fibers were 30ms, 70ms and 120ms, different states of binding. Particu- respectively, and a hydrogen-nitrogen larly, complex NMR responses were ob- level crossing signal was observed in served from Kevlar fiber reinforced com- acrylic fiber at a frequency of 2.767 posites as well as from Kevlar fiber MHz. Other related studies include the alone. The spin-spin relaxation time determination of environmental degra- measured from the free induction decays dation in the polymer insulation on for the absorbed moisture varied from electrical wires and in polymer-based 70 s to 250 s depending on the amount of printed circuit board material. moisture present. Good correlation was obtained between the free induction References decay amplitude at 200 s and the amount of absorbed moisture. Spin-lattice re- 1. G. A. Matzkanin, Proc. 14th laxation times were in the range of Symposium on Nondestructive Evaluation, 300ms to 600ms. April 1983 (in print). Hydrogen NMR - nitrogen NQR level crossing signals have been observed 2. M. Rubinstein and P. C. Taylor, from Kevlar fibers and in a Kevlar com- Phys. Dev. B9, 4258 (1974). 208 Bulletin of Magnetic Resonance THE ISOTROPY OF NONCRYSTALLINE MATERIALS AND THE EPR SPECTRA OF S-STATE IONS Al. Nicula, Eleonora Trif, S. Simon Faculty of Physics University of Cluj-Napoca Romania Studies on the noncrystalline materi- tors lead to an isotropic factor of 4.3 als provide evidence that the properties for Mn2* and Fe3* and of 6.0' for Eu2* of S-state paramagnetic ions do not and Gd3*. depend very much on the composition of Following the effect of the prepara- the amorphous matrix. tion temperature T on the lines with The EPR spectra of the S-state ions large geff factors from the EPR spec- Mn2\ Fe3* (3d5, 'Ss/O and Eu2\ Gd3 * tra of S-state ions in borate glasses (4f7, 8S7/2) in glasses and solutions one notes that the proportion of these exhibit resonance lines characterized by lines increases with Tp. This effect ge££ factors considerable higher than may be assigned to the increase in the 2.0. The characteristic feature of the number of paramagnetic ions for which EPR spectra of these ions in amorphous the isotropy conditions are accomplished materials consists of a line with iso~ as a result of the higher disorder 2 tropic geff factor at A.3 for Mn * and degree "frozen" into the glasses pre- for Fe3* ions and 6.0 for Eu2* and Gd3* pared at higher temperatures. ions. By proper heat treatment of glasses In order to explain the origin of containing S-state ions the lines with these isotropic signals, different isotropic geff factors disappears from structural models were proposed assuming the EPR spectra (3). . This may be that the fine structure term is larger regarded as the effect of destroying the than the Zeeman term and imposing iso- sample isotropy by the development of tropic Seff factors, i.e. the split- micro crystallites in the treated matri- ting of the Kramers doublets is indepen- ces. These results prove that the dent of the magnetic field direction. degree of disorder of an amorphous On the basis of the literature material also may be monitored by the results (1) and of our own (2) and tak- presence and proportion of the isotropic ing into account that there is not only EPR lines with large geff factors in a single type of microenvironment for the spectra of the S-state ions intro- the paramagnetic ions in glasses, one duced in these materials. may consider that the signal with geff 2 3 ^ 4.3 (for M.;n * and Fe *) and geff = REFERENCES 6.0 (for Eu2* and Gd3*) can arise from ions in sites of cubic, cubic with small (1) I. V. Chepeleva, N. V. Lezukin, DAN tetragonal distortion, or of tetragonal SSSR, 226, 2, 311 (1976). symmetry. This requires the presence in (2) E. Trif, Al. Nicula, Proc. Int. the spin Hamiltonian of the BJO* type Conf. "Amorph. Semiconduct.", .terms for Mn2* and Fe3* and B*0* type Bucharest, p. 123 (1982). terms for Eu2* and Gd3* ions. (3) S. Simon, Al. Nicula, Rev. Roum., The presence of these terms and the Phys., 28, 1, 57 (1983). addition of the isotropy of geff fac- Vol. 5, No. 3/4 209 APPLICATION OF NMR TO THE STUDY OF HYDROGEN IN INCONEL A. Raizman, J. Barak and D. Zamir Solid State Physics Dept., Soreq Nuclear Research Center, Yavne 70600, Israel D. Eliezer Department of Materials Engineering, Ben Gurion University, Beer-Sheva, Israel "The very low solubility of hydrogen in steels has thus far prevented the application of NMR to these materials. This difficulty was overcome by cathod- ic charging; enough hydrogen was intro- duced into Inconel 718 to obtain a meas- urable NMR signal. The NMR absorption line of % from one foil of Inconel 718 (a) with dimensions 10mm x 30mm x 0.1mm is determined by a paramagnetic shift K , the Lorentz field 4trM/3 where M=xH0, and the demagnetization field Hjj--4TrMsin 0. 6 is measured from the foil plane. The NMR frequency is given by f = YH [1 + K + 4TTM(3COS20 - 2)/3] FIG. 1. NMR of ^1 in an Inconel 718 foil (a) HQ parallel to the foil plane with ¥=4257 Hz/Oe. The experiments give (6=0), H,, is the center of the line, 3 K =-0.0027(5) and X=1.5xlO" emu/cm*. (b) Ho perpendicular to_the plane The large linewidth might come from (9=90°), center at Ha. H=(2H,,+Hx)/3, a distribution of K values and local Href=f/¥. dipolar fields, due to different H sites. The linewidth was found to increase with The spin lattice relaxation at 85K frequency (i.e. with H ) and to decrease exhibits a nonexponential behavior, with with T. This indicates that the broaden- slope varying between 2 msec and 7.5 msec. ing is proportional to the magnetization. This again shows that hydrogen occupies The measured transverse relaxation magnetically inequivalent sites or that was found to be exponential and T in- due to the wide line there is "spin dependent below 220K. T2 depends on the diffusion". The NMR features indicate charging conditions. A typical value interactions of hydrogen with paramagnet- for Inconel charged for 48 hours is ic centers in the metal. T2=200 ysec. The mechanism proposed for NMR of -4l was also observed in stain- the relaxation is the nuclear dipole- less steels SS316 and SS321, with dipole interaction in diluted samples. similar results. It seems that the NMR By calculating the second and the fourth technique naght become an important tool moments M2 and M4 in the diluted sample, in studying hydrogen in steels. 1 and using2 T2" = ^3/2/(i^)^, we This research was supported by a grant obtained the relation between T2 and the from the National Council for Research average concentration c of H in the met- and Development, Jerusalem, and the KFA, al. Lattice sums for the octahedral Julich, W. Germany. sites in the f.c.c. structure of Inconel 1= 6 yield T2~ 2.07xl0 c. This gives 1. A. Raizman, J. Barak, D. Zamir and c^O.25% for the above sample. Similar D. Eliezer, to be published. results were found for the tetrahedral 2. A. Abragan, The principles of Nuclear sites. Magnetism (Oxford,London,1961) Ch. IV. 210 Bulletin of Magnetic Resonance NUCLEAR SPIN-LATTICE RELAXATION IN TRANS DICHLOROETHYLENE H.S. SANDHU Physics Department, University of Victoria Victoria, BC, Canada V8W 2Y2 The spin-lattice relaxation time, Tlr The experimental values of the inter- of deuterons in oxygen-free samples of molecular dipole-dipole interaction are 100% C2H2Cl2 & (65% C2H2Cl2+35% C2D2C12) in reasonable agreement with the Bloem- has been measured at 4 MHz & 20 MHz bergen, Purcell & Pound (BPP) theory respectively. These measurements have modified to include the translational been carried out in the liquid phase microviscosity factor of 1/2 introduced between 48°C and -50°C using pulsed by Grier & Wirtz. The experimental nuclear magnetic resonance techniques. values of the intramolecular dipole- The most important relaxation dipole contributions do not agree with mechanisms contributing to Tj in the values predicted by the BPP theory diamagnetic liquids are given by the or the BPP theory modified to include equation the rotational microviscosity factor of about 1/6 introduced by Grier and Wirtz. (1/Tl> These results are consistent with the exPt d-d inter earlier reported results for 1,1,C2H2C12 d-d intra Work supported in part by the Natural Sciences & Engineering Council of Canada, University of Victoria & BC where (1/Ti) . is the actual observed 1 expt Ministry of Labour. value and <1/*i>d_d inter, (1/*l)d-d intra. (1/T1>spin-rot and ) are the contributions arising from the intermolecular dipole-dipole, intramolecular dipole-dipole, spin- rotation & quadrupole interactions respectively. The quadrupole inter- action can be eliminated by studying T^ of spin 1/2 nuclei (i.e. protons) since this interaction generally dominates T^ of nuclei with spin >^ . The other contributions to relaxation have been separated & the results show that the plots of (1/Ti), , . . & * l d-d xnter (1/Tl}d-d intra «e two parallel straight lines indicating that the spin-rotation interaction makes no contribution. This means there are only 2 interactions contributing to relaxation in this temperature range: intermolecular dipole-dipole interaction & intramolecular dipole-dipole interaction. Vol. 5, No. 3A 211 EPR (Cr5+) AM) MR (^Al) STUDY OP ALUMS AT HIGH PRESSURES AND LOW TEMPERATURES SHANTANU SIHHA AM> R.SRMIVASAN Department of Physics, Indian Institute of Science, Bangalore, India 560 012 The axial crystal field (CF) at the curve is seen in Fig.(i) at the point trivalent ions has been examined in where SO 4 fluctuations slow down, and several oC-alums by EPR and EMR as a this temperature increases with pressure. function of hydrostatic pressure and Finally a phase transition does take low temperature, unlike Walsh's studyt*) place in M^Cr alum at lower temperatures which was limited: to ambient and higher when the ammonium ion slow down and temperatures. EpR of Cr5* in KA1 alum, freeze into two possible distortions. KGr alum, HH4 Al alum, and H^Cr alum This phase transition temperature have been carried out in a high pressure increases with pressure. cell described elsewhere'*' and D has been determined as a function of P & T. REFERENCES: (Fig.l). 27A1 MR in KA1 alum and NH A1 4 (1) W.M.WaLsh Jr., Phys.Rev. alum has been performed at high pressure 1485 using a technique already described^1' (1959). and e2Qq/fi has been determined as a (2) S.Sinha and R.Srinivasan, Rev. Sci, function of pressure. Inst. (Communicated), The study has led to the following (3) G.Burns, Phys. Rev. 1j23_, 1634,(1961). conclusions:- (1) The study has permit- ted the separation of the temperature dependence of D and of e2Qq/h into impli- cit vibrational dependence. The impli- cit contributions scale with temperature in a manner to be expected from theory and the slope of a graph of D vs e^Qq/n. for different alums is seen to be the 3ame. This is along the lines suggest- ed by Burns^ but demonstrated experi- mentally for the first time (Pig.2). (2) The pressure dependent study has thrown light on the role of the So^.ions 1 -A ' -& ' 4 ' A> ' A ' * TEMPERATURE (*C) and their disorder in «-alums. The low- T£MPt«A?U«(*C) 'iSOBAftf OF ZEBO-HELO SPLITTING v* T ISOBARS OF 2ERO-FIELO SPIITTWO v* TEMPE- ering of symmetry of Cr'* ions observed BATURE IN HMtSC^k-itt^O RATURE IN NM, AKSQt^-ttHjO- through EpR at low temperatures is seen (a) to shift to higher temperatures on application of pressure. It mgy be Fig. 1 understood in terms of the slowing down of fluctuations of So4 ions. The appa- rent lowering of symmetry is caused by the displacement of Cr5* from the CE o^°- axis into three off-axis positions, and is not due to a phase transition in the host crystal. The increase of this symmetry-lowering temperature with pre- ssure can be understood in terms of the ?+ ionic radius of Cr and decreasing 0-07 008 0-09 0-10 Oil 0-12 inter~atomic distances with pressure. (3) A similar lowering of symmetry in COMPARISON OF FIELD GRADIENT M Al(:Gr) alum is not seen because of AT Mc3+ SITE, AS SENSED BY ESH(O) 4 AND NMR the persistence of 14 fluctuations. However, a change of slope in D vs T Fig. 2 212 Bulletin of Magnetic Resonance EPR AND OPTICAL ABSORPTION STUDIES OF Ni(II) IN A TRIGONALLY DISTORTED SUBSTITUTIONAL SITE IN;.Zn(en)3Cl2.2H20 S. SUBRAMANIAN* AND C. MURALIKRISHNA STRUCTURAL CHEMISTRY GROUP INDIAN INSTITUTE OF TECHNOLOGY, MADRAS 600 036, INDIA Metal ethylenediamine complexes are E=0.077 err."1. The results show that of considerable interest due to their the zero field tensor is entirely con- conformational lability. It is known trolled by the exact environment of the (1) that even in solids, equilibrium Ng chromophore so that the crystal field exists between various conformers. We geometry around Ni(II) is grossly tri- have examined the X-ray structure of gonal with a superposed small rhombic Zn(en)3Cl2-2H20 and have studied the distortion brought about by the slight EPR and optical spectra of Ni(II) doped differences in the Zn-N bonds. The single crystals of the title compound. unique axes of the D-tensor is along Single crystals of the title compound the resultant of any three mutually and 2-3% Ni(II) doped ones were grown perpendicular Zn-N vectors forming an from aqueous solution. The crystals are octant. D(xx) and D(yy) lie in the monoclinic, space group C2/C: a=8.790 triangular plane formed by the three b=13.961 and c=12.953 A; 6=93.37°; Z=4. nitrogens of the octant mentioned There are two spatially inequivalent above (see Fig. 1).. Zn(en)3 complex units per unit cell. The Zn-N bonds are not all equal. Projection of the Zn(N)6 octahedra on to the be plane shows that a common C3 axis for the two sites exists perpendicular to this plane. EPR spectra at X-band are spread over 0-8000 Gauss and are thoroughly distorted OZn by second order effects in D, this being larger than the X-band quantum. All Fig.l One of the Zn-Ng showing the dis- measurements were made in a Varian E-112 position of the D-tensor. Q-band spectrometer. In general orien- tations there were 8 distinct sites Polarised optical spectra showed characterised by zerofield split doub- bands at 11760, 18430 and 29190 cnT1 lets (S=l). The sites merged in pairs assigned to 3A2g^3T2g» A2g"^ Tlg and along the crystal!ographic axes. Also A2g"* Tiq(3p)- Analysis of the optical in the a*c plane there were only four spectra gives X=-250 cm"1, Dq=1176 cm"1, sites throughout. A careful projection B=800 cm"1 and C=4B. The values of D & E of the two ZnN5 octahedra onto the vari- together with the spin-orbit coupling ous crystal 1ographic planes indicate constant predicts that within the accu- that the unique axes of the D-tensor racy of g, it will be isotropic. Within L' coincide with the <111> axes of the two the time scale of D-anisotropy (en) groups distinct octahedra. A«Q-band powder are "static". ForbTdden transitions at spectrum could be unambiguously analysed g=4.5, showing at some orientations re- in terms of isotropic g-factor and ortho- solved N shf coupling have been observed. rhombic D-tensor, all sites being chemi- Also magnetic dipole allowed transitions cally identical. The parameters were have been located in the optical spectra. further refined by calculating the angu- These are under analysis. lar variation in the various crystal (1) J.R. Gollogly, C.J. Hawkins and J.K. planes using an exact diagonalization Beattie, Inorg.Chem.,10_, 317 (1971). procedure (2). The best fit was obtained (2) M.Kopp and J.H. Mackey, J. Compu- with g (||)=g(j>2.270±0.005, D=0.522 and tional Physics, 3, 539 (1969). Vol. 5, No. 3/if 213 EPR OF Ni(l) AND Ni(III) HEXAHYDRATE COMPLEXES IN Ni(II) DOPED ZINC AND MAGNESIUM TUTTON SALTS - BENT Ni-OH BONDS S. SUBRAMANIAN* AND C MURALIKRISHNA STRUCTURAL CHEMISTRY GROUP INDIAN INSTITUTF OF TECHNOLOGY, MADRAS 600 036, INDIA The present work describes the para- Ni(I) xz 214 Bulletin of Magnetic Resonance EPR SPECTRA OF TETRAGONAL COPPER CENTERS IN CaO J. Barak, A. Raizman and J. T. Suss Solid State Physics Dept., Soreq Nuclear Research Center, Yavne 70600, Israel We report on an electron paramagnetic resonance (EPR) study of three types of tetragonal copper centers in single crys- tals of CaO. The centers were observed in 100 G CaO crystals (grown in an electric arc furnace) into which Cu was incorporated by diffusion at 1400°C. A cubic Cuz+ spectrum1, as well as a spectrum due to Cu2+ pairs2, could also be observed, the latter only in heavily doped crystals. The ground state of the 3d9 Cu2+ ion in an octahedral crystal field is the orbital doublet 2E(t|e3). This doublet is further split by a tetragonal crystal field into two singlets JE> and |9>. The nature of the tetragonal distortion de- termines which singlet becomes the ground state. For a d9 ion it will be |£> with gB>gJL for an elongated octahedron and |9> with g,| I.Ursu, S.V.Nistor, M.Velter-Stefanescu National Centre for Physics, Bucharest, Romania An EPR study of several Fe+centers The octahedral center is stable at at various sites in X-irradiated NaCl room temperature (RT). Samples ir- (Tl, Fe) crystals is reported. The cen- radiated at 77K and subsequently ters are observed below 32 K, only in bleached with white light at 24OK crystals freshly quenched from 700K exhibit a second axial Fe+ center before irradiation. Such crystals X-ir- stable at RT. The axial crystal field radiated at 77K exhibit EPR transitions component is due to a negative ion from Fe+ions situated in substitutional vacancy trapped in the neighbourhood sites with either octahedral, axial or of a Fe+ ion, along an 100 direc- orthorhombic symmetry. By subsequent tion. thermal annealing at temperatures above 200K it is possible to observe the movement of the neighbour positive ion vacancy, reflected in the conversions: orthorhombic Fe+ 200K> axial Fe+ > 230K octahedral Fe+. 216 Bulletin of Magnetic Resonance ELECTRONIC STRUCTURE OF URANATE CENTERS IN ALKALI-FLUORIDE I.Ursu, A.Lupei and V.Lupei National Centre for Physics, IFTAR 76900, Bucharest, Romania Alkali fluorides doped with hexa- A different type of charge compen- valent uranium present luminescence sator having also a nuclear spin spectra with some sharp features (at I = 1/2, but giving smaller super- low temperatures)in the visible part of hyperfine splittings has been the spectrum and strong broad bands in observed in our_ spectra (1,2). The UV.Since different charge compensations influence of 0H~ impurities on these are possible many types of U centers spectra is presented. Sample with have been observed. The assignment of various contents of uranium and 0H~ the lines to structural models cannot (concentrations up to 5% molar) have be done only by luminescent spectra.EPR been grown. A connection between IR of U5+ centers, obtained by X or Y -ir- absorption bands due to OH , lumines- radiation of U doped samples, allows cence of U6+ and EPR spectra of U5+ the determination of the structure of is performed, allowing the elucida- some of these centers. tion of the structure of some centers. Combined EPR, luminescence,thermo- luminescence and IR absorption studies on various grown samples of uranium 1. A.Lupei, V.Lupei, I.Ursu, J.Phys.C doped LiF and NaF were performed.lt has 15, 5489 (1982). been proved that the main luminescent 2. V.Lupei, A.Lupei, Phys.St.Sol.(b), centers in LiF (emission lines at 77 K, 94, 301 (1979). 5277 A and 5185 A) and in NaF (emission lines at 77 K, 5636 A and 5528 A) aarre 5 uranate centers with a U05F ~ structure (1). The electronic structure of this uranate centers in terms of charge transfer transitions within a strongly distorted tetragonal C4v complex are discussed. Vol. 5, No. 3A 217 235y ENRICHMENT EFFECT IN NUCLEAR MAGNETIC RESONANCE OF IN GASEOUS URANIUM HEXAFLUORIDE I.Ursux, D.E.Demcoxx, P.Fitorixxx, M.Bogdanxxx x Faculty of Physics, University of Bucharest, MG-6 Bucharest xx Polytechnical Institute, 3400 Cluj-Napoca xxx Institute for Isotopic and Molecular Technology, C.P.700, 3400 Cluj-Napoca, 5 The nuclear magnetic resonance is The temperature dependence of able to detect the 235U isotopic longitudinal relaxation rates in sa- 235 enrichment by measuring 1% transverse turated vapors of UF6(0.7% U)is relaxation rates in liquid uranium similar to that of other molecular hexafluoride. compounds (SF6 , WF6, MoF6,etc). The NMR spectra and logitudinal rela- ii-[-3/2^ H law is not recognized in the 19 xation rates of F isotope in satura- case of enriched UF6(90%U). ted vapors of uranium hexafluoride This fact, corroborated with the have been measured as functions of homogeneous broadening of 19 F absorb- 235U enrichment,temperature and Larmor tion line in the high temperature do- frequency. main, proves that 19F- 235U scalar The line width and Tt values show coupling modulated by time fluctua- a pronounced dependence on235U enrich- ting quadrupole interaction of23\l is ment. This effect is smaller at higher the dominating relaxation mechanism. temperatures compared with the values The theory of this relaxation mecha- measured at about the room temperature nism is also presented. No frequency dependence was detected. 218 Bulletin of Magnetic Resonance 'H-NMR DETERMINATION OF THE MEIER-SAUPE ORDER MATRIX IN LIQUID CRYSTALLINE PHASES N.A.P. Vaz and J.W. Doane Department of Physics and Liquid Crystal Institute Kent State University, Kent, Ohio 44242 Deuterium NMR techniques were used to a result of a change in the mole- measure the residual spectral splittings cular conformation as it has been of perdeuterated rigid solutes dissolved suggested in the literature; (3) show in a liquid crystalline matrix which that the dissolved solute molecule is exhibit nematic, smectic A, B and/or C progressively excluded from the aromatic phases as a function of the temperature. core region to the flexible hydrocarbon The quadrupolar splittings were used region of the liquid crystalline host together with the knowledge of the rigid as temperature is lowered within the molecular geometry of the solute smectic phases; and, (4) calculate molecule in order to: (1) obtain exact the dihedral angles between the deu- values for the elements of the Meier- terium atoms at the linkage groups. Saupe order matrix and establish their These results also provide some clue temperature dependence within and as to the exact determination and across phase transitions; (2) show interpretation of the order matrix for that non-linearities in plots of the mesogenic molecule which, in the splitting ratios v£ temperature or past, has suffered from some assumptions vs another splitting ratio need not be related to the intramolecular configura- tional motions of the mesogenic molecules. Vol. 5, No. 3A 219 SPIN-LATTICE RELAXATION OF THE DIPOLAR ENERGY OF HIGHLY POLARIZED NUCLEAR SPIN SYSTEMS L.J. de Haas, C.M.B. van der Zon, W.Th. Wenckebach, N.J. Poulis Kamerlingh Onnes Laboratorium, Nieuwsteeg 18, 2311 SB Leiden, The Netherlands At present we are studying magnetic 100 ordering of proton spins in Ca(0H^2 (D (2). In these experiments the nuclear spin system is cooled to extremely low spin temperatures (below 1 microKelvin) by means of dynamic nuclear polariza- tion and adiabatic demagnetization in the rotating frame (ADRF) (3). During this procedure the lattice remains re- latively hot (about 0.5 K). Therefore spin-lattice relaxation processes will heat the nuclear spin system after the ADRF and the time available for experi- ments at extremely low spin tempera- tures is limited by these processes. Nuclear spin-lattice relaxation pro- cesses were studied in great detail for the case that the properties of the nuclear spin system can be calculated 0 by means of the high temperature ex- pansion, that means by an expansion to Fig.l. The dipolar relaxation tima ars lowest order in 1/kT (for a review see a function of the square of the nuclear ref. D.- polarization. We have extended the theory to low constant which is determined by the in- temperatures for the case the spin- teractions between the electron spins lattice relaxation is due to paramag- and the nuclear spins. netic impurities. For this purpose we We have checked eq.(l) by measuring used an extension of the Provotorov ij^ as a function of the nuclear polar- theory of magnetic resonance saturation ization Pn. The results are shown in that was presented previously (4,5). fig.l. This figure shows, that the ex- As an example we will give the result perimental results confirm our theo- for the spin-lattice relaxation of the retical prediction as given by eq.(l) dipolar interaction energy of the proton very well. spins in Ca(0H)2 in the case the nuclear spin system is paramagnetic and the lat- References: tice temperature is above 10 microKelvin (which in practice is allways the case). 1) J.C.M. Sprenkels, W.Th. Wenckebach, The relaxation process is theoretically N.J. Poulis, J. Phys. C: Solid State found to be exponential with a time con- Phys., L5, L941U982). stant Tij given by: 2) J.C.M. Sprenkels, W.Th. Wenckebach, 1-P2 N.J. Poulis, this congress. 1 1 C ^ (1) 3) A. Abragam, M. Goldman, Nuclear mag- netism, Order and Disorder, Clarendon le 3 n Press, Oxford, 1982, Chapter 8. 4) L.J. de Haas, W.Th. Wenckebach, where T^e is the spin-lattice relaxation N.J. Poulis, Physica 103A, 295(1980). time of the paramagnetic impurities, P e 5) L.J. de Haas, W.Th. Wenckebach, is the polarization of the spins of these N.J. Poulis, Physica 111B, 219(1981). impurities, and Pn is the polarization of the proton spins. The factor C is a 220 Bulletin of Magnetic Resonance DETERMINATION OF THE NUCLEAR POLARIZATION FROM THE MOMENTS OF THE NMR-LINE IN CYLINDRICAL SAMPLES C.M.B. van der Zon, P. Zonneveld, W.Th. Wenckebach, N.J. Poulis Kamerlingh Onnes Laboratorium, Nieuwsteeg 18, 2311 SB Leiden, The Netherlands At present we are performing experi- In our case of a cylindrical sample ments of dynamic nuclear polarization of Ca(0H>2 which has a hexagonal crys- of the_proton spins in Ca(OH)2 doped tal structure the summation over D|J with 02~centres. The aim of these ex- where |?i-rJ| Vol. 5. No. 3/4 221 DYNAMIC NUCLEAR POLARIZATION USING PHOTO-EXCITED PARAMAGNETIC CENTRES H.W. van Kesteren, G.J. Schenk, W.Th. Wenckebach, J. Schmidt, N.J. Poulis Kamerlingh Onnes Laboratorium, Nieuwsteeg 18, 2311 SB Leiden, The Netherlands Huygens Laboratorium, Wassenaarseweg 78, 2333 AL Leiden, The Netherlands It has been shown to be possible to dp enhance the polarization of nuclear 25 dt spins by means of dynamic nuclear po- 7 10~ /sec) larization using photo excited triplet states (1),(2). In these experiments f 20 that were first performed by Hausser 1 ' / and his group a molecular crystal is 15 irradiated with light and thus paramag- 1 netic triplet states are created. Then 10 a microwave field with a frequency near the resonance frequency of the triplet electron spins is applied. As a result 5 a considerable enhancement of the po- larization of the proton spins in the 0 1 1 1 1 10 20 30 iO crystal is observed.. -AIMHz) We have performed such studies on the Fig. 1. The rate of growing of the system phenanthrene-fluorene at liquid nuclear polarization vs. the amplitude helium temperatures using 9.5 GHz of the field modulation (in ESR-fre- microwave irradiation. We were able to quency units). enhance the nuclear polarization by a factor 90 to a value of 3% (3). Subse- saturated and thus used for dynamic nu- quently we performed several experiments clear polarization. Hence the rate of in order to establish the mechanism by the polarization increases if the am- which the nuclear spins are polarized. plitude of the modulation is increased. The electron spin-lattice relaxation The existence of spin packets in the rate is about 100 s~l (4) while the ESR line of the triplet spins implies decay rate of the triplet states is that the mechanism of dynamic nuclear 0.28 s~l (5), so the triplet spins are polarization must be the so-called in equilibrium with the lattice. This solid effect (6). implies that the mechanism of dynamic nuclear polarization should be similar References: to one of the mechanisms observed in 1) G. Maier, U. Haeberlen, H.G. Wolff, dynamic nuclear polarization using K.H. Hausser, Phys.Lett. 25A,384(1967). centres that are paramagnetic in the 2) M. Deimling, H. Brunner, K.P. Dinse, ground states. K.H. Hausser, J.P. Colpa, J. Magn. Reson. 3_9, 185(1980). The experiment deciding which one of 3) H.W. van Kesteren, W.Th. Wenckebach, these mechanisms is involved in our J. Schmidt, N.J. Poulis, Chem. Phys. case, is given in fig.l. There the ef- Letters 89, 67(1982). fect of a modulation of the stationary 4) D.A. Antheunis, B.J. Botter, J. field during dynamic nuclear polariza- Schmidt, P.J.F. Verbeek, J.H. van der tion is shown. Fig.l shows that the rate Waals, Chem. Phys. Letters 36, 225(1975) at which the nuclear polarization grows is larger if the amplitude of the modu- 5) H. Sixl, M. Schwoerer, Z. Natur- lation is increased. This result can be forschung 25A, 1383(1970). explained if we assume that the ESR-line 6) A. Abragam, M. Goldman, Nuclear of the triplet spins consists of "spin- Magnetism, Order and Disorder, Claren- packets" that can be saturated separa- don Press, Oxford, 1982, Chapter 6. tely by the microwave field. If we apply field modulation, more spin-packets are Bulletin of Magnetic Resonance U NUCLEAR MAGNETIC ORDERING OF PROTON SPINS IN Ca(OH)2 AND THERMOMETRY BELOW 1 MICROKELVIN J.C.M. Sprenkels, W.Th. Wenckebach, N.J. Poulis Kamerlingh Onnes Laboratorium, Nieuwsteeg 18, 2311 SB Leiden, The Netherlands As was shown by A. Abragam and M. If the ADRF is performed in such a Goldman and their co-workers it is pos- way that the nuclear spin temperature sible to reach nuclear spin tempera- is negative, we observe a ferromagnetic tures below 1 microKelvin by means of ordering with a domain structure. This dynamic nuclear polarization (DNP) and was proven from measurements of xi and adiabatic demagnetization in the rota- Xii (4). We also studied the relaxation ting frame (ADRF)(1). Under these cir- behaviour when the nuclear spin system cumstances magnetic orderings of the warms up after the ADRF. This relaxa- nuclear spins occur. tion behaviour appeared to be due to We have performed such experiments in spin diffusion between the various Ca(0H)2 containing O^-centra as para- domains. From the speed of this diffu- magnetic impurities. The DNP was per- sion process we could deduce the aver- formed at 0.5 K by means of 75 GHz age domain size. microwave irradiation. The ADRF was per- formed in a magnetic field of 6 T par- References: allel to the crystalline c-axis. Before 1) A. Abragam, M. Goldman, Nuclear Mag- and after the ADRF, NMR-signals of the netism, Order and Disorder, Clarendon proton spins were recorded. From these Press, Oxford, 1982, Chapter 8. signals the entropy S, energy E, and 2) J. Marks, W.Th. Wenckebach, N.J. parallel and transverse susceptibili- Poulis, Proc. of the Joint ISMAR-AMPERE and x of tne ties xil l nuclear spin sys- int. conf., the Franklin Institute tem were calculated. From 3E/8S also Press, 1981, p. 229. its absolute temperature Td was deduced. 3) C. Urbina, J.F. Jacquinot, M. In fig.l we plotted xi as a function Goldman, Phys. Rev. Lett. 48,206(1982). of 1/Td for the case that the ADRF was 4) J.C.M. Sprenkels, W.Th. Wenckebach, performed in such a way that the nu- N.J. Poulis, J. Phys. C: Solid State clear spin temperature was positive. It Phys., 15, L94K1982). is clear that a phase transition occurs at a temperature of about 0.4 micro- Kelvin. The magnetic ordering is prob- ably helicoidal (2), (3). 5.0 Fig.l. xi as a function of 3=1/Td for Td>0. Voi. 5, No. 3A 223 NMR STUDIES OF TETRACYANOPHENANTHROLINE COMPLEXES OF IRON(II) 1 2 3 4 B. V. Agarwala, K. V. Ramanathan and C. L. Khetrapal ' 1) Allahahad University, Allahabad, India 2) Indian Institute of Science, Bangalore, India 3) Raman Research Institute, Bangalore, India 4) National Institutes of Health, Bethesda, Maryland, USA I. INTRODUCTION bon and proton (3). If such a situation is realistic, signals due to aliphatic The aromatic diimines such as 1,10- protons and carbons must be observed in phenanthroline (phen) and 2,2'-bipyridine the *H and the 13C-NMR spectra. How- (bipy) and their derivatives occupy cen- ever, no such signals were present ruling tral positions in coordination chemistry out conclusively the existence of the (1) and their metal complexes have poten- structures of this type. tial use in solar energy systems as they The proton spectrum of the ligand can oxidize hydroxides to yield oxygen shows 4 groups of lines corresponding to (2). Though such complexes have been 4 sets of nonequivalent protons. The subjected to many investigations in order proton and the carbon-13 spectra of the to establish their structures but the complex in D20 correspond to two discrete derived results are many a time anomalous phenanthroline moieties and hence the re- and questionable (3). The tetracyano- sults show that the complex is present in phenanthroline iron (II) complex was sub- two different forms. The proton spectrum jected to detailed NMR investigations and in DMSO-dg recorded soon after the prepa- the results are reported in the present ration of the solution also shows the communication. presence of two species. One form, how- ever, disappears with time (>1 Hr) and II. EXPERIMENTAL finally the spectrum corresponding to only one form is observed. Addition of The complex was prepared by the stand- D20 in the DMSO-dg solution brings back 1 ard procedure (4) and the proton and the the two separate spectra. The ^C- carbon-13 NMR spectra were obtained in a spectrum also corresponds to these re- Bruker WH-270 FT-NMR spectrometer. The sults . complex was dissolved in heavy water The more stable form is assigned as (D20) and dimethylsulphoxide (DMSO-d6) the cis-complex and the other form may for such a purpose. Nearly one hundred be the dimeric species as proposed for scans were accumulated for the proton the osmium tetrachlorobipyridyl complex spectra while 12,000 free induction de- (5). cays were necessary to obtain a reason- able signal to noise ratio for the car- IV. ACKNOWLEDGEMENTS bon-13 spectrum in DMSO-dg solution and 3000 transients for that in the D20 The authors are grateful to Drs. G. solution. Nord and E. D. Becker for helpful dis- cussions. They are grateful to the III. RESULTS AND DISCUSSION University Grants Commission, New Delhi for the financial assistance by awarding The proton NMR spectrum of the com- National Associateship to one of the pound has earlier been investigated in authors (BVA). D20 solution and the results have been interpreted in terms of a non-symmetric IV. REFERENCES substitution in the phenanthroline nu- cleus leading to the formation of a cova- 1. R. D. Gillard, Coord. Chem. Rev. lent hydrate containing aliphatic car- ^L6, 67 (1975). 22i+ Bulletin of Magnetic Resonance 2. C. Creutz and N. Sutin, Proc. Natl. Acad. Sci. (USA), _72., 2858 (1975). 3. R. D. Gillard, L. A. P. Kane-Maguire and P. A. Williams, Trans. Met. Chem. jL, 226 (1976); J2, 12, (1977). 4. A. A. Schilt, J. Am. Chem. Soc. 8Z, 3000, 5779 (1960). 5. D. A. Buckingham, F. P. Dwyer, H. A. Goodwin and A. M. Sargeson, Aust. J. Chem. 17, 315 (1964). Vol. 5, No. 3A 225 MR EVIDENCE H)R THE EXISTENCE OP A REORIENTATIONALLY DISORDERED PHASE IN MBBA S.ARUMU&Jffll, S.V. BHAT AND R.SRINIVASAN Deparianent of Physics Indian Institute of Science Bangalore-560 012 INDIA N(.p-methoxy-ben2grlidene) p-n-butylan- using the Bruker WH-270 spectrometer. iline (MBBA) has been examined by wide- In the cooling cycle at 11i°C, tiie line NMR and "high resolution MR from spectrum suddenly shows isotropically 5O°C to -70°C and evidence for a new motionally averaged spectrum showing phase between the nematic and solid clearly tiiree chemically shifted phases has been obtained. components, which were much broader Consistent with published reports(i), than the components of the high reso- the isotropic phase is characterized by lution spectrum observed in the iso- a single narrow line (peak to peak tropic phase at 50°C. This broadening width AH = 0.24G) indicating both posi- may be due to the high viscosily of the tional and orientational disorder and liquid at this temperature. This high the nematic phase exhibits a moderately resolution spectrum progressively resolved multiple line broad spectrum broadened on cooling. ( AH = 3.7G) expected for tiie orie- The phase transition was further ntation'aily ordered phase. The wide- observed by dissolving the solute mole- line NMR of the nematic phase is moni- cule GH, CN in the MBBA. Dipolar split tored as a function of temperature. While cooling, at 11PC. the nematic lines from CR, groups of CH, CN were phase spectrum disappears as expected, observed in the nematic phase. On but instead of the line broadening cooling to 11°C these lines disappeared expected of the poly crystalline solid and a broad isotropic line at the expe- phase, a strong narrow central line cted position of CH3 developed while at develops. 5Ms narrow line persists to the same time, the earlier described about -5°C (cooling cycle) and reduces high resolution spectrum of MBBA deve- drastically in intensity. Below this loped. temperature the central line which is A careful DSC run of the sample also broader than the earlier narrow line, showed a phase change a few degrees persists along with the expected broad below the end of the nematic phase. polycrystalline dipdlar broadened The precise nature of the phase spectrum. This central component is observed is not yet understood, beyond believed to be a part of the 3-spin ^ the fact that it appears to be isotro- spectrum of rotating methyl groups. The pic due presumably to orientational disappearance of this component below disorder and motion, with a correlation -68°C indicates the slowing down of these time much longer than that in the high motions at these low temperatures. temperature isotropic phase. This behaviour suggests that the nematic phase first goes into an iso- REFERENCE: tropic liquid like phase for a few degrees before finally freezing into 1) Y.S.Lee, Y.Y.Hsu and D.Dolphin the solid. In order to further examine Liquid crystals and Ordered fluids, this, three other tests have been Vol.2, 557-366. performed. Plenum press (New York-London),1974* A high resolution proton magnetic: resonance at 270 MHz has been performed 226 Bulletin of Magnetic Resonance 13C CHEMICAL SHIFT AS A MEASURE OF SPIROCONJUGATION EFFECT Michal BALAZY Stereochem. Lab. Jagellonian University Krakow, POLAND The idea that polyunsaturated pairs. 2his observation is in spirans might show spiroconjuga- complete agreement with the tion through overlap of the two earlier UV and/or PE evidences perpendicular JC systems was first for spirocon^ugation in these suggested for the case of two compounds (3;. interacting even conjugated sys- A(ppm) tems by Simmons and Fukunaga (1), and for two odd ones by Hoffmann, Imamura, and Zeiss (.2) in terms * 66.3 of orbital interactions between the two JC- systems. It was shown recently (3) that heterocyclic 40.0 spirans - with four heteroatoms attached to spirocarbonatom - may also reveal spirocongugation. The present study is the first 35.4 investigation of spiroconjugaticn that uses 130 NMR technique. She difference between chemical 19.6 shifts of the spirocarbon atom in spiroconjugated spirans and the related carbon in its refe- rence half compounds depends on 6.4 the magnitude of spiroconjugaticn effect measured from Uv and/or photoelectron spectra. This dif- Fig 1. Differences of chemical ference was measured in 15 pairs shifts of indicated carbons in of spiro-half compounds and was selected pairs of compounds. measured for the first time amaag heterocyclic spirans, eg. spiro- (1) H.E. Simmons and i1. imkunaga, orthocarbonates and spiroortho- J.Am.Ohem.boc, 89, 5208 (1967). thiocarbonates. The size of the (2) R. Hoffmann, A. Imamura, and difference falls into three re- G.L1. Zeiss, J.Am.Chem.oOC, 89, gions: 66-35» 30-14 and below 10 ppm for spirans revealing 5215 (1967). strong, medium or weak (if any) (3) S. omolinski, i-». oalazy, a. the spiroconjugative effect, res- Iwamura, x. ougawara, Y. Kawada, pectively. and K. Iwamura, Bull.Chem.ooc. Jpn., 55, 1106 (1982). The observed downfield shifts of the central carbons as we go from half to spiro compound are ascribed to contraction of the radius of the carbon 2p orbitals by bonding to the increased num- ber of the p orbitals or lone Vol. 5. No. 3A 227 ELECTRON SPIN-ECHO CHARACTERIZATION OF COLLISIONS BETWEEN REACTIVE RADICALS IN SOLUTION"1" D. M. Bartels*, R. G. Lawler, and A. D. Trifunac* Chemistry Division, Argonne National Laboratory Advances in the time resolution of pure second order kinetics. An earli- EPR spectroscopy have made possible er publication from this laboratory the study of EPR signals from free (2) examined the kinetic behavior of radicals in solution on a sub-microse- the high- and low-field hyperfine cond time scale. Of particular inter- lines of the radical •CH2COO" est in these systems are non-reactive following pulse radiolysis of 0.5 _M radical encounters which result in KOAc solutions. The time-resolved spin dephasing and Chemically-Induced signal from these lines is dominated Dynamic Electron Polarization by the polarizing effects of radical (CIDEP). Observation of these phenom- pair CIDEP. Detailed analysis also ena constitutes a probe of the diffu- indicated a concentration-dependent sive nature of the radical encounters. relaxation which could result from the A pulsed EPR spectrometer has been Heisenberg exchange interaction in assembled at Argonne National Labora- non-reactive radical encounters. tory to study radicals produced with The central radical line could not the 3 MeV Van de Graaff accelerator be studied previously due to a strong (1). Electron spin-echos are genera- sample tube background signal. By in- ted as a function of time after a troducing the sample as a liquid jet radiolysis pulse to follow the radical (3), we have now been able to observe reaction. Very large radical concen- the central line which is free of the trations (~10 3 K) can be generated effects of CIDEP. Figure 1 shows the with this equipment, so that the echo spin-echo amplitude of this line fol- amplitude is strongly affected by lowing a 400ns radiolysis pulse. CIDEP and "collisional" dephasing. Based on the modified Bloch equations Radiolysis of N2O saturated aqueous used to describe the magnetization of acetate solutions yields a clean sin- reactive radical systems (2), the sig- gle radical system which decays by nal from this center line should de- crease monotonically (second order chemical decay) if concentration-de- pendent spin dephasing is unimport- ant. The distinct maximum in Figure 1 confirms that non-reactive radical en- counters cause significant electron spin dephasing in this system. (1) A.D. Trifunac, J.R. Norris, and R.G. Lawler, J. Chem. Phys., 71 4380 (1979). (2) J.A. Syage, R.,G. Lawler, and A.D. Trifunac, J. Chem. Phys., 77, 4774 (1982). (3) D.M. Bartels, R.G. Lawler, and A.D. Trifunac, J. Mag. Res., submitted for publication. 0 4 8 12 16 TIME ((jsec) Figure 1: Spin-echo amplitude of the Work performed under the auspices of central radical anion line following the Office of Basic Energy Sciences, radical creation. U. S. Department of Energy. 228 Bulletin of Magnetic Resonance ESR, OPTICAL AND CRYSTALLOGRAPHIC STUDIES OF DICHLORO COPPER(II) AND ZINC(II)/COPPER(II) 15-CROWN-5 ETHER COMPLEX. R. Debuyst , F. Dejehet, M. Spirlet, J.P. Declercq, M. Van Meerssche. UNIVERSITE CATHOLIQUE DE LOUVAIN Laboratoires de Chimie Inorganique et de Cristallographie. B-1348 Louvain-la-Neuve, Belgium. Concentrated Copper(II) System. data (an intense band at 13.3 kK with a shoulder at 11.4 kK; two other less pre- The general structure of the comple- cise bands at 12.4 and 10.4 kK) can be xes consists of chains formed by alter- reproduced within the framework of an nating cycles of crown-ether and chro- A.O.M. calculation (3) with the follo- mophore entities. Contrarily to the ana- Wing arameters: e 5300 e logous bromine complex, which has a flat- P a(O12)~7- ' a(ci) = nn tened tetrahedral geometry (1), the ste- -490' " 0 and 'e , .=-53""•"0 cm p I ex s /e reochemistry of the chromophore in the n(tot) a present case is that of an approximate 0.4; k =k =0.8 and k =0.77. square-base pyramid. The fifth atom, in The cancellated optical bands for the 2 apical position, is the oxygen atom of isomers are: 9.5(9.4),10.9(10.8),12.6 a methanol molecule arising from the sol (12.4),13.3(13.1)kK corresponding to the z2,xy,xz,yz •• x2-y2 transitions. The cal- vent. Two distinct types of CuCl (H 0) 2 2 2 culated g-values are 2.088(2.089),2.056 CH_0H chromophore stereochemistry exist (2.057),2.341(2.342)and the eigen vectors within the same unit cell (fig. 1). are directed almost along the molecular bonds. Diluted Copper-Zinc System. As the analogous ZnBr2 complex (4), FIG. 1 s (CioH2o05)ZnCl2(H20)2 i- composed of ZnCl2(H20)2 deformed tetrahedral chromo- x phores alternating with crown-ether cyc- les. The ESR powder spectrum of Cu(II) embedded in this compound reveals the presence of two species, one with g//> gt and the other with g//< gA- The former could be due to a Copper ion substituting the Zinc ion, and the lat- ter to a Copper ion directly coordinated to a crown-ether. The two species also appear in frozen concentrated methanol 2(1) solutions. A similar situation was encountered in Owing to the instability of the compound the bromine complex.(4) under normal conditions (departure of the methanol molecule), the analyses are per- (1) E. ARTE, J. FENEAU-DUPONT, J.P. formed on freshly prepared crystals coa- DECLERCQ, G. GERMAIN, M. VAN MEERSSCHE, ted with liquid paraffin. Acta Cryst. B35_, 1215 (1979). Single crystal g-values (g =2.064, g = (2) F. DEJEHET, R. DEBUYST, J.Phys.Chem. 2.161, g =2.271) are trans formed in to Solids,38,517 (1977). mean molecular ones (g =2.090, g =2.053, (3) A. BENCINI, D. GATTESCHI, J.Magn. g =2.343) with the ass umptions ythat the Resonance, 34, 653 (1979). g axis coincide with the Copper-Metha- (4) F. DEJEHET, R. DEBUYST, F. MULLIE, J. nol Oxygen bond and that the two dis- M. ARIETTA, G. GERMAIN, M. VAN MEERSSCHE, tortion isomers have identical g-values. J.Chim.Phys., in the press. (2). The molecular g-values and the optical Vol. 5, No. 229 DETECTION OF INTRAMOLECULAR SUBSTITUENT INTERACTION IN ALIPHATIC MOLECULES BY 13C NMR SPECTROSCOPY Helmut Duddeck Ruhr-Universitat Bochum, Abteilung fiir Chemie, Postfach 102148, D-4630 Bochum 1, FRG 1 X Intramolecular substituent and the one-bond carbon-fluorine interactions can be monitored by coupling constants suggests that determination of non-additivities oT(CF) reflects this kind of (NA) of individual substituent interaction as well (1,2). induced 13C chemical shifts (SCS). In 4ax-substituted adamanta- A great variety of di- and trisub- nones j4, however, NA effects in- stituted derivatives of conforma- dicate that a completely different tionally rigid molecules, e.g. - probably through-space - inter- adamantanes and bicyclo [3.3.1]- action is operative (1). Recently, nonanes, was investigated, and it it was shown (1) that in compounds was found that the transmission containing both types of substi— mechanisms of these interactions tuent arrangements simultaneously, and the magnitude of their effects e.g. in 5_, the NA effects are are strongly dependent on the largely additive, i.e. the diffe- nature of the substituents as well rent mechanisms do not affect as their stereochemical position. each other seriously. This is im- For example, in 4ec*-substituted portant to know for the prediction adamantanones 1_ and 2e<3,4ec?-disub- and understanding of l^G signal stituted adamantanes _2 it was shifts in highly substituted ali- shown that a hyperconjugative phatic compounds. interaction between X and 0 or Y, respectively (cf. 3^, is appro- priate to explain the observed NA effects. An excellent correlation between those NA effects for the C-4 signals in 1 and 2_ with X = F (1) H. Duddeck, Tetrah. 39_, 1365 (1983) and preceding papers, (2) H. Duddeck and M.R. Islam, Tetrah. 3_7, 1193 (1981). 230 Bulletin of Magnetic Resonance ON THE STRUCTURE OF THE HYDRATED URANYL ION M. Aberg, Do Ferri, J.Glaser , IoGrenthe Depto of Inorganic Chemistry, The Royal Institute of Technology, S-100 kk Stockholm 70, Sweden Very little is known about the In more concentrated solutions, hydration of the uranyl ion in where the initial concentration of solutiono The PMR data of Fratiello the uranyl ion is 2-3 M, the hydration et alo (i) were interpreted by number decreases to U.6(±0.2)o It is assuming the hydration number of fouro shown that our results are not . A hydration number of six is deduced dependent on the acetone-d^ concentration„ from thermochemical measurements„ When ordinary acetone is used instead The mogt common coordination number of acetone-d/- , lower hydration number is for UOp complexes is five in the obtained, Thxs effect is probably caused solid state„ The present PMR by the overlap of the dominating acetone investigation was undertaken in order peak with the peak for the 'free' water„ to determine the hydration number This type of systematic error will be of the uranyl ion by repeating and larger in the study of Fratiello et alo extending the measurements of due to the lower magnetic field used Fratiello et al. Our data, collected by them (60 MHz) which may explain at 200 MHz, at about -80°C in (water)- their value of U.O(±O,U) for the hydration (acetone-d^) mixtures result in the number of the U0^ ion., hydration number of i+o9(±0o2) for the initially 1 M aqueous solution of UO (ClO^) « This result is in agreement with X-ray diffraction data (1) A. Fratiello et al. J. Phys o Chem- obtained for exactly the same solution» Jh, 3T26(1970)O Vol. 5, No. 231 SPINECHO NMR-S.PECTROSCOPY FOR THE ANALYSIS OF DEUTERATED COMPOUNDS J. R. Wesener, P. Schmitt, and H. Giinther University of Siegen, FB 8, D-5900 Siegen 21, Germany Analytical methods that allow Sequence A is experimentally the a quick and unambiguous characte- simplest. It uses the well-known rization of labelled carbon sites SEFT technique (1) for phase se- are of vital importance for deu- lection (1/J) or signal elimina- terium labelling studies in orga- tion (1/2J). The degree of deute- nic and bio-organic chemistry. ration is measured via the split- The analytical problem involved ting present due to 1^C,^H spin- is solved in many cases by using spin coupling. Difference spec- NMR techniques. It is, therefore, troscopy can be applied with ad- of interest to show how ^ ^C spin vantage in many cases in order to echo spectroscopy with gated de- minimize signal overlap. coupling can be used for this Sequence B needs 2H decoup- purpose. ling facilities and consequently Considering the possible expe- a different lock system (e.g. ^F rimental set-up, ^H as well as ^H lock). It allows a rather complete coupling can be applied for the edition of '^C subspectra from C, modulation of ^^C magnetization. CH, CH2, CH3, CD, CD2, CD3, CHD, Accordingly, a ^H or ^H decoupler CHD2, and CH2D groups (2). must be used, respectively. Addi- Finally, sequence C, which we tional ^H decoupling should be call TANDEM-SEFT, uses two conse- used also in the latter case for cutive spinecho experiments and spectral simplification and NOE is the most versatile approach to enhancement. The following pulse solve the problem under conside- sequences can thus be realized: ration. In particular, the follow- ing experiments can be performed: 1) selective detection of quarter- (A) 13C: 90°-^-180°-^- FID nary carbons; 2) phase selection for CHn groups with elimination H: of all signals from CDm and CHnDm groups; 3) phase selection for 13 CDm groups with elimination of (B) C: 90°-r2-i80°-r2- FID signals from CHn and CHnDm groups; 2 4) phase selection for all groups H: due to their ^H and 2H multiplici- ty. (C) 13C: 1. D. W. Brown, T. T. Nakashima, and D. L. Rabenstein, J. Magn. Reson. 4£, 502 (1981). 2. P. Schmitt, J. R. Wesener, H. Gunther, ibid52_, 511 (1983). J. R. Wesener and H. Gunther, Org. Magn. Resonance, in press, 232 Bulletin of Magnetic Resonance CP/DD/MAS CARBON-13 NMR STUDY OF NATIVE AND REGENERATED CELLULOSE A. Hirai, F. Horii, and R. Kitamaru Institute for Chemical Research, Kyoto University Uji, Kyoto 611, Japan CP/DD/MAS carbon-13 NMR spectra have line does for ramie and cotton. This been obtained on native and regenerated suggests that there is some difference cellulose. The resonance lines of Cl in crystalline structure among native and C4 carbons in the $-l,4-glycosidic cellulose. linkages and C6 carbons of CH2OH groups On the other hand, the crystalline can be resolved into the crystalline line of both the carbons split into two and noncrystalline components and the peaks for regenerated cellulose. chemical shifts for each component are The chemical shifts of noncrystalline determined. The molecular conformation component of Cl, C4, and C6 carbons for of the crystalline and noncrystalline native cellulose were almost the same components are discussed by examining as those for regenerated cellulose. the chemical shifts of the carbons in The line width of the noncrystalline terms of torsion angles about the component of the Cl carbon is much corresponding bonds. narrower than that of regenerated The solid-state spectra were cellulose, suggesting narrower distri- observed at 25 and 50 MHz in a JEOL JNM bution in the torsion angle Vol. 5, No. l/k 233 NMR SPECTRA OF ORIENTED TRIMETHYL PHOSPHINE OXIDE AND SULPHIDE 12 1 3 C. L. Khetrapal, * A. C. Kunwar and M. R. Lakshminarayana 1) Raman Research Institute, Balgalore-560 080, India 2)National Institutes of Health, Bethesda, Maryland, USA 20205 3) University of Agricultural Sciences, Bangalore-560 065, India I. INTRODUCTION nuclei in systems of the type (CH-j) 3 PX have 3-fold axes of symmetry, the Molecules containing 3 methyl groups inter- and intra-methyl HH dipolar and a phosphorus nucleus (spin 1/2) and D couplings ((DHH)inter ( HH>intra> constitute spin systems of 10 inter- can be estimated from the approximate acting nuclei in proton NMR spectra guessed geometry and Dpg. The spec- 13 without C-satellites. Analysis of tral parameters so evaluated serve as the spectra of oriented general 10 spin reasonable starting points for the systems without symmetry is quite com- final iterative analysis which was plicated and many times double reso- carried out with the help of the LEQUOR nance or isotopic substitution proce- program (2). The number of assigned dures have been followed to achieve spectral lines was 71 for (G^^PO and this. However, the presence of 3 86 for (CH3)3PS in the final analyses. methyl groups and a heteronucleus such Values of the derived coupling con- as phosphorus simplify the situation. stants are: DpR = -58.99 + 0.09, This is demonstrated in the present (%H)intra = 249.21 + 0.04, (DHH) inter communication and the results on tri- = -95.5 ± 0.03 and (Jpg)^ r = 0.33 methyl phosphine oxide and sulphide ± 0.04 Hz for the oxide. The respec- ar e pr es ent ed. tive values for the sulphide are: -33.92+0.003, 140.63+0.01, -57.79 II. EXPERIMENTAL +_ 0.01 and 0.37 + 0.01 Hz. The rPH/rHH and the bond angle CPX are The proton NMR spectra of the title 1.355 and 112.3° for trimethyl phos- compounds in Merck phase IV were re- phine oxide and 1.344 and 112.7° for corded on a Bruker WH-270 FT-NMR spec- the sulphide. trometer. A 3.9 weight percent solu- The spectra provide intermethyl HH tion of the oxide was studied at indirect coupling constant (JHH)inter -320K where as for the sulfur compound, to a reasonable precision. The bond the solute concentration and the tem- angle increases from 112.3° to 112.7° perature of the experiment were 4.3 when X is replaced from 0 to S. The weight percent and 302K respectively. corresponding PH distance (rpjj) decreases by about 0.8% on a similar III. RESULTS AND DISCUSSION replacement, under the assumption that the intramethyl HH distance An inspection of the spectra indi- (rjj|j) in the two compounds is the cated several repeated spacings cor- same. responding to (JpH+^Dpg) where Jpg and Dpjj are the indirect and the direct IV. REFERENCES couplings between phosphorus and pro- ton and hence this quantity could be 1. J. B. Hendrickson, M. L. derived in a relatively straight- Maddox, J. J. Sims and H. D. Kaesz, forward manner. A knowledge of JpH Tetrahedron ^£, 449 (1964). (-13.4 and -13.0 Hz for the oxide and the sulphide respectively from the 2. P. Diehl, H. P. Kellerhals and spectra in isotropic media (1)) W. Niederberger, J. Mag. Res. 4_, 352 yielded Dpn- Since the interacting (1971). 234 Bulletin of Magnetic Resonance DETERMINATION OF INDIRECT SPIN-SPIN COUPLINGS BETWEEN HETERONUCLEI FROM NMR SPECTRA OF ORIENTED MOLECULES 1,2 1 3 C. L. Khetrapal, A. C. Kunwar and N. Suryaprakash 1) Raman Research Institute, Bangalore - 560 080, India 2) National Institutes of Health, Bethesda, Maryland, USA 20205 3) Indian Institute of Science, Bangalore - 560 012, India I. INTRODUCTION II. EXPERIMENTAL NMR spectra of molecules oriented The liquid crystals used were Merck in individual liquid crystals do not phase IV ( AX > 0) and ZL1-1167 permit separate evaluation of indirect (Ax < 0). A 4 weight percent solu- spin-spin (Jjj) and direct-dipolar tion of the chloro compound disolved (Djj) couplings between heteronuclei in 0.3:1 weight ratio of phase IV and i and j since these parameters appear ZL1-1167 showed the coexistence of the as the sum (Jjj + 2 Djj) in the two orientations at 328K. The 6 Hamiltonian. However, the spectra in weight percent solution of the bromo mixed liquid crystals of opposite compound in similar weight ratio of diamagnetic anisotropies (Ax) which the two liquid crystals provided two show the coexistence of two types of coexisting spectra at 313K. The spectra orientations at a critical concentra- were recorded on the Bruker WH-270 tion and temperature, provide such in- spectrometer. Values of the parameters formation (1, 2). At the critical were obtained using the LAOCOONOR pro- point where the two spectra coexist, gram [3] on a DEC-10 computer. the dipolar couplings due tothe situ- ation corresponding to Ax > 0 (D-jj's) III. RESULTS AND DISCUSSION are -2 times those due to Ax < 0. Hence, the spectra at the critical The dipolar couplings corresponding point provide (J-H + 2 Djj) and to Phase IV type of orientation are: p = (Jji - permitting the evaluation D-J2 -1264.49 _+ 0.04, D-j3 + D23 = Of J jj and Djj individually. -466.73 ± 0.06, D14 = -36.52 ± 0.05, The results on two organo selenium D15 + D24 = 13.63 ± 0.05, D16 + D26 = compounds, namely phenyl selenyl -87.05 ± 0.06 and D36 = -18.57 ± 0.26 Hz chloride and phenyl selenyl bromide for phenyl selenyl chloride. For the (structure 1), thus obtained are dis- bromo compound the respective values cussed in the present communication. are: -1648.8 + 0.2, -526.2 ± 0.2, -39.1 + 0.3, 56.4 ± 0.3, -106.2 ± 0.3 and -24.6 + 0.4 Hz. In the ZL1-1167 type of orientation all the dip!oar coupling parameters are half with opposite signs compared to those for the phase IV type of orienta- tion. (6)SeX = CI,Br (Ji6 + J26) and J36 were evaluated (5)H from the spectra at the critical point as 5.2 ± 0.3 and 0.0 + 0.4 Hz for the (4)H^Y^H(2) chloro compound and 3.1 ± 0.4 and 0.0 ±0.5 Hz for the bromo. It was not H(3) possible to determine J]6 and J26 indi- vidually to any acceptable precision. The spectra were sensitive to the sums Structure 1 (D13 + D23), (0T5 + D24) and (Di^ + D26) rather than the individual coupling con- stants; hence, these values are reported. Vol. 5, No. 3A 235 The six dipolar coupling parameters were used to determine 4 relative in- ternuclear distances and the two order parameters. It was found that the phenyl ring protons in the chloro com- pound nearly retain the regular hexa- gonal geometry whereas minor devia- tions outside the experimental error were observed for phenyl selenyl bromide. The distance of the selenium from the nearest proton is about 2% larger in the bromide compared to that for the chloride. The value for the chloro compound is 1.257A° assuming a value of 4.30A0 for r24 as the scaling distance. IV. REFERENCES 1. C. L. Khetrapal and A. C. Kunwar, Mol. cryst. Liq. cryst. 72^ 13 (1981). 2. C. L. Khetrapal and A. C. Kunwar, Chem. Phys. Lett. 82_, 170 (1981). 3. P. Diehl, C. L. Khetrapal and H. P. Kellerhals, Mol. Phys. 15, 333 (1968). ~ Bulletin of Magnetic Resonance AN EPR STUDY OF THE PRIMARY RADICAL Ph2P(O)CH2Cl" OBSERVED AT 3 K P.-O. Samskog, C. M. Arroyo, L. D. Kispert* and M. Geoffroy** *Chemistry Department, The University of Alabama, Tuscaloosa, AL 35486 **Department of Physical Chemistry, Sciences II, University of Geneva, 30 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland I. INTRODUCTION angles of 12.1° and 13.0° to the respective C-H bond directions, Organic molecules containing hetero- indicating that some rearrangement had atoms are very sensitive to ionizing occurred upon radical formation. radiation. It is however difficult, in Upon thermal annealing to approxi- general, to propose a reaction mechan- mately 170 K, Ph2P(O)CH2Cl" decayed and ism because not enough is yet known Ph2P(O)CH2 was formed. Photolytically about the identification and structure this same process occurred at 3 K when of the primary radicals and the associ- the X-ray irradiated sample was bleach-, ated thermal and photolytic stability. ed. An INDO molecular orbital calcula- An EPR study of Ph2P(O)CH2Cl crystals tion using the RHF/CI method and X-ray irradiated in the dark has shown modified for use with halogens (2) that the primary radical Ph2P(O)CH2Cl~ showed that the observed couplings and is trapped at 3 K. A description of the corresponding direction cosines its structure is given below. could be predicted only if the C-Cl bond length increased from 1.8 to 2.2 A* upon II. EXPERIMENTAL electron addition. The chlorine hyper- fine couplings are similar to those X-ray irradiation and EPR measure- reported for CF3C1" (3) and are clearly ment were carried out in the dark at not those expected for an adduct (4). 3 K using a Janis Supervaritemp Dewar All the above evidence indicates and a TEm X-band cavity. A Kratos that the observed radical, Ph2P(O)CH2Cl~, variable wavelength 1 kW (Hg/Xe lamp) is a 0-type radical which was formed by illumination system was used for the lengthening of the C-Cl bond by bleaching experiments. approximately 0.4 A and reorienting the C-H bonds upon electron attachment to III. RESULTS AND DISCUSSION the C-Cl bond. The EPR spectrum consisted of ACKNOWLEDGMENTS couplings to one chlorine, one phos- phorus and two protons. Angular Special thanks to H. Oloff and J. rotation at 3 K yielded the following Hvittermann for use of their INDO pro- hyperf ine couplings (Gauss) : A(-^^Cl) = gram and to B. Nelson and D. Close for 1 helpful suggestions. (40.4, 17.9, 16.1); A1( H) = (-24.0, 1 -17.2, -13.1; A2( H) = (-25.0, -16.4, -9.0), and A(31p) = (42.1, 33.6, 23.8). REFERENCES The g tensor components were equal to (1) G. Bernardinelli and R. Gerdil, 2.0021, 2.0040 and 2.0046. Comparison Cryst. Struct. Comm. 8^ 921 (1979). to crystallographic data (1) showed (2) H. Oloff and J. Huttermann, J. Magn. that the directions of the maximum Resonance, 4£, 415 (1980). •"Cl coupling and the minimum g value (3) A. Hasegawa, M. Shiotani and F. were located 5.1° and 4.1° respectively Williams, Faraday Discussion Chem. from the parent C-Cl bond direction, Soc. 63_, 157 (1977). suggesting that the unpaired electron (4) E. D. Sprague and F. Williams, J. was located in the C-Cl bond direction. Chem. Phys. 54, 5425 (1971). However, the minimum proton tensor directions for proton 1 and 2 made Vol. 5, No. 3A 237 SOLID STATE C-13 NMR STUDY OF CHAIN DYNAMICS AND MORPHOLOGY OF CRYSTALLINE POLYMERS R. Kitamaru Institute for Chemical Research, Kyoto University Uji City, Kyoto 611, Japan The solid-state C-13 nmr provides an the melt or dilute solution with T]_'s insight into the molecular chain con- obtained by a standard CP/DD/MAS formation as well as the chain dynamics technique. It is noted that a pretty of solid polymers. A brief review will amount of the crystalline components be given of our recent work particularly are associated with rather pronounced of linear polyethylene. molecular chain motion, particularly It is known that the DD/MAS C-13 nmr for the solution-grown sample with spectrum of polyethylene comprises two shorter lamella thick. Such a molecular lines with different chemical shifts, motion in the crystalline region at room the one ascribable to the trans-trans temperature was also suggested by our conformation (aave) and the other to previous ^-H broad-line nmr work of this the motionally averaged chemical shift polymer. of the noncrystalline component (o^so)• Fig. 1 shows DD/MAS C-13 nmr spectrum w Bulk-Crystal obtained by a pulse sequence(TT/4-1800S) (TV//,-1600s) for a polyethylene at room temperature. 6/. There are evidently observed the two s lines. The ^ave i- associated with two Fig. 1. DD/MAS Spectrum different T^'s, the one ca. 800s and the of Linear Polyethylene, Crvstallized from the Melt. other 1.6s. However, the origin of this line should entirely be sought in the crystalline region since the integrated fraction of the line in the total spec- trum is in good accordance with the crystalline fraction estimated from density measurements and X-ray dif- fraction analysis. By use of a pulse sequence (IT/4-10S) "* ppui ^ ppm the waiting time(lOs) of which is much Table I. Xass^Discrioutior. ar.c ~^*s si Different Conpon*nts in ?o Sctapies, Crystallized fcither from the Me it or Diiutfc Solution. shorter than the longer T-^ but enough longer than the shorter T^ of the • 0.10.14 -• • mobile crystal tion analysis of such a spectrum yields 32 ppm ^ \ =0.23 s 0.39 » noncrystalliae the ratio of the mass fraction between the crystalline component with the shorter T-^ and the noncrystalline com- |2. solution-crystal) ponent. Eventually we could estimate the full mass distribution of all phases 0.19 • rigid cryftal with different T-^'s in the structure. 34 ppm The table summarizes the results for two 059 --'•« mobSt crystal samples crystallized isothermally from 32 ppm-T,= 0.23s 0.22 noncrystalline (Oiso) 238 Bulletin of Magnetic Resonance ESR LINEWIDTH AND BONDING PARAMETERS OP Cu(il)-L-ISOLEUCINE COMPLEX B.N. Misra and R. Kripal* Department of Physics, University of Allahabad, Allahabad, India. I. INTRODUCTION In the present investigation, more covalent than the out-of-plane ESR study in three phases-polycrys- pi bonding. talline glass and solution combined The solution ESR spectrum gave with the optical absorption and asymmetric four hyperfine lines of magnetic susceptibility have been unequal intensity. The data on g done to obtain information about the and A are 2.1268 and 1.304 x 109 magnetic and non-magnetic inter- s"1 respectively. Various theore- action as well as about the nature tically evaluated(5,6) linewidth of bonding in Cu/L-Isoleucine parameters a, b, c / d, d^g and complex. alongwith r are 2.8010, 1.6271, 0.1014, 0.0030, 76.71G, O.695X10"11 II. EXPERIMENTAL s and 1.90 JP respectively. The The Cu(ll)-L-Isoleucine complex experimental parameters Reino Laatikainen Department of Chemistry, University of Kuopio P.O.B. 138, SF-70101 Kuopio 1Q, Finland By using various NMR techniques a celles. In this way normally nearly lot of detailed information from micel- degenerated HNMR signals of the ethoxy lar systems can be derived. In the units of polyoxyethylene-lQ-stearyl present report it will be shown that ether can be split into a well-resolved a sort of radial image of a micelle multiplet showing one signal from each can be derived by using suitable aro- unit. matic dopants and the standard resol- The outlook of the multiplet and the ution enhancement technique of Fourier level of resolution is dependent on the Transform NMR. The dopant is needed dopant and reveals new information from to develop a regular radial magnetic the order of surfactant molecules in suscebtibility gradient in the micelle micelles. In a few cases results and a window function is applied for strongly indicate regular and most FID to reduce the information from probably spherical micelles. nuclei of short T? and unperfect mi- 240 Bulletin of Magnetic Resonance TIME RESOLVED FLUORESCENCE DETECTED MAGNETIC RESONANCE OF TRANSIENT RADICAL IONS Steven Lefkowitz* and Alexander Trifunac* Chemistry Division, Argonne National Laboratory Ionizing radiation of solutions in Submicrosecond time resolution is nonpolar solvents produces transient achieved using a pulsed Van de Graaff radical ions which play a crucial role electron accelerator and a pulsed mi- in the subsequent chemistry and phys- crowave source. ics of these systems. ESR of these We have employed FDMR to study var- radical ions can provide valuable in- ious alkane solvent-scintillator solu- sight into their structure and dynam- tions (2). Cyclohexane is of partic- ics. The study of these radical ions ular interest, as it possesses a high- by microwave detection (cw or pulse) ly mobile radical cation species, with is difficult because small radical ion a mobility ten times greater than concentrations are obscured by the diffusion controlled. FDMR of cyclo- large yields of solvent alkyl radi- hexane-scintillator systems showed cals. spectral components not attributable FDMR is a uniquely selective method to scintillator radical ions, which for obtaining the time resolved ESR were assigned to the cyclohexane spectra of radical ions formed by hole. The hyperfine resolution indi- pulse radiolysis in nonpolar solvents cated that this hole was physically (1). The experiment depends on the trapped, and not rapidly hopping like spin selectivity of the initial ioniz- the mobile hole. ing event to preferentially form the Addition of triethylamine (TEA) to solvent cation (hole) - electron radi- this system yielded the FDMR spectrum cal pair in the singlet spin state. of TEA«, formed by scavenging solvent Added scintillators scavenge electrons holes (3). In cyclohexane, the growth and/or holes, with spin conservation, of TEA* FDMR intensity with time has to form new singlet radical ion shown that scavenging was diffusion pairs. At high magnetic fields, S-T controlled, indicating that TEA* was mixing will occur, forming equal num- not formed by reaction with the mobile bers of S and T radical pairs. Only cyclohexane hole, thus supporting the S pairs can recombine to form an exci- existence of the trapped hole species. ted scintillator singlet state, which can then fluoresce. Application of (1) J.P. Smith and A.D. Trifunac, J. microwaves resonant with an ESR trans- Phys. Chem. 85 1645 (1981). ition of either radical ion will cause (2) J.P. Smith, S.M. Lefkowitz and T +T. transitions, thus depleting the A.D. Trifunac, J. Phys. Chem., 86 TQ state. S-»-To mixing will then de- (1982). crease the number of S pairs and at- (3) S.M. Lefkowitz and A.D. Trifunac, tenuate the scintillator fluores- J. Phys. Chem., in press. cence. FDMR is performed by measur- ing the fluorescence intensity of an Work performed under the auspices of irradiated scintillator solution as a the Office of Basic Energy Sciences, function of the magnetic field Division of Chemical Science under strength while applying X band micro- Contract Number W-31-109-ENG-38. waves. FDMR thus yields a superposi- tion of the ESR spectra of the radical cations and anions which recombine to give scintillator fluorescence. Vol. 5, No. 2h] A SEMIQUANTITATIVE ACCOUNT FOR THE WATER H NMRD OF COBALT(II) PROTEINS Ivano Bertini," Claudio Luchinat," Marcello Mancini,'and Gabriele Spina^ Dipartimento di Chimica e Istituto di Fisica Superiore, University of Florence, Italy. There is an ever growing interest predicted for several values of the angle in the use of water H NMRD on solutions G between the metal-proton vector and the of paramagnetic metalloproteins. The po- principal axis of the D tensor, as compa- w = tential of the technique is however re- red with the Solomon theory. The sT2e l stricted by the intrinsic limitations in dispersion is on the average less pronoun- the Solomon theory of the electron-nu- ced and smoother, and the inflection point cleus dipolar coupling (1). The major is shifted to higher field. obstacle to the application of the theo- The most refined and complete water ry as such to cobalt(II) proteins is the ^H NMRD data available refer to cobalt(II) presence of zero field splitting. The substituted human carbonic anhydrase B (3) effect of ZFS has been analyzed by Lind- (Figure 2). A comparative fitting of the ner (2) for complexes of axial symmetry data to our equation and to the Solomon in the slow rotation limit, but equations theory confirms the validity of our treat- 1 were only derived for S=l: for ZFS>T2e~ ment. = the dispersion at us T2e l does no longer appear. For half integer spin, however, the 1/2 -«--l/2 spin transition is expec- ted to be unaffected by ZFS. Following Lindner's approach we have derived an analytical expression for Tn"^- of water protons bound to high spin co- 1 balt (II) ions in the limit ZFS » T2e~ , which is likely to hold for most real sy- stems. Figure 1 shows the NMRD curves .01 .1 1 10 100 proton Larmor frequency (MHz) Figure 2.- Paramagnetic contribution to the NMRD of water protons in solutions of 2.9 mM cobalt(II) substituted human carbo- nic anhydrase B at pH 9.9 and 25°C (3) best fitted to the Solomon equation ( ) and to our equation ( ) . magnetic field REFERENCES Figure 1.— Magnetic field dependence of 1) I. Solomon, Phys. Rev., 99, 559 (1955) the paramagnetic contribution to nuclear 2) U. Lindner, Ann. Phys. (Leipzig), 16, T^\ values induced by an S=3/2 spin sy- 319 (1965) stem in the presence of axial ZFS ( ) 3) I. Bertini, R.D. Brown, S.H. Koenig, and as compared to the Solomon theory ( ) . C. Luchinat, Biophys. J., 41, 179 (1983) Bulletin of Magnetic Resonance ESR PARALLEL-EDGE LINES OF SLOW TUMBLIG SPIN PROBE IN RIGID LIQUID CRYSTAL Keiichi Ohno Faculty of Engineering, Hokkaido University, Sapporo 060 Japan The ESR spectra of slow tumbling nitroxide radical in the rigid p,p- methoxy benzylidene n-butylaniline(MBBA ) exhibit three step shoulders at reso- nant magnetic fields of the molecules with the symmetric axes oriented nearly parallel to the applied static magnetic field. An analytic expression is deriv- ed for the difference of parallel-edge linewidths (A B) between outer hyper- fine compornents in the second deriva- tive spectra. It is described as a sum of a rotational correlation time depen- dent term and a term which contains the effects of magnetic field Bq quenching 0 200 400 the samples at 77K and the degree of Bq (mT) orientation distribution. The first Fig.2 Variation of the difference of 2 term has been predicted to vary as the linewidth,A B with Bq 2 tc"-'-' at a limit of fc-^ooby Kivelson of liquid crystal before quenching. This and Lee,l) whereTc is the rotation term is based on that in the presence of correlation time. The second term is magnetic field in a nematic mesophase determined to be inverse proportional the probability for orientation is modi- 2 2 to (l/e|+AXBq /2kTq) , where Q9/f2 fied by a factor exp(-U/kT), where U= means the standard deviation from the -AXBq(3cos20-l)/6 and Q is the angle be- mean of the Gaussin distribution,&%(= tween a molucular axis and a director. X//-XJ the anisotropy in diamagnetic The measurements are conducted using susceptibility, and Tq the temperature X-band ESR spectrometer with a magnetic field modulation of 100 KHz and 80 Hz to take second derivative spectra. The sam- ples are put into pyrex glass tubes (ca. o OmT 4 mm$) and sealed off after d.egassing. * 20 . . Figure 1 shows the temperature depen- o 30 '• dence of A2B at selected Bq. Figure 2 • 50 " depicts the dependence of the defference •500 upon Bq at each elevated temperature. The solid lines mean least square fitted curves for the observed values to the above expression. Reference 0.06 1) D. Kivelson and S. Lee, J. Chem. 150 200 250 Temp.(K) Phys. 75, 5746 (1982). Fig.l Differences of the linewidth A B as afunction of temperature Vol. 5, No. 14 The N Nuclear Ouadrupole Resonance of Azoles and other H-Bonded Species: Joint Theoretical and Experimental Studies *Michael H. Palmer and John A.S. Smith** Department of Chemistry, University of Edinburgh*, West Mains Rd., Edinburgh EH9 3JJ; Queen Elizabeth College**, University of London, Campden Hill Road, London W8 7AH 14 The three N NQR resonance frequencies References (v , v_, v ) per N atom are rarely all observed in classical NQR on the solid 1. E.A.C. Lucken, "Nuclear Quadrupole azoles, such as imidazole (I) and Coupling Constants", Academic pyrazole (II). This arises from the low Press, London, 1969. resonance frequencies and (often) 2. M. Redshaw, M.H. Palmer and piezoelectric properties [1]. A further R.H. Findlay, Z.Naturforsch, complication is that NQR data, in contrast 1979, 34A, 220. to the MW, does not yield directions of the principal axes. New double resonance 3. M.H. Palmer, I. Simpson and studies are in progress, in order to R.H. Findlay, Z.Naturforsch, 1981, complete the NQR assignments. Available 36A, 34. data for ammonia (ill), hydrazine (IV) 4. M.L.S. Garcia, J.A.S. Smith, as well as I and II shows significant P.M.G. Bavin and C.R. Ganellin, differences between the microwave (MW) J.Chem.Soc. Perkin, 1983, in press, gas-phase nuclear quadrupole coupling (NQCC) data and that for the condensed 5. M.H. Palmer, F.E. Scott and phases [1]. J.A.S. Smith, Chemical Physics, 1983, 74, 9. In a parallel theoretical approach, groups of H-bonded azoles and related molecules, are being studied at their known crystallographic orientations. The calculations are based upon ab initio studies previously reported for single molecules [2,3]. The change in computed PA magnitudes parallel those observed for the gas-solid change; for example, in imidazole, the previously inferred tensor axis [4] switch for X s and xvv i- computed [5]. For I, II, 1,2,4-triazole (V), tetrazole (VI) and indazole (VII) the effect of H bonding on NQCC in the solid is largely restricted to the =N-H...N sites; at NH there is a numerical decrease (negative shift) in XR (nearly parallel to NH bond) and in positive shift in XTI (local TT-axis) with the tangential (Xf) largely unchanged. The opposite effects occur at the donor N atom. 2Mt Bulletin of Magnetic Resonance CORRELATION BETWEEN ESR DETERMINED BONDING AND STABILITY OF MIXED LIGAND COMPLEXES OF Cu(ll) B.S. Prabhananda Chemical Physics Group, Tata Institute of Fundamental Research, Bombay 400005 In Cu(ll) complexes contributions to REFERENCES g at the metal is related to strengths of covalent o~-bonding between Cu(ll) 1. G. Krishnamoorthy and B.S, Prabha- with near neighbors. The changes in nanda, J. Magn. Res. , 3_0_, 273 (l 978) the next neighbor hyperfine splitting on 2. G. Krishnamoorthy and B.S. Prabha- forming the mixed ligand complex nanda, J. Phys. Chem., 8£, 637 (l 980) Cu(P)(Q), indicates the difference in 3. B.S. Prabhananda, Proc. Indian strengths D-JT , of in plane IT-bond ing Acad.Sci. (in press) with P and Q (l). The stability of 4. L. Pauling, The Nature of Chemical Cu(P)(Q) is reflected in the K asso- Bond, 3rd Ed. Cornell University ciated with the ligand exchange Press,Ithaca, 1960, pp 79-83 reaction: Cu(P) ZCu(P)(Q) K = \Cu(P)(Q)] \Cu(Q)} Cu(btc)(TPA) shows a large K (=270) and a large deviation 8 in the metal hyperfine constant from the average 002 value (2), suggesting a relation for between them (3). Fig.l. KQ vs. Ag ligand pairs: 1. dtc -dSeP, 2. dtp-dtpi, 3. btc -dtpi, K = KQ exp(0. 347 6 ) 4. dtc -TPA, 5. btc -dtp, 6. btc -dSeP, 7. ac. ac -TPA, 8. btc -TPA, 9. ac. ac-«-dtc, Fig. 1 shows dependence of K on £g, 10. dtc -dtp, 11. dtc -dtpi, 12. btc -TPA the difference in g of Cu(P) and Cu(Q). For small £kg, K- depends on EL^ also (3). Behavior shown in fig.l could be seen in several other systems also. This is similar to the dissociation energies of diatomic molecules (4). For Cu(HyL, (Hy = 8-hydroxyquinoline) g = 2.1056. For Cu(Hy)(btc) &g= 0.023 and fig. 1 predicts Kfv4.5. Since a small negative g is associated with btc ligand we expect K to be slightly less than 4.5. The observed Kisr-'Z. 8 Fig. 2. ESR spectrum (a). Simulated (fig. 2). We have also got Kr^O.Ol for spectrum for the high field region with Cu(Hy)(dtc) consistent with the fCu(Hy)2} : \Cu(btc)2"3 : \_Cu(Hy)(btc)] predictions of fig. 1 for Ag= 0.0576. = 40 : 2 : 30 (b). Vol. 5, No. 3A 245 ESR OF IRATI OIL SHALE KEROGEN FROM PARANA BASIN (BRASIL) J.J. Fernandes de Sousa, A.S. Mangrich and N.V.Vugman* Instituto de Fisica da UFRJ-21944-Rio de Janeiro -Brasil The existence of free radicals in kerogens was discovered by Mar_ chand et al in 1968 (1). Since then, several efforts have been ejc pended so as to correlate the beha_ vior of the ESR properties of kero_ gens with both its maturation and its other physical-chemical proper ties. In this way, ESR parameters (li^ newidth, g-value and intensity) have been measured for the first time on a brazilian oil shale, the Permian Irati one, by means of se_ lected samples from the stratigrji phic column CERI-1 from Sao Mateus do Sul, Parana. Comparison of the ESR spectra of samples extracted from different dephts (Fig. 1) and the resulting ones from a standard sample submitted to a temperature- controlled pyrolysis, indicates that the anomaly observed in the behavior with the increasing depth Fig. I: ESR spectra of Irati oil shale kerogem stratigraphy of the ESR signal was promoted by column CERI-I. the presence of a localized heat source at about 29 meters. This result is in agreement with the behavior of the stratigraphic functions measured by Costa Neto et al (2) and is attributed to a diabase intrusion in the sedimentsi ry rocks of the Parana Basin. REFERENCES 1. A.Marchand, P.Libert and A. Com baz, C.R.Acad.Sci.Paris, D.2667 2316(1968) 2. C.Costa Neto, E.G.Furtado, F.J. M.Concha, J.N.Cardoso, and L.P. Quadros, Chem.Geol., 23, 181 (1978) 21*6 Bulletin of Magnetic Resonance TERTIARY STRUCTURE AND STABILITY OF THE EPIDERMAL GROWTH FACTOR Antonio De Marco, Enea Menegatti+ and Mario Guarneri+ Istituto Chimica Macromolecole CNR, Via Bassini 15/A, 20133 Milano, Italy h Istituto di Chimica Farmaceutica dell'Universita, Via Scandiana, 21, 44100 Ferrara, Italy. EGF is a 53 residue polypeptide of multiple biological activities. The pre- sent 1H-NMR investigation is mainly fo- cused on the low-field spectral region (Fig. 1). Homonuclear decoupling, spin- -echo multiplet selection and photo-CIDNP experiments led to full assignment of the resonances from 5 Tyr, 1 His and 2 Trp, jL.ji. the aromatic content of EGF. In par- ticular, the photochemical experiment ga- ve specific attribution of 2,6 and 3,5 doublets in tyrosines and 4-5-6-7 multi- plets in tryptophans. The resonances from two tyrosines appear to be broadened and shifted at high fields (up to 5.9 ppm, Fig. 1), suggesting mutual interaction between the aromatic side chains and the presence of hydrophobic domains in EGF. 7.6 72 6.8 6.4pp 6.0 This is consistent with the presence of Fig. 1. 270 MHz iH-NMR spectrum of 0.2 mM ring current shifted methyl resonances, EGF in D 0, pH 7.9, 45°C: in particular one 6-Ile triplet at 0.65 2 aromatic region. ppm (Fig. 2) . On the other hand, the amide exchange in D_0 solution is considerably faster than that observed for globular proteins of the same size, and most of the aromatic residues are accessible to the flavin dye used to originate spin polarization. The combined evidence sug- gests that EGF possesses a folded struc- ture, but the molecule is rather floppy. Spectra measured at variable pH and tem- perature reveal that the recovery of the native conformation is not quantitative, either from acidic pH, or from high tem- perature unfolding. An extrapolated AG° at 25°C of ca_. 8 Kcal/mol is below the lowest limit of a value quoted in previ- ous investigations (16 ±7 Kcal/mol) based on CD techniques [l] . All this points to a lower stability for EGF than that clai- med to date. 12 1.0 0.8 pprn 0.6 Fig. 2. 270 MHz ^-NMR spectrum of 0.2 mM EGF in D20, pH 7.9, 45°C: methyl region. [1] . Holladay,L.A., Savage Jr., C.R., Cohen, S., and Puett, D. (1976) Biochemistry, 15, 2624-2633. Vol. 5, No. 3A 247 13C AND 2H NMR STUDIES OF LIPIDS FROM HALOBACTERIUM CUTIRUBRUM Irena Ekiel*, G. Dennis Sprott, Harold C. Jarrell and Ian C.P. Smith Division of Biological Sciences, National Research Council of Canada, Ottawa, Canada K1A 0R6 Lipids from ^ cuti rubrum were duced in comparison with those of 13 Z enriched in 13 and H byy growtg h other lipids. Relaxation times on labeled precursors ((acetate, Ti are much shorter than in lipids 2H 0, mevalonate). The 13C NMR without branched chains, sug- 2 gesting slower segmental motion results show that, contrary to 9 what is usually assumed, the pre- (xc ^ 3 x 10" s at 8°C). cursor of the phytanyl lipids- The 2H NMR spectra change very mevalonic acid- is only partially slowly with temperature between derived from acetate. Studies of -10°C and 45°C, arguing against the incorporation of the other the presence of a gel-liquid 13C- and llfC-labeled precursors crystal phase transition over allow specification of the origin this temperature range. of all carbon atoms in mevalonic acid. The 2H NMR spectra of lipids 2 labeled from acetate and H20 show that quadrupolar splittings (<.2O kHz) are significantly re- 248 Bulletin of Magnetic Resonance STERIC INTERACTION BETWEEN THE PERIPHERAL SUBSTITUENTS OF 1O(S) CHLOROPHYLL DERIVATIVES AND ITS CONFORMATIONAL CONSEQUENCES AS REVEALED BY 1H NMR SPECTROSCOPY Paavo H. Hynninen and Simo Lotjonen Departments of Biochemistry and Chemistry, University of Kuopio, P.O.Box 138, SF-7O1O1 Kuopio 10, Finland For the elucidation of the mechanism been obtained. The relatively large A6- of photosynthesis at molecular level,de- values (0.1 to 0.2 ppm) observed for the tailed structural information of chloro- P-1-CH2, P-2-CH, P-3a-CH3 and 10b-CH3 phylls and their derivatives is highly proton signals reveal directly the prox- desirable. To this end, we have recently imity of the C-10 methoxy carbonyl group investigated the stereoelectronic proper- and the olefinic region.of the phytyl ties of 10(S) chlorophyll derivatives by group in the 10(S) derivatives (Fig.1). 1H and ^C NMR spectroscopy1>2, xhe im- In addition, it can judged from the other proved methods3>4 developed for the pre- observed A<5-values that the steric crowd- paration of the 10(S) chlorophyll deri- edness in the periphery of the 10(S) de- vatives have now permitted the detailed rivatives increases steric strain which comparison of their conformations with is relieved by prononunced conformation- those of the corresponding 10(R) deri- al alterations in rings IV and V and to vatives utilizing 1H NMR spectroscopy. a lesser extent also in the whole mole- Starting from the highly purified 10(S) cule. The conformational differences are derivative and following its conversion larger for the magnesium-free epimers to the corresponding 10(R) form by re- than for the chlorophylls. In the former peated 1H NMR spectral measurements in case, they are manifested also by large acetone-dg, reliable values for the dif- A6-values (0.1 to 0.5 ppm) of the pyr- ferences in the chemical shifts (AS) have rolic NH protons. B Fig.1. Structures of 10(R) chlorophyll _a (A) and 10(S) chlorophyll a (B). 3 P.H. Hynninen and G. Sievers, Z. Na- P.H. Hynninen and S. Lotjonen, turforsch. 36b, 1000 (1981). Synthesis (1983). In press. ' S. Lotjonen and P.H. Hynninen, Org. S. Lotjonen and P.H. Hynninen, Magn. Reson. (1983). In press. Synthesis (1983). In press. Vol. 5, No. 3A ESR STUDIES ON THE MEMBRANE LIPID BILAYERS ON A MODERATELY HALOPHILIC BACTERIUM ATSUSHI HYONO, SHIGEKO.KURIYAMA, HISAKO HARA, AND MASAMIKI MASUI Osaka City University Medical School, Abeno-ku, Osaka, 545, Japan A moderately halophilic gram-nega- reaching to the depth of 12 carbon tive bacterium, Pseudomonas halosaecha- atoms of hydrocarbon chain's would be rolytica ATCC 29423, was grown in the rather viscous and the phase at every HP 101 medium containing 0.5-4.5 M NaCl. place in those surface layers changes ESR spin-labels, 5NS, 12NS and 16NS from solid to liquid at the same tem- were labeled on the lipid bilayers of perature, near the growth temperature. intact cells, isolated outer and cyto- IH. The order parameter, S, of 12NS plasmic membranes and liposomes of ex- was sufficiently smaller than that of tractable lipids of this bacterium. 5NS. All order parameters of 5NS, 12NS I. From ESR experiments, order pa- and 16NS varied smoothly as measuring rameter, S, and correlation time, x , temperature was elevated even at the were obtained. Andrade plot: phase transition temperature. It may be concluded that when the phase of 1/T log(T the surface layers changes at the was done according to the equation: growth temperature a large amount of 1/2 latent heat goes in and out though the ln(x /T ' )=Const.+E . (1) variation of order parameter (entropy) Both Andrade plots of 5NS and 12NS in is a little. intact cell membranes, outer and cyto- IV. The anionic phospholipid compo- plasmic membranes and liposomes were sition was far more than 50 % of total all composed of two straight lines with phospholipids of extractable lipids of a break point around the growth temper- this bacterium. Thus, the surface of ature of this bacterium. At this tem- this lipid hilayer would be negatively perature, the solid-to-liquid phase charged and surrounded with positive transition would occur, and from the ion (Na or K ) atmosphere. The elec- tangents of two straight lines the ac- trostatic potential is given by chemi- tivation energies, E . , of rotational cal potential and concentration of micro-viscosity at botn solid and liq- some ion, for example, Na , (subscript, uid states were calculated (15-25 kcal/ m: membrane surface, s: in the solution mol for solid state; 5-10 kcal/mol for far from the surface): liquid state) (1). Though both Andrade plots of 5NS and 12NS had a break point, no break point was observed in Andrade Gibbs equation is given: plot of 16NS and the activation ener- gies were 5-10 kcal/mol, that is, the dE+pdv+Eu.dn.=Tds (3) both surface layers which range over from the polar surface to the depth of In this equation, dv=0 and ds=0, then 12 carbon atoms of.hydrocarbon chains the latent heat would be used for the of lipid bilayers change their phases variation of internal energy, dE, and at the growth temperature, whereas the dn. means the increment of ion, i (Na ) interior layer is always in liquid This thermodynamics cam be applied on state. biomembrane homeoviscous adaptation. H. The correlation time, T , of REFERENCES 12NS in the lipid bilayers of all mem- branes, intact cells, outer and cyto- 1. A. Hyono, et at. , J. Biochem. plasmic membranes and liposomes, was (Tokyo) 88, 1267, 1980. almost equal to that of 5NS. This means that both thick surface layers 250 Bulletin of Magnetic Resonance 31P NMR STUDIES OF PHOSPHORYLATED DERIVATIVES OF a-CHYMOTRYPSIN Deborah Kaliick", Dinesh 0. Shah, and David G. Gorenstein Department of Chemistry University of Illinois at Chicago Chicago, Illinois 60680 Phosphorylated derivatives of -4.7 ppm (upfield from 85% H3PO4 or-chymotrypsin have provided important reference). The -4.7 ppm signal is structural and mechanistic information associated with a covalent phosphory- on this enzyme. Thus, the diisopropyl lated species which cannot be removed phosphoryl-ar-chymotrypsin species, in even upon prolonged dialysis. Older which serine-195 is covalently phospho- samples show additional non~dialyzable rylated, has contributed to our under- signals at +.33 and +1.08 ppm probably standing of the important nucleophilic associated with "aging" of the triester role played by the y-oxygen of to ring opened diester phosphorylated serine-195 in the enzymatic mechanism of species. hydrolysis of acyl substrates. Indeed, In order to assign the peak at -4.7 the tetrahedral phosphorylated enzyme ppm, we have synthesized model compounds has been considered a "transition state (3, as well as the equatorial derivative analog" of the reaction. The 31P NMR of 3). To compare the phosphorylated spectra of the diisopropyl phos- enzyme 2_ with axial and equatorial ester phoryl-a—chymotrypsin, the phenyl phos- model compounds under similar conditions phoryl-a—chymotrypsin, and 2~oxo- with minimal environmental perturbation trans-5,6-tetramethylene-l,3,2- di~ of the 31P chemical shift, we compared oxaphosphorinanyl-or-chymotrypsin provide the spectra in 8M urea, 20% D2O, pH 7.0 direct information on the structures of (denaturing conditions for the enzyme these complexes as well as the stereo- complex). The 31P signal for the phos- chemistry of the phosphorylation reac- phorylated enzyme species shifts tion. slightly to -4.65 ppm under these condi- The reaction of a-chymotrypsin with tions (Figure 1) and the 31P chemical the axial phosphorinane triester, la, shifts for 3 (axial) and 3 (equatorial) [2-(2,4-di-nitro-phenoxy)-2-oxo-trans~5, are -5.8 and -4.7. ppm respectively. 6-tetramethylene-l,3,2-dioxaphosphor- inane] yields a stable phosphorylated enzyme derivative, 2: Figure 1. 31P [XH] NMR of Denatured enzyme complex, 2, in 8M urea, 32.4 MHz. 1-" R = 2,4-DNP 3: R = CH2CH(CO2CH3) NHCBZ Clearly, the 31P signal of the phos- Phosphorus-31 NMR spectroscopy has phorylated enzyme corresponds most been used to characterize the phosphory- closely with that of the equatorial lated enzyme intermediate 2, and, in ester model serine ester 3_. We can rea- particular, to determine the stereochem- sonably conclude, therefore, that the istry of the enzymatic reaction. A single displacement, phosphorylation freshly prepared sample of 2 shows only reaction has proceeded with 100% inver- a single phosphate triester signal at sion of configuration. Vol. 5, No. 251 ELECTRON PARAMAGNETIC RESONANCE STUDIES ON SPIN-LABELLED BOVINE BRAIN HEXOKINASE Alka Mehta, Gotam K. Jarori and Umakant W. Kenkare Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400005,India Bovine brain hexokinase catalyses minima and high field maxima remains transfer of Y"-phosphoryl group of ATP unaltered indicating the easy accessi- to glucose. Activity of this enzyme is bility of solvent to the label. modulated by various ligands viz. Pi, Addition of Mg(ll) (SOOjuM) has no ADP, and Glc-6-P. Disposition of effect on the spectral characteristics these ligand binding sites on the of spin-labelled enzyme. However, the enzyme has been far from clear (l). binding of Mn(ll) leads to reduction in Hexokinase binds one Mn(ll) tightly (2) the spectral intensity. The binding which is being used as a reference constant of Mn(ll) with the spin- point to map ligand binding sites using labelled enzyme derived from the NMR relaxation methods (3). This titration of Mn(ll) with the labelled study has been undertaken to introduce enzyme is 35 ±, 7jaM. The maximum another relaxation probe on enzyme reduction in spectral intensity of spin- for ligand site mapping. label due to dipole-dipole interaction Under suitable conditions hexoki- with Mn(ll) is 23%. This has been used nase is reacted with 3-(2-iodoaceta- to determine the distance between two mido)-2,2, 5, 5-tetramethyl-l-pyrro- interacting electron spins. Using lidinyloxyl which leads to incorpora- Leigh's theory (5) and a value of tion of 1.2 + 0.2 moles spin label/mole 2. 2 nSec for electron spin lattice enzyme without any loss of enzyme relaxation time of enzyme bound activity. Fig. 1 shows the EPR spectra Mn(ll) (2), the distance obtained bet- of free and enzyme bound spin label. ween spin-label and Mn(n) on the The rotational correlation time ("£f ) enzyme is 20.4 + 0.2 A. derived from this spectrum is 4.2 + 2. 1 nSec (4) which is much shorter REFERENCES than overall "X^-oi the enzyme calcula- 1. Wilson, J. E. in "Current Topics in ted according to Stokes-Einstein law cellular regulation" vol. 16, Aca- (25 nSec). Splitting between low field demic Press, pi (1980). 2. Jarori, G.K., Kasturi, S. R. and Kenkare, U. W., Arch. Biochem. Biophys. 211, 258 (1981). 3. Mildvan, A.S. and Gupta, R.K. , in "Methods in Enzymol. " vol. XLDC, part G, p 322 (1978). 4. Jones, R. , Dwek, R. A. and Walker, I, O., Eur. J. Biochem. 34, 28 (1973). 5. Leigh, J.S., J. Chem. Phys. 52, 33fiO 33TO SMO 3390 3400 MK> Gora 2608 (1970). Fig. 1. EPR spectra of free and enzy- me bound spin-lab el at 9.1 GHz and 18°C 252 Bulletin of Magnetic Resonance 31P NMR OF ETHIDIUM ION COMPLEXES WITH RNA MODEL SYSTEMS AND tRNAPhe Kofen Lai," Evelyn M. Goldfield, and David G. Gorenstein Department of Chemistry University of Illinois at Chicago Chicago, Illinois 60680 I. INTRODUCTION tion between drugs and nucleic acids produces only small upfield 31P shifts. 31P NMR spectroscopy can monitor the This also provides additional support "helix-coil" transitions in nucleic for our hypothesis that 31P shifts are acids. A large (.7-1.3 ppm) downfield sensitive probes of phosphate ester con- shift for a wide structural range of formation (2). The downfield drug/helix nucleic acids was observed upon raising peak accounts for ~30%-46% of the inte- the temperature. At low temperature the grated intensity in various molar ratio nucleic acids will exist largely in a of drugs. At 81 MHz and low tempera- double or single helical conformation ture, the poly A* oligo U»Et and soni- with the phosphate ester predominantly cated poly A»poly U«Et systems are in the gauche, gauche (g,g) conforma- clearly in slow chemical exchange on the tion, while at higher temperature the NMR time scale. nucleic acids will largely exist in ran- dom coil unstacked conformations with the phosphate ester in an increased pro- portion of nongauche (g,t) conformations (1). 31P NMR spectroscopy has also proven useful in providing structural and dynamic information on transfer ribonucleic acid (tRNA). (2) 4 2 0-2 -4 We examine the binding of ethidium Fig. 1. 31P NMR spectra of sonicated ion (Et) to poly A»oligo U, sonicated poly A* poly U (Bottom) and poly A* poly poly A»poly U, and to tRNAPhe. 31P U»Et (1:1:3) (Top). NMR provides a convenient monitor of the phosphate ester conformational change In tRNAiPh1 e•Et complex, the Et occurring upon binding of drugs to lodges itself in the tertiary pocket. 31 nucleic acids, P chemical shifts can The most striking effect of the addition potentially be used to determine the of Et on the 31P spectrum is the major type of binding to the nucleic acids broadening of the upfield scattered (e.g. intercalation vs electrostatic peaks which have been associated with binding.) 31P NMR can also be used to tertiary interactions (1). determine the degree of stabilization of the double helix in the nucleic acid REFERENCES systems by the drug. (1) D. G. Gorenstein, Ann. Rev. Bio~ II. RESULTS AND DISCUSSION phys. and Bioeng. H), 355 (1981). (2) D. G. Gorenstein and E. M. Gold- In the poly A«oligo U«Et complex and field, In "P-31 NMR: Principles and sonicated poly A* poly U*Et complex, a Applications" (D. G. Gorenstein, new peak about 2.0 ppm downfield from Ed.) Academic Press, New York, the double helix peak appears. (Fig. 1). 1983. We assign this peak to phosphates per- (3) D. G. Gorenstein, B. A. Luxon, E. turbed by ethidium ion (3). The chemi- M. Goldfield, K. Lai, and D. cal shift of this peak is consistent Vegeais, Biochemistry 21, 580 with the intercalation mode of binding, (1982). since the purely electrostatic associa- Vol. 5, No, 3A 253 APPLICATION OF LONG RANGE PROTON DECOUPLING TECHNIQUE TO THE ASSIGNMENT OF THE QUATERNARY CARBON SIGNALS IN THE C-13 NMR SPECTRA OF CHLOROPHYLLS AND RELATED PORPHYRINS Simo Lotjonen and Paavo H, Hynninen Departments of Chemistry and Biochemistry, University of Kuopio, P.O.Box 138, SF-7O1O1 Kuopio 10, Finland The assignment of the C-13 NMR sig- We now report, using chlorophyll a nals of the quaternary macrocyclic car- and pheophytin a as model compounds, bons of chlorophylls and related unsym- that the long-range selective proton metrically substituted porphyrins has decoupling with low power irradiation proved difficult^>2. ihe chemical (LSPD) is the most efficient assign- shifts of these carbons are generally ment technique for the quaternary car- closely spaced and depend strongly on bon signals in the C-13 NMR spectra of solvent, concentration and the substi- the substituted chlorins. In this tech- tution in the periphery of the molecule. nique the long-range C-H couplings are For these reasons, the chemical shift selectively eliminated by weak single comparison is an uncertain method for frequency H-1 irradiation^^. The ap- the assignment. However, the assign- plication of LSPD requires that the ment of these carbons is highly desir- H-1 NMR spectrum of the compound is able, as their chemical shifts contain assigned and that the proton to be ir- information on the TT system of the radiated is not strongly coupled to macrocycle which is an essential chemi- other protons. These requirements are cal property of the porphyrins. fulfilled for most substituted chlo- rins. For example, in the H-1 NMR spectra of our model compounds (Fig.1) narrow, well-defined singlets are ob- served for the a-, g- and 6-methine bridge protons, C-10 proton and la-, 3a- and 5a-methyl protons. The selec- tive low-power irradiation of these H,C protons eliminates only those long- range C-H couplings in which the ir- radiated proton is involved. With the aid of the information obtained by se- lective low-power irradiation of these protons, the assignments for most qua- CH, ternary carbon signals of the model compounds are achieved. References \ioa CO2 Phytyl OCH3 1. S.G. Boxer, G.L. Closs and J.J. Katz, 7e 10b J. Am. Chem. Soc. 96^, 7058 (1974). 2. S. Lotjonen and P.H. Hynninen, Org. Fig. 1. The structure of pheophytin a. Magn. Reson. J^, 304 (1981). Chlorophyll a has Mg instead of two 3. S. Takauchi, J. Uzawa and H. Yone- N-H protons. hara, Tetrahedron Lett. 2943 (1977). 4. K. Sakata, J. Uzawa and A. Sakurai, Org. Magn. Reson. 10, 230 (1977). Bulletin of Magnetic Resonance EPR STUDIES ON Ni(II) AND Cu(II) RECONSTITUTED HEMOGLOBINS P.T. Manoharan, Kenneth Alston and Joseph M. Rifkind Laboratory of Cellular & Molecular Biology, NIH/NIA, Gerontology Research Center, Baltimore, Maryland 21224 The binding of Cu(II) to human hemo- TABLE I globinsl FeHb occurs at two sites: (1) EPR SPIN HAMILTONIAN PARAMETERS FOR Cu(II) a high affinity site involving four ni- IN FeHb-Cu(II) AND NiHb-Cu(II) COMPLEXES trogens far removed from the heme and High Affinity Low Affinity not involved in the oxidation of heme NiHb FeHb • NiHb FeHb and (2) a low-affinity site closer to g,. 2.321 2.208 2.237 2.27 the proximal side of the heme and re- g! _ 2.0555 2.054 2.05 2.057 sponsible for the oxidation of Fe(II). A7,(cm_rA7(cmr) 0.0155 0.0201 0.0219 0.0182 Reconstituted Ni(II) and Cu(II) hemoglo- A^ ) ^0.0020 bins do not bind oxygen, and are similar in many respects to T-state deoxyhemo- heme it could reflect the difference be- globin. We have studied the EPR of tween the coordinations of Ni and Fe in these reconstituted hemoglobins and these hemoglobins; furthermore, the dia- their interactions with Cu(II). magnetic property of NiHb may imply weak NiHb was found to be diamagnetic. or no binding of the proximal histidine The EPR spin Hamiltonian parameters ob- to Ni(II) making it available for binding tained for NiHb-Cu(II) are compared with with Cu(II). those for FeHb-Cu(II)2 in Table I. A strong exchange interaction between These data indicate that there are also the higher affinity Cu(II) bound to the two protein sites for Cu(II) binding but protein and the heme copper confirm the that the high affinity FeHb site has be- location of this site near the heme. come the low affinity NiHb site and vice This shows up by the progressive reduction versa. While the g- and A^u tensors for in the intensity of EPR signals due to the high affinity FeHb site remain simi- CuHb and by the failure to detect the Cu lar, the superhyperfine splitting ob- bound to the protein on the increased ad- served in the gi region for this site dition of external Cu2+. Furthermore, the are only poorly resolved in NiHb. We ESR parameters for CuHb (gjj = 2.203; A(j = 0.0185 cm~l) as compared with CuMb (g|| = attribute the differences in the proper- 1 ties associated with this site far re- 2.223; A|| = 0.0193 cm" ) having a fifth coordination and the complexes such as moved from Ni to the change in confor- 1 mation between the liganded (R) and un- CuPPDME (g,j = 2.1979; A,| = 0.0204 cm" ) liganded (T) structures. It must be no- in chloroform reflect a considerable weak- ted that all previous binding and ESR ening of fifth coordination due to the studies were done on met, oxy or CO FeHb proximal histidine in CuHb. It is known in the R-state while NiHb is considered that Cu in methemoglobin or oxyhemoglobin to be in the T-state. is > 10 A from Fe and that there is no ex- change interaction between them. This The high affinity site of NiHb seems supports the idea that there are changes to be the same as the low affinity site in the coordination of Cu(II) bound to the of FeHb responsible for oxidation of protein in these reconstituted hemoglobins hemoglobin. However, a comparison of perhaps due to the weakening of the fifth the EPR parameters show that there is coordination by the proximal histidine, an increase in gj| and a decrease in A|j which permits the coordination of the non- values in NiHb. The deviations may in- porphyrin Cu(II) to the proximal histidine dicate a weaker interaction with the bringing it to within 5A of the porphyrin ligands in this site and Cu(II) in T- metal. state NiHb than for the corresponding site in R-state FeHb. These departures References in the ESR parameters for this site in 1. J.M. Rifkind, Biochemistry 18^ 3860 NiHb may also imply a weak interaction (1979) and references therein. with the proximal histidine. Since 2. T. Bemski, T. Arends and G. Blanc, this site is relatively close to the Biochem. Biophys. Res. Commun. _3_5, 599 (1969). Vol. 5. No. 3A 255 EFFECTS OF THERMAL BLEACHING ON IRRADIATE! HUMAN TOOTH ENAMEL - AN ESR STUDY T.R. Kesavan and V.S. Murty Electron Spin Resonance Laboratory, Department of Physics Indian Institute of Technology, Madras 600 036, INDIA. Human tooth enamel consists main- are formed only after heating the ly inorganic matter such as calcium irradiated sample. They are proba- hydroxyapatite (CaHA) and impurities bly due to a radical which is like carbonate etc. Water and organic formed after rearrangment in radi- matter are also present in small ation damaged organic matter such quantities. In this study we report as collagen present in the human the formation of new centres obtain- tooth enamel. A similar centre in ed after thermally bleaching the ir- the case of irradiated cow hide is radiated powder. By process of eli- already reported by Kipnis et al(2). mination they are tentatively assig- To check whether these lines ned to the radiation damage of the are due to the small percentage of small quantity of organic matter s organic matter present in the enamel, such as collagen present in the human both dry and wet ashing experiments^) tooth enamel. are done and the sample is irradia- The enamel chips are cut from the ted subsequently. The thermal cycl- human tooth using diamond saw mill ing experiments are also exactly and powdered. The Y"-irrac*iation followed. The ESR spectra recorded (0.2 M rad/hr for 6 hours) is done on these samples do not show the at RT (300K) in a gamma cell follow- two line pattern (which is present ed by ESR record in X-band on AEG in the ESR of untreated sample) 20 X/Q T spectrometer which has a thereby adding strength to our sug- proton probe for magnetic field ca- gestion. libration. DPPH is used as g-marker. Further experiments on enamel The temperature variation experi- chips obtained from different sour- ments are done using AEG VT acces- ces such as (a) healthy adult tooth sory. At each temperature the sample (b) caries sensitive adult tooth is kept for atleast 15 min. before (c) healthy deciduous tooth (d) recording ESR. It is found that the caries sensitive deciduous tooth unirradiated enamel powder does not and (e) fluorosis affected teeth are show any ESR signal. in progress to understand more about The RT ESR spectrum shows signals the crystalline arrangment of CaHA due to radicals such as C03 and and its role in the attack or resis- perturbed 0~ centre (1) but other tance of the diseases. reported centres are not seen. Heating the sample to 430K followed REFERENCES by ESR recording at this temperature show two additional lines with weak (1) M.T. Kay, R.A. Young and A.S. intensity seperated by 4.32mT and Posner, Nature 204, 1050 (1964). centred on g=2.0038 are observed (2) A.B. Kipnis, O.A. Azizova, P.I. and remain till 580K. These signals Levenko, I.G. Shifrin and E.M. still appear on bringing back to RT Sheksheev, Radio Biology XII(3), from 54OK but vanish if heated 80 (1972). beyond 550K. To check if these lines are due to heating alone, p^irolysis (3) G.N. Jenkins, The physiology experiments are done in the above and Biochemistry of the mouth temperature range but only the IV edn., Blackwell Scientific strong Cog centres could be seen. publications, England 59(1978). UV photolysis gave the same centre Co3"" but with very much reduced intensity and stability. Therefore it is confirmed that these two lines 256 Bulletin of Magnetic Resonance B-Z TRANSITION OF d(m5C-G-C-G-m5C-G) BY 1H-NMR SPECTROSCOPY J.M. Neumann--, J. Taboury--', T. Huynh-Dinh**, J. Igolen** and S. Tran Dinh-- -'•Service de Biophysique, CEN Saclay, 91191 Gif sur Yvette cedex, France -'--Unite de Chimie Organique, Institut Pasteur, 75724 Paris cedex 15, France Introduction The B-Z DNA transi- 47 kcal/mole for the Z->B and 39 tion has been investigated extensively kcal/mole for the B-»Z reaction. in the last five years by various spec- The above results indicate that the troscopic techniques. However, although Z double helix is directly obtained frequent guesses were made concerning from the B duplex without passing the mechanism of • the B-Z transition, through the single stranded form as an very little information has been availa- intermediate state. The B-Z transition ble until now. In the present communica- is only possible when the Watson-Crick tion, the B and Z forms of the hexamer hydrogen bonds between the C-G base d(m C-G-C-G-m C-G) and the mechanism pairs are firmly maintained, otherwise governing the B-Z transition were stu- the passage from B to Z fails and the died in solution by 500 MHz H-NMR. B-helix coil dissociation takes place Results and Discussion : In a 0.1 M instead. This explains why alternating NaCl solution, only the B form is detec- d(T-A)n oligomers cannot give rise to ted whereas the Z form is predominant the Z conformation since there are on- in 3 M NaCl. In the presence of Z M ly two hydrogen bonds in a A-T base NaCl, for t>60°C each proton of d(m C- pair instead of the three present in G-C-G-m C-G) gives rise to a single re- G-C. By contrast a salt-induced B-Z sonance signal, the chemical shift of transition occurs in the case of the which is similar to that obtained with hexanucleotide consisting of thymidine a 0.1 M NaCl solution. By contrast for and 2-aminodeoxyadenosine, d(T-2-amino t<50°C, two resonances were observed for each proton as indicated in fig. 1 for the base protons. The additional 5 s signals were attributed to the Z form d-(m C-6-C-G-m C-G) ?M»;aCl c-6 on the basis of the NOE measurements : on saturation of the G., resonances, a negative NOE of 53+2 % was observed on the G resonances. The Z form is only detectable when the coil form is practi- cally absent. Lowering the temperature has the effect of increasing the Z pro- portion to the detriment of the B fraction. The Z proportion is about 25 % at 50 °C and increases to 61 % at 17°C. The B-Z exchange is slow below 50°C and becomes intermediate or fast in the 55-80°C temperature interval. Proton linewidth measurements under various experimental conditions show that the Z form exchange only with B while the latter also exchanges with the coil form (C) : Z+B+C. The enthalpy value is about 8+_1 Kcal/mole for the B-Z transition and 8.0 7.8 7.6 7.4 7.7 pprn 40+2 kcal/mole for the B-C dissocia- tion. The Z form of d(m C-G-C-G-m C-G) Fig. 1- Temperature effect on 50Q MHz is energetically more stable than the B H-NMR spectra of d(m C-G-C-G-m C-G) form : the activation energy is about base protons in 2 M NaCl solution. Vol. 5, No. Ilk 257 CONFIGURATIONAL AND CONFORMATIONAL STUDIES OF SOME 3-ALKYL FENTANYL DERIVATIVES BY 0-15 AND PHOTON N.M.R. SPECTROSCOPY. F.O. OGUBGBAMILA' Department of Pharmaceutical Chemistry, University of Ife,. lie- Ife, Nigeria. A.F. GAS* School of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, U.K. The stereo-structure-activity studies (0-5 in the 3-alkyl analogues) is shiel- in the C-alkyl substituted reversed este- ded in the cis-isomer (3-4 ppn» upfield) rs of Pethidine has demonstrated the dra- through a y-gauche interaction, whereas matic influence of configuration on anal- it is little affected by the equatorial- gesic potency of this class of narcotic ly oriented alkyl substituent in the tr- H Fig.l. Part of the 220 MH* spectrum of cis-3-propyl fentanyl. Ph( COEt )N R analgesics (l). The isomeric 3-methyl analogues of Fentanyl also differ remark- ably in their analgesic potency (2). Hence the need for an unequivocal method H ans-isomer. The C-4 chemical shift is B Fig. 2. Part of the 100 MHz spectrum of trans-3-propyl fentanyl, II of establishing the configuration and identity of the different isomeric forms. K.m.r. spectroscopy offers a very con- venient and unequivocal method for establ- ishing the configuration and preferred so- lute conformation of C—alkyl substituted Fentanyl analogues. The characteristics of the C-4 methine proton in the cis-(l) and trans-(Il) piperidine chair isomers and their intermediate conformations are diagnostic. The emphasis is not only on the value of the vicinal coupling constan- moved 3-5 ppm upfield in the trans-isom- ts, but also on the actual appearance of er as a result of the steric compression the spectrum. In I, the C-4 proton appea- from the equatorial 3-alkyl substituent. rs as a doublet of triplets (Fig. l) as a These features can also be used to dist- result of a large coupling to one axial inguish intermediate conformations. proton to give a doublet, each signal of which is again split into three by the sm- REFERENCES. aller coupling to two equatorial protons. 1. A.F. Casy, Progr. Drug Res., 22, 149, In the trans-isomer, the C-4 proton appea- 1978. rs as a triplet of doublets (Fig.2, 4-H 2. W.F.M. van Bever, C.J.E. Niemegeers, is coupled to two axial and one equatorial and P.A.J. Janssen, J. Med. Chem., 17» protons). 1047, 1947. The y-carbon to the alkyl substituent 258 Bulletin of Magnetic Resonance 13C-NMR EVIDENCE FOR THE PATHWAY OF CHLOROPHYLL BIOSYNTHESIS IN GREEN ALGA AND PHOTOSYNTHETIC BACTERIA Tamiko Oh-hama, Haruo Seto and Shigetoh Miyachi Institute of Applied Microbiology, University of Tokyo, Bunkyo-ku Tokyo, 113, Japan 13 The first precursor specific to tet- In both organisms C-2 of [ 2- C ]- rapyrrole formation is 5-aminolevulin- glycine was specifically incorporated ic acid (ALA) which can be formed into methoxyl carbon (10b) of methox- either by condensation of glycine and ycarbonyl group attached to isocyclic succinyl-CoA catalyzed by ALA synthase ring of chlorophyll a and bacterio- or from the entire carbon skeleton of chlorophyll a, showing that C-2 of glutamate or 2-oxoglutarate (^ ~ glycine was used for methylation of pathway (1)). In the former pathway, magnesium protoporphyrin. C-5 of ALA is derived from C-2 of glycine, while it is derived from C-l of glutamate or 2-oxoglutarate in the C -pathway. Carbon C-5 of eight molecules of ALA has been reported to be incorporated into four methine bridge carbons (a, 3 , 1 and S ) and four a -pyrrolic carbons (C-12, 14, 16 and 17) of chlorophyll as shown in Fig. 1 by closed circles. In this work C-NMR spectral anal- ysis was performed in chlorophylls a and b formed in a green alga Scenedesmus obliquus and bacterio- 7c CO2Phy chlorophyll a in a photosynthetic Fig. 1. The numbering system for bacterium Rhodopseudomonas spheroides chlorophyll a. Atoms denoted by in the presence of [ 1- C ]-glutamate closed circles (•) are derived from or [2- C]-glycine ^ In Scenedesmus C-5 of ALA. cells C-l of [ 1- C ]-glutamate was preferentially incorporated into the References eight carbons described above (2,3) 1. Beale.SI (1978) Ann. Rev. Plant according to early assignment of Physiol. 29, 95. chlorophylls a and b (4,5,6), while no 2. Oh-hama,T. Seto.H, Otake.N and enrichment of the carbons occurred Miyachi,S. (1982) Biochem. Biophys. with [2- C J-glycine. Reverse was the Res. Comm. 105, 647. case irL photosynthetic bacteria: C-2 3. Oh-hama,T, Seto.H, Otake.N and of [2- C]-glycine was specifically Miyachi,S. (1983) FEBS Lett. 153, incorporated into the eight carbons 404. derived from C-5 of ALA in bacterio- 4. Boxer,SG, Closs,GL and Katz.JJ chlorophyll a although the assignment (1974) J. Am. Chem. Soc. 96, 7058 for C-14, 16 and 17 made by Brereton 5. Lotjonen,S and Hynninen,PV (1981) and Sanders (7) did not fit to our Org. Magn. Reson. 16, 304. data. Thus C-NMR spectral analysis 6. Risch.N and Brockmann.H (1983) proved that ALA is produced by ALA Tetrahed. Lett. 24, 173. synthase in R_^ spheroides, while it is 7. Brereton,RG and Sanders,JKM (1983) produced via C -pathway in S. obliquus. J. Chem. Soc. Perkin Trans. I, 435. b Vol. 5, No. 3A 259 FLUORINE NMR SPECTRA OF 'TRANSITION-STATE ANALOGUE' COMPLEXES OF-N-ACYL-P-FLUOROPHENYLALANINALS AND a-CHYMOTRYPSIN Dinesh 0. Shah and David G. Gorenstein Department of Chemistry University of Illinois at Chicago Chicago, Illinois 60680 I. INTRODUCTION where the a-chymotrypsin has a maximum rate of activity. Also line widths at Enzymes are predicted to bind tran- half height and chemical shifts of the sition-state structures more tightly hemiacetal X*F signal were found to be than ground-state structures and hence a pH dependent, again with maximal effects "transition- state analogue", a molecule occurring around pH 8.0. This is that resembles the transition state, attributed to an increase in the should have a higher affinity for the exchange rate between non-covalent enzyme than substrate or product ana- Michaelis complex and the covalent logue structures. enzyme complex. Peptide aldehydes related to sub- The D- and L-enantiomers of the hyd- strates have proven to be potent inhib- rate of the N-acetyl aldehyde give sepa- itors of serine proteases (D. G. Goren- rate fluorine NMR signals which were stein and D. 0. Shah, Biochemistry 21, also found to be pH dependent. At pH 4679 (1982); ibid., 1983, in press) and 8.0 clear resolution of the D- and it has been suggested that the tighter L-hydrate signals are obtained in the binding of the aldehydes derives from proton coupled spectrum, suggesting that stabilization of a hemiacetal tetrahe- rapid chemical exchange occurs between dral adduct (resembling the transition the L-aldehyde-a-chymotrypsin complex state) formed between the enzyme active and the free hydrate at pH 8.0. The site serine and the aldehyde carbonyl. enzyme-bound inhibitor fluorine signals Evidence in support of the "tran- disappear upon proton decoupling due to sition state analogue," hemiacetal a negative nuclear overhauser effect structure, however, has largely been (-100%). Upon decoupling of protons, indirect. In the following we show that the L hydrate and free aldehyde fluorine *'F NMR can provide direct support for signals are reduced in intensity rela- this structure. tive to that of the D hydrate signal in the racematic aldehyde complex. This is II. RESULTS AND DISCUSSION attributed to a saturation transfer of the heteronuclear nuclear Overhauser Fluorine NMR spectra of N~acetyl-D,L- effect. p-fluorophenylalaninal in the presence Separate preparation of pure N~ace- of a-chymotrypsin show separate signals tyl-D-p-fluorophenylalaninal as well as for the hemiacetal complex, (-33.8 ppm) the L-enantiomer and X'F NMR study of the bound aldehyde, (-37.2 ppm) the free their binding to a-chymotrypsin provided aldehyde, (-37.8 ppm) and free hydrate confirmation of the signals identified (-38.4 ppm). N-Benzoyl-D,L-p- in the spectra of the D,L-racemate fluorophenylalaninal fluorine NMR sig- enzyme complex. Only the L-aldehyde nals are also observed for all species forms the tight hemiacetal complex. except the bound aldehyde form in the The 4 ppm downfield shift we observed presence of o-chymotrypsin. The hemi- for formation of the hemiacetal complex acetal formation of the N-acetyl aldeh- is one of the largest protein induced yde with a-chymotrypsin was found to be 1!F shifts observed for a reversibly pH dependent, with a maximum amount of bound inhibitor to Cht. the hemiacetal present around pH 8.0, 260 Bulletin of Magnetic Resonance APPLICATION OF NMR TECHNIQUES TO THE STUDY OF STEREOCHEMICAL CONTROL IN POLYKETIDE ANTIBIOTIC BIOSYNTHESIS Mary M. Sherman*and C. Richard Hutchinson UW-Madison, School of Pharmacy, Madison WI. 53706 The rise of stable isotopes in biosyn- that have been activated for precursor thetic studies has become common, first assembly, or by scrambling of label via because of the availability of high field various metabolic routes. In one case, NMR instruments, and more recently as the (Ref.2) we were able to measure the iso- result of the development of advanced NMR topic enrichment of ^H in Lasalocid A by techniques such as triple resonance, an- means of the Triple Resonance Experiment alysis of isotope shifts, pulsed NMR and (^C^H^H}). In another case, (Ref.3) 2D-NMR. These methods allow an accurate ^H-retention was observed via high field measurement of isotope enrichment at low 2H-NMR and quantitated with high-resolu- levels and thus a means of following tion MS. complex biosynthetic pathways in vivo. In our current work, we are involved We are involved in a broad study of in the study of multiply-labelled precur- the comparative biosynthesis of fatty sors (l3C--*-3C,^H) in an attempt to study acids and polyketide antibiotics. Like various rearrangement mechanisms. The fatty acids, these antibiotics are as- methods already mentioned (triple-reso- sembled by the regular addition of sim- nanance, high-field 2H-NMR, and isotope ple carboxylic acids, presumably via shift analysis) along with various 2D-NMR their malonyl esters, in the biochemical techniques should facilitate our analy- equivalent of the Claisen reaction. Un- sis of these experiments and thus pro- like fatty acids however, this assembly vide further insight into the mechanism involves a variable sequence of the C-2 of carbon chain assembly of the polyke- to C-4 subunits, and yields non-regular tide antibiotics. configurations at the methine and methy- lene centers. By looking at the reten- Ref s. tion of stable isotope labels (13c,l&0, 1. C.R. Hutchinson, M.M. Sherman, J.C. 2H) located in acetate, propionate, suc- Vederas, T.T. Nakashima, JACS, 103, cinate and butyrate precursors during 5953, 1981. their incorporation into the polyether 2. C.R. Hutchinson, M.M. Sherman, A.G. antibiotic, Lasalocid A (fig.l), by Mclnnes, J.A. Walter, J.C. Vederas, Streptomyces lasaliensis, we are able to JACS, 103_, 5956, 1981. propose mechanisms for the carbon chain 3. M.M. Sherman and C.R. Hutchinson, assembly of this antibiotic. unpublished results. Initial experiments followed the re- giochemistry of the incorporation of 13C-18Q labelled precursors into Lasalo- cid A by observing the ot-isotope shift in the -^C-NMR spectra, and from this quantitating the isotopic enrichment from the ratio I(13C-1°O)/I(13C-18O)+I (13C_16O). Subsequent experiments have followed the fate of the C-2 hydrogens of the pre- cursors as a means of studying mechan- isms of stereocontrol during the forma- tion of Lasalocid A. Biosynthetic ex- periments involving isotopic hydrogen labels in whole cell work offer consider- able difficulty due to the loss of label either from exchange with -4l in the media at methylene and methine centers Vol. 5, No. 261 SODIUM-23 NMR STUDIES OF DETERGENT-MEDIATED NA+ TRANSPORT ACROSS LIPID BILAYER MEMBRANES David M. Yarmush and Charles S. Springer, Jr. Department of Chemistry State University of New York at Stony Brook Stony Brook, New York 11794 Detergents are widely used for bio- first order rate constant of chemical manipulation of real and syn- 1.2 xlO^min"1 at 32°C. The temperature thetic membranes. Often, the goal of dependence of this leakage yielded val- these manipulations is the reconstitu- ues of AH* equal to 58.6 kj/mol and tion of a transmembrane transport func- AS* equal to -40eu. tion. However, a concern is the trans- Addition of the detergent dodecyl port which may be induced by the sulfate (DS"1), as the Li* salt, induced detergent itself. To study this, we faster efflux of the Na*. A mole ratio prepared Na*-loaded large unilamellar of DS~/EL equal to 0.183 produced a leak vesicles (LUV) of egg lecithin (EL) by with a pseudo-first order rate constant the dialysis of octyl of 4.9 x at 32°C. The rate 3-D-glucopyranoside from mixed micelles. constant was found to depend on the After LUV formation, most of the outside DS~/EL ratio to almost second order Na* was replaced by Li* in a quick dia- (2.4). The temperaturp e dependence lysis. If the outside solution was then yyielde d values of AH* equaq l to 60.2 made 15 mM in the shift reagent 23 kJ/mol and AS* equal to ~32eu. The Dy(chelidamate)3«", the Na NMR spec- disulfate detergent, 1,12-octadecane trum revealed a splitting of 2.1 ppm disulfate, was even more efficient in between a large peak (Na* inside the inducing Na* efflux. This is due to the LUV) and a small upfield peak (residual lower enthalpy of activation, AH*, of Na* outside the LUV). Monitoring the 47.7 kJ/mol (AS* = -39eu). This time dependence of the spectrum yielded detergent also showed an almost second- the efflux of Na* out of the LUV (ca. order (1.9) dependence on the detergent/ 28mM EL). The natural leak rate has a lipid mole ratio. 262 Bulletin of Magnetic Resonance 13-C NMR CHARACTERIZATION OF GUAYULE RESIN COMPONENTS: GUAYULIN A & GUAYULIN B J Visintainer* and W W Schloman, Jr Goodyear Tire & Rubber Company Research Division Akron, Ohio 44316 Guayule [Parthenium argentatum (Gray)] Because of several sets of closely is a desert shrub found in northern Mex- spaced signals, multiplicities were as- ico and southwestern United States. It signed using the Attached Proton Test contains up to 20% by weight cis-1,4- (APT) technique (5). T] arguments were polyisoprene (1) and is a potential do- used to identify methine and methyl car- mestic source of natural rubber. Market- bons. Assignment of aliphatic carbons ing high value resin byproducts could containing zero or two protons was based significantly reduce guayule rubber man- in part on theoretical calculations, T-|, ufacturing costs. We report here the and model compounds. Calculations for 13-C NMR characterization of two resin C4, C5 and C8 are indicative of the components, guayulins A & B, which are trans/trans configuration. This config- the bicyclogermacren-9-ol (I) esters of uration of structure I is in agreement with that of the parent compound bicyclo- germacrene which was assumed to be in the trans/trans configuration based upon thermal considerations (4). The 13-C spectral lines for guayulins A and B corresponded closely to the peaks observed for I and the references, trans-cinnamic and £-anisic acids, re- spectively. All carbon spectral peaks have been identified. The C8 and C10 12 peaks were the only peaks appreciably changed from the chemical shifts of I, which was to be expected from the pre- Table. Observed 13-C Chemical Shifts sence of the ester group. Carbon PPM Carbon PPM Carbon PPM REFERENCES Cl 15.3 C6 125.2 Cll 20.6 1. Guayule: An Alternative Source of C2 126. C7 128.8 C12 20.3 Natural Rubber, National Academy of C3 136, C8 46.3 C13 16.3 Sciences, Washington, DC (1977). C4 40. C9 72.3 C14 28.6 2. W.Schloman,Jr.,R.Hively,A.Krishen C5 25.1 CIO 35.8 C15 29.0 and A.Andrews, J.Agric. Food Chem., in press. trans-cinnamic acid and £-anisic acid, 3. J.RomOjA.Romo de Vivar,A.Ortega and respectively. Ester origins and purifi- E.Diaz, Rev. Latinoamer. Quim. ]_, 132 cation are described elsewhere (2). The (1970). •H NMR spectra of these compounds (3) 4. K.Nishimura.N.Shinoda and Y.Hirose, have been compared with that of bicyclo- Tetrahedron Letts. 36_, 3097 (1969). germacrene (4), but structural details 5. C.LeCocq and J.-Y.Lallemand, J, Chem. required confirmation by 13-C NMR. Soc. Chem. Commun., 150 (1981). Chemical shift data of I in CDClo confirm the presence of 15 carbon atoms. Contribution Number 648 from The Olefinic carbons and C9 were assigned Goodyear Tire & Rubber Company. using additivity parameters derived for this study from linear olefinic alcohols. Vol. 5, No. 263 3-ENDORPHIN: KINETICS OF INTERCONVERSION AMONG DIFFERENT FORMS IN AQUEOUS SOLUTION. Lucia Zetta Istituto di Chimica delle Macromolecole, CNR, Via E. Bassini 15/A 20133 Milano, Italy Although previous NMR and CD studies e-Met on B-endorphin indicated that the mole- cule adopts a predominantly random con- formation in aqueous solution, by vary- ing experimental parameters, such as pH and temperature, it was possible to in- duce the appearance of several, slightly different species. The present investi- gation is focussed on two of such forms (C, and C«) , slowly exchanging with the A native structure (N) , after freezing and subsequent defrosting of a sample of ca- mel 3-endorphin in water. The time cour- se of the relative concentration was followed on a number of selected reso- nances from the different forms. In par- ticular, the resonances of the H-2 and H-4 in His-27 (Fig.l) and of the methyl protons in Ala-26 were used as probes for the disappearing species C, , whereas the signals from the 6 and e protons in Tyr-1 (Fig.l) and from the methyl protons inThr-6 and Met-5 (Fig.l) monitored the growth of C_ . The latter phenomenon oc- curs less rapidly than the disappearance of C, . The kinetics of interconversion among the different isomers is much slow- er than those reported for the blue shift- ing at 286 nm observed during thermolysin digestion of camel 3 -endorphin, and for cis-trans proline isomerization in model compounds [l,2] . Both C,and C~ species also appear during pH-titration of camel 8-endorphin at pH 8, as shown by the reso- nances from the 6 and e protons in Tyr-1 and the methyl protons from Ala-26. The relative intensity of the latter signals changes in time with a slow kinetics, which is not appreciably affected by 7.8 further raising the pH up to 12. As pre- 7.4 ppm 7.0 viously observed for native 6-endorphin F [3], photo-CIDNP experiments show that in J.. 270 MHz H-NMR spectrum of 6 mM both C-^ and C2 conformations Tyr-1 and camel g-endorphin in D2O at 30°C: His-27 are accessible to the flavin dye aromatic region and methionyl used to generate spin polarization. S-CH3 resonances. Uj P.Nicolas, T.A. Bawley, L.Graz and C.H.Li (1981)Proc.Natl.Acad.Sci.USA_7^, 7290. \2~] C.Gratwohl and K.Wuthrich (1981) Biopolymers ^0, 2623. [3JL.Zetta, R.Kaptein and P.J.Hore (1982) FEBS LeTt. 145, 277. 261* Bulletin of Magnetic Resonance NMR STUDIES ON THE MECHANISM OF WATER DIFFUSION THROUGH HUMAN ERYTHROCYTE MEMBRANES Gh. Benga, 0. Popescu, Ross P. Holmes* and V.I. Pop Dept. Cell Biology, Fac. Medicine, Medical and Pharmaceutical Institute Cluj-Napoca, Cluj-Napoca, Roumania, and Burnsides Research Lab., Univ. of Illinois, Urbana-Champaign, USA Previous work in this group has dem- affect water diffusion did not onstrated the usefulness of a NMR tech- hamper the inhibitory action of mer- nique for the study of water exchange curials. The NMR method appears (WE) through human erythrocyte mem- a useful tool for studying changes branes in normal and pathological sub- in water diffusion in erythrocyte jects (1). The temperature and pH ef- membranes following various mani- fects on WE indicated the conforma- pulations of membranes aimed at tional changes of proteins and coopera- locating the water channel. tive effects are implicated in the mechanism of this transport process (2). Subsequent studies examined the effects of chemical modifiers of erythrocyte membranes on the WE. It was found that only SH-reagents, such as p-chloromercur- ibenzene sulfonate (PCMBS) and fluores- ceinmercuricacetate (FMA) significantly inhibited WE. Moreover, the inhibition 1. V.V. Morariu and Gh. Benga. by PCMBS was fully reversed by cysteine Biochim. Biophys. Acta 469:301 while that induced by FMA was irrever- (1977). sible (3). Binding studies with ^3Hg PCMBS and a variety of polyacrylamide 2. V.V. Morariu, V.I. Pop, 0. gel electrophoresis techniques, followed Popescu, and Gh. Benga. J. Memb. by autoradiography or counting of ra- Biol. 62^:1 (1981). dioactivity in different bands, have identified the proteins which bind 3. Gh. Benga, V.I. Pop, M. Ionescu, PCMBS in human erythrocyte membranes. R.P. Holmes, and 0. Popescu. Cell It is suggested that these proteins Biol. Int. Rep. 6^:775 (1982). constitute the channel for water dif- fusion through erythrocyte membranes. The changes in water diffusion across human erythrocyte membranes following exposure to various inhibitors and pro- teolytic enzymes have been studied on isolated erythrocytes suspended in isotonic buffered solutions. It was found that mercurials including mersa- lyl, were the only sulfhydryl reacting reagents that were efficient inhibitors. Other reagents, including the sulfhy- dryl reagent DTNB, phloretin, or H-DIDS, the specific inhibitor of the anion transport system in erythrocyte membranes, did not appear to inhibit significantly diffusional permeability. No changes in water diffusion were no- ticed after trypsinization. Chemical manipulations of membranes that did not Vol. 5, No. Ilk 265 METABOLIC ASPECTS OF LIVER REGENERATION IN RATS. C.A. Boicelli ^*' and A.M. Giuliani CNR, Istituto di Anatomia Umana Normale, Universita di Bologna (Italy) CNR, Area del la Ricerca; CP 10 - 00016 Monterotondo Stazione (Italy) Hepatic regeneration, induced by sur- The level of certain metabolites also gical removal of 70% of the organ, re- shows marked modifications in the regene presents a good example of modified rating liver tissue: triglycerides cont metabolism to be followed by NMR. The ent increases after surgery to reach a rapidly dividing cells of regenerating maximum at _ca_. 36 hours and falls again liver and their metabolic situation to normal from 48 hours on (fig.l),while have been likened for certain aspects to glutammate level (fig. 2) undergoes neoplastic cells, and thus their charact- opposite variations at the same times erization is of particular interest. after surgery. Tfie change in bandwidth of 13C spectra after hepatectomy (fig. 1) suggests a decrease in the level of lipid peroxid- 72 ation, with a minimum content of radic- als between 24 and 36 hours after oper- 60 ation. 48 72h 36 36 h 24 1 12 control 6h k cont rol 150 100 50 ppm from TMS 180 170 160 ppm from TMS Fig.l - '^C spectra of regenerating Fig.2 - Carbonyl region of 13c spectra liver tissue of rats. of regenerating rat liver tissue. 266 Bulletin of Magnetic Resonance CORRELATION STUDY BETWEEN PROTON RELAXATION TIMES IN-VITRO AND HUMAN BRAIN TUMORS HISTOLOGY J.D. de CERTAINES*, L. BEKOIST*, F. DARCEL-MENAULT**, H. CHATEL**, A.M. BERNARD* * Laboratoire de RKN Medicale et ** Laboratoire de Heuropathologie - Faculte de Medecine - 35000 RENNES FRANCE. The various NMR imaging samples techniques (inversion-recovery, White matter samples : saturation-recovery, spin-echo) Centrum seiai-ovale 2 296 8 97 1 can generate images from i-lattice (Ti7 and spin-spin Internal capsule 2 254 3 89 1 , and spin-density, either Corpus collosum 2 282 3 95 5 .ndependently or in combination. Nuclear structures : The choice and interpretation of the images then depend on a sound Caudate Nucleus 567 47 105 6 knowledge of the variations in T^ Medulla 319 1 112 3 and To values in normal or Cortical samples : pathological tissues according to the hi s tology• Gray matter from isocortex 605 1 107 2 Proton relaxation times Ti and Cerebellar cortex 605 21 117 4 T2 were measured at 20 MHz, 22°C, on a Bruker PC 20 spectrometer by In comparison with these values, 180° - T - 90° pulse sequence for each pathological human sample had Ti and by the a high T-] and T2. Visceral tumour Meiboom-Gill-Carr-Purcell method and meningioma metastases have a Ti for T2« Measurements were taken of between 500 and 800 ms and a T2 less than 2 hours post-excision. of between 100 and 150 ms. For The samples were preserved in gliomas and medulloblastomas, Ti sealed tubes at 4 C. ranged between 500 and 1200 ms and Our series is made up of 137 T between 100 and 300 ms. For 2 VD1 specimens taken from 98 patients normal values, the uppex r T2 limit with intracranial tumours. 1 00 ms If a threshold is set at - 36 meningiomas 800 ms for T-| and at 150 ms for T2 - 45 gli omas : 1 1 grade II 90 % of the metastases and 23 grade III meningiomas are below it and 50 % 1 1 grad e IV of the gliomas are above it. No - 5 medulloblastomas statistical difference appeared - 19 metastases. between malignant and benign The normal brain was studied in gliomas. T-j and To correlated well a dog in the same experimental Numerous histological factors condi tions• can explain these variations : An important diffence was found oedema, microkystic formations, to exist between grey substance necrosis, etc. If for example, (Ti=581 ± 45 ms)(T2=107 ± 7 is) x and the importance of fibrosis is white substance (T-]=274± 19ms) estimated in various fibroblast (T2=98± 10 msj for which the meningiomas by colouring with average T-] value can be divided Masson trichrome, T^ variations into a short component (Tis = 4± (of up to 100 ms) for the same 14 ms) and a long component v T 2 = tumor can be explained. 445 ± 56 ms). This difference This work shows that if between grey and white substance propers in understanding Ti and explains the variations which can T 2 variations in biological be observed according to the tissues is to be made, then . anatomical localizations. E.g in-vitro experiments, which allow close comparisons between NMR and histology, are a necessary step. Esf 6 rfinc 6 * BEKOIST L.'ALLAIN J, LINEE P, HENNON MC, BERNARD AM VAN DEN DRIESSCHE J LE POLLES JB, de CERTAINES J : Interet de la RMN du proton dans 1'etude pharmacologique de 1'oedeme cerebral, (sous presse) Vol. 5. No. 267 H-SPIN-LATTICE RELAXATION TIME MEASUREMENTS IN TISSUES: EFFECT OF SURGICAL OPERATION ON T, VALUE OF RAT LIVER SAMPLES A. Di Nola (+)., E. Brosio, P. Fantazzini, L. Lendinara and F. Novello Istituto di Chimica-Fisica, Universita di Roma - P.le A. Moro, 5 00185 Italy The water proton spin-lattice relaxa 19 ms, T = 276± 7 ms ). No signi- 1,normal ° tion times (T ) of rat liver samples ta_ ken at different times (up to 48 hours) ficant difference of T between hepatec- after partial hepatectomy are reported. tomized and sham operated rats is obser- In this system the proton T is due to a ved. homogeneous cell population because he - Since the surgical operation does not patocytes constitute 90-95% of the total stimulate the DNA synthesis is sham ope- hepatic volume. The T values obtained rated rats (1), the increase of T cannot are compared with those of liver samples be correlated to the cell cycle as obser- from sham operated rats and of liver sam ved in sinchronized Hela cells (2). As it pies from rats that had not undergone is well established that stress and sham any surgical treatment (normal samples). operation affect ATP metabolism, nucleoti The results obtained are reported in Ta- de pools, RNA and protein synthesis and ble 1. cause also a long lasting increase in Table 1 a -glicoprotein, the observed variation of T values may reflect some of these me Average T values and standard error of tabolic changes. regenerating, T (R), and sham operated, The results emphasize the importance T (S), rat liver samples at different ti^ of the choice of a suitable control and mes after surgical operation; D= T (R)~ of the standardization in sample prepara- T (S) differences; significance level, tion for T measurements in biological as established by _t test, is reported if systems. _.O5. REFERENCES time T (R) n.of T (S) n.of D P (hour) (ms) rats (ms) rats (ms) 1 N.L.R. Bucher and R.A. Malt, "Regenera- tion of Liver and Kidney" Little ;Brown 5 313± 6 5 291± 7 4 22± 9 -.025 Boston (1971) p. 17-54. 10 322± 6 6 300i 3 4 22+ 8 -.025 2 P.T. Beall, C.F. Hazlewood and P.N, Rao, 20-24 354± 9 8 325± 7 6 29±12 _.O25 Science 192, 904-907 (1976). 26-30 357+.19 5 343+.11 5 14+.22 32-36 353±15 6 340+11 6 13+18 48 327±12 3 296+ 3 3 31±12 _.05 The results show that the T values of both hepatectomized and sham operated rats depend on the time after the surgi- cal operation-T increases with a maxi- mum value at 20-36 hours (T, = 357 +• l,max 268 Bulletin of Magnetic Resonance SIGNIFICANCE OF XH-IJMR RELAXATION TIME MEASURMENT IN BRAIN EDEMA., CEREBRAL INFARCTION AND BRAIN TUMORS YoHorikawa, S.Naruse, CoTanaka, KoHirakawa, HoNIshikawa, K.Yoshizaki Kyoto Prefectural University of Medicine, Department of Neurosurgery and Physiology, Kamigyo-Ku, Kyoto 602, Japan The state of water molecule in normal normal brain by measurement of relax- brain, edematous brain and brain tumors ation timeso However, these changes of were studied with measurement of 1H-NMR relaxation times did not always cor- relaxation times„ Edemas were induced respond to the histological types of experimentally by cold injury and TET brain tumorso And some of the tumors intoxication in Wistar rats, and as well could not be differenciated from brain as by unilateral carotid artery ligation edema only from the value of proton re- in Mongolian Gerbils. Human brain tumors laxation times „ were obtained at surgery. Longitudinal These results will offer the funda- (Tl) and transverse(T2) relaxation times mental interpretation of NMR-CT, which were measured with inversion recovery is recently available to clinical use. method and Meiboom-Gill pulse sequence Reference, (l) S»Naruse, Y.Horikawa, respectively at 100 MHz using JEOL PFT- C.Tanaka, KoHirakawa, H.Nishikawa, K. 100 NMR spectrometero Water contents of Yoshizaki: J Neurosurg 56:7^7-752, 1982 the samples were measured by dry and wet method after the NMR measurement,, In the normal brain of rats, II values were • Infarction (sec-') 1000-1100 msec and T2 values were 75-77 OCold Injury (Gray Matttr) 15 msec. In the edematous brain, Tl prolong- XCold Injury (White Matter) ed and T2 separated into two components, A TET Intoxication (White Matter) slow and fast oneo These changes of re- laxation times depended on the degree of edema and returned to normal values when edemas were.subsided in each type of A\3 brain edema. By the quantitative analysis of relaxation time and water content using relaxation rates(R1,R2), which are reciprocal number of relaxation times A\5 (Fig.1,2), we found that prolongation of Tl corresponds to the increase of water content in the edematous tissueso Also we found that T2 varies according to the days types of brain edema, and this variety depend on the content of large molecules such as proteins in the increased edema fluid. T2 reflects well the pathophysio- 77 78 79 80 81 82 83 <*) logical state of water molecule in the Water Content tissue(l). We used human brain tumors such as Figure legend: glioblastoma, astrocytoma, meningioma, (l) Relationship between longitudinal met astatic brain tumor, ependymoma, acous- relaxation rate(RlX and water content tic neurinoma, pituitary adenoma and so during the course of edema formation in on for the measurement of proton relax- cold injury and TET intoxication and ation times and compared with these of also during early stage in cerebral in- normal rat brain and of edematous brain farction. (Figo3)» Prolongation of Tl and separa- tion of T2 into two components were ob- served in many cases of tumors. Therefore, we can differenciate brain tumors from Vol. 5. No. 3A 269 NUCLEAR MAGNETIC RELAXATION IN TISSUE: MECHANISM AND CONTRAST EFFECT R. Kimmich, F. Winter Universitat Ulm, Sektion Kernresonanzspektroskopie 7900 Ulm, Fed. Rep. Germany In previous papers (1-3) we have shown that nuclear spin lattice : MUSCLE TISSUE relaxation of cells and tissue is governed by N H groups. This sta- .^'"'" native 0°C tement holds as long as the reso- nance frequency is near or below t i about 10 Hz and as long as pro- teins provide the major macromole- y cular constituents of the systems. Experimental evidence for these y relaxation sinks was found with ,.-• the observation of quadrupole dips /' '"* lyophilized indicating rapid magnetization -•'•" 0 °C transfer to the N nuclei. This i i 1 isotope has almost 100 % natural abundance and is strongly coupled y to the lattice via quadrupolar in- y teraction with electric field gra- - - dients. Provided the correlation y times of the ^4N^H interaction are long enough, the longitudinal pro- ? ' lyophilized ton relaxation times will be shor- r ^•'' ' -AO'C tened at the frequencies where the 1 1 1 resonance of the two nuclei coin- cide. The detection of quadrupole dips (1-3) thus proves the domi- lyophilized nance of this mechanism. This .-»-•' -100°C means that in the low-frequency I I .,1 regime protein backbone fluctua- 10 10= 10 10' B/Hz tions are more effective than si- fig. 1: Proton T^-dispersion of muscle de group motions. tissue. The dips predominantly have been The conclusion is that the con- found in dry systems, where the trast effect observed in NMR tomo- correlation times are long enough graphy on the basis of spin lattice (fig. 1). Nevertheless this mecha- relaxation is due (i) to the pro- nism is expected to be relevant tein concentration and (ii) to the also in systems with shorter cor- dynamic state of the protein back- relation times like protein solu- bones, which should be affected by tions and native cell systems: any major structural alteration. There is no reason why then back- bone fluctuations or tumbling of 1 . R . , Kimmich, F . Winter, the whole macromolecules should be Bull.. Magn. Resonance, 2, 3349 (198O) less important at frequencies be- 2. F.. Winter, R. Kimmich, low about 1O Hz. Merely the cor- Mol . Phys .,45, 3 3 (1982) relation times can become so short, 3 . F . Winter, R. Kimmich, that the dip conditions (2) partly Biochim. Biophys . Acta, will be violated. Accurate measu- 719, 292 (1982) rements of muscle tissue indicated 4. F . Winter, R. Kimmich, weak quadrupole dips (fig. 1) even Biophys. Struct. Mechanism, in the native state (4) . 7, 3:33 (1981) 270 Bulletin of Magnetic Resonance PROTON NMR VARIATIONS OP T1 AND T2 IN HUMAN THYROID GLANDS DEPENDING ON THEIR HISTOLOGY. JJ LE JEUNE*, D BEURTON**, AM BERNARD*, L BENOIST*, G LANCIEN**, J de CERTAINES*. * Laboratoire de RMN Medicale, Faculte de Medecine, 35000 RENNES FRANCE. ** Laboratoire d'Anatomie Pathologique - Pontchaillou, 35000 RENNES FRANCE Proton NMR has not yet been The whole sample was used for widely used to study the thyroid histomorphometric quantification gland. SHARA (1) and SINADINOVIC of the different structures. The (2) have suggested that relaxa- pourcentage of colloid, vesicular tion times can be important in cells and fibrosis in the sample diagnosing thyroid disease. Pre- was thus defined. vious results (de CERTAINES -3) Two histological characteris- have compared 99mTc scintigraphic tics were retained for result data with proton T-) and T2 in analysis. Tissue activity was thyroid disease. The present quantified by the vesicular cell- study was undertaken to investi- colloid ratio and tissue modifi- gate these fluctuations according cation by the fibrosis content. to the histological structure. For each group of patients, Forty patients were studied : the results obtained confirmed 31 had an adenomatous goiter, 6 previous experiments. Ti and T2 toxic adenoma, 2 cancer of the proton relaxation times as func- thyroid and 1 Grave's disease. tions of fibrosis content were The relaxation times T-| and T2 compared to earlier results con- of 2 tissue samples were measured cerning fibroblast meningiomas (4) less than 1 hour post-surgery (where the fibrosis content had with a Bruker PC 20 spectromete been coloured with Masson at 20 MHz and 3°C. One sample h trichrome and then measured). T-) been taken from the nodular or r and T2 variations can be more neoplastic region and the otherad accurately interpreted when from supposedly normal tissue, histological factors are taken was measured by pulse 180° - x - into account in result analysis. 90° and T2 by the Meiboom-Gill- Carr-Purcell method. References : 1 - SCHARA M, SENTJURC M, AUERSPERG M, GOLOUH R. Br. J. Cancer, 29, 483-486, 1974- 2 - SINADINOVIC J, RATKOVIC S, KRAINCANIC M, JOVANOVIC M. Endokrinologie, 69, 1, 55-66, 1977 3 - de CERTAINES J, HERRY JY, BENOIST L, LANCIEN G, BERNARD AM, LE CLECH G. Journal of Nuclear Medicine 23 (1), 48-51, 1982. 4 - De CERTAINES J, BENOIST L, DARCEL-MENAULT F, CHATEL M, BERNARD AM: Correlation study between proton relaxation times in-vitro and human brain tumors histology. Vol. 5, No. 3A 271 IN VIVO 31P NMR STUDIES ON EXPERIMENTAL TUMORS USING TOPICAL MAGNETIC RESONANCE (TMR) Naruse S*, Horikawa Y, Tanaka C, Higuchi T, Ueda S, Hirakawa K, Nishikawa H and Watari H Kyoto Prefectural University of Medicine, Department of Neurosurgery Kamigyo-Ku, Kyoto 602, Japan Energy metabolism in tumor tissue has each othero And spectra of neuroblas- been studied using biochemical methods. toma were similar to these of glioma But energy metabolism in vivo can not be except the much higher peak of sugar measured by this method* Recent advance phosphate in neuroblastoma„ in technology made it possible to mea- Several chemotherapeutic agents were sure the 31P-NMR spectrum in the living administrated to the animals intra- animals„ With use of this latter meth- vesnously and their effects on the 31P od, we studied in vivo energy metabolism NMR spectrum of the tumor were monitor- of brain tumors and examine the effects ed o Whether the 31P NMR spectra changed of chemotherapy on the tumors„ or not depended on the dose and the kind Experimental tumors were transplanted of the administrated drugs„ Changes of in CDF rats and humsters with injecting 3 *P NMR spectrum after the chemotherapy cultured cells of gloma, glioblastoma is shown typically in a case of neuro- and neuroblastoma subcutaneously in the blastoma (Figo2). Peaks of ATP de-, lumbar region. In vivo measurements of creased and a peak of Pi increased eight 31P NMR spectra were made on a TMR-32 hours after injecting vincristine at a spectrometer (Oxford Research Systems, dose of 2mg/kg body weight„ There were England). Typical spectrum of the rat no changes in the spectrum of the other glioma is shown in Fig.l, comparing with tissues such as muscle at the same peri- that of the normal rat brain. There are od in the same animal ,> And no histolcg- several sharp peaks in the spectrum,, ical changes were found in this period- They are; I, 3-ATP; II, a-ATP and a-ADP This indicated that the chemotherapeubic including NAD+/NADH; III, y-ATP and (3- agent may have the action to damage the ADP; IV, phosphocreatine (PCr); V, phos- energy metabolism in tumor cells di- phodiesters or 2,3 DPG; VI, inorganic rectly o phosphate (Pi); VII, sugar phosphate» Measurement of 31P NMR spectra in A peak of PCr could be scarcely detected vivo using TMR is indispensable not only in the glioma„ Peaks of ATP and sugar to investigate the energy metabolism of phosphate are relatively higher in the tumor cells but also to evaluate the glioma than in the normal brain„ effects of chemotherapy on the tumors Spectra of the glioma in rats and of the both experimentally and clinically in glioblastoma in humsters are resembles the medical field. Fig . NORMAL RAT BRAIN Fig .2 12h posttreatment l/V"M -20 -10 0 10 20 30 -20 -10 0 10 20 30 272 Bulletin of Magnetic Resonance PROTON NMR SPECTRA 0J<' BKAIN TUMORS CTanaka*, S.Naruse, YoHorikawa, KoHirakawa, KoYoshizaki, Y.Nishikawa Kyoto Prefectural University of Medicine, Department of Neurosurgery Kamigyo-Ku, Kyoto 602, Japan Nuclear magnetic resonance (NMR) showed similar pattern in the spectrum becomes one of the topics of the day in to rat brain tissue. On the other hand, the medical field since NMR-CT has began human brain tumors showed different to be applied to clinical use. But in the pattern from normal rat brain. Typical NMR spectrum analysis of biological tis- spectrum of brain tumor is shown in Fig. 1 sue, phosphorous nuclei has been used bo H-EMR spectra of the tumors had only frequently for the study of energy meta- one or two signals at the position of bolisnio On the other hand, proton NMR signals II, III, and IV situated in the spectrum studies are few in spite of normal rats,, Signal VI was significant- existing large amount of proton nuclei ly diminished in the brain tumors, and in biological tissue. The reason is that this was well recognized comparing sig- water gives enomous peak in the spectrum nal VI in Figoa with in Fig.b. There and other peaks of proton are swamped in were also some differences in the spec- this large water signal« However we could tra among the various histological types succeeded to obtain proton nuclear mag- of brain tumors, such as glioblastoma, netic resonance (XH-NMR) spectra of the astrocytoma, ependymoma, meningioma, normal rat brain and human brain tumors pituitary adenoma and metastatic brain in the solid state by selective water tumors„ These differences in 2H-NMR saturation method using homogated decou- spectra seemed to depend on their own pling technique at 100 MHz(l). aH NMR chemical composition and metabolites. spectra of normal solid rat brains were For the non-destructive analysis of composed of a broad signal and eight tumor, 1H-NMR spectra will be an useful sharp signals (Fig0a)0 Signal VII, sit - method for the investigation of brain ated at 1»3 ppm from external reference tumor and other tumors„ (TMS), is assumed to be methylene radi- Reference, (l) KoYoshizaki, Y.Seo, cal of the lactate» Other sharp signals H.Nishikawa: Biophys Acta 678:283-291, were not assigned exactly at the pres- 1981 ent time, but it was considered that these other signals would refered to small molecules such as amino acids which was contributing the brain metabolism,, Human brain tissue obtained by surgery a) Rat brain VII III Glioblastoma 2 0 (ppm) Ho Vol. 5, No. 3A 273 IN VIVO 31P--NMR STUDIES ON DYNAMIC CHANGES OF ENERGY METABOLITES IN EAT BRAIN DURING ANOXIA. Satoshi YOKONO*, • Kenji OGLI, Atsuko YOKONO, Shoji NARUSE and Hiroshi WATARI Kyoto Prefectural University of Medicine, Dept.of Anesthesiology Kamigyo-Ku, Kyoto 602, Japan The 31P NMR analysis has recently be- mixed gases of 95% 02 and 5% C02, the en applied to biological tissues and or- energy metabolites levels and intracell- gans to detect energy metabolites such ular pH were restored to those of control as ATP, phosphocreatine, sugar phosphate in 4 rats of Group I. On the other hand, and inorganic phosphate without interve- 31P NMR spectra of 5 rats of Group I and ning laborious extraction or homogeniza- all of Group II showed irreversible chan- tion of the tissues and organs. However ges of energy metabolites levels and sev- ordinary 31P NMR measurements require ere intracellular acidosis. When oxigen complicated techniques. Furthermore, supply was withheld, the store of ATP de- an organ is obsereved as a homogeneous creased immediately which might be attri- system by ordinary NMR(l). TMR(topical buted to the continued hydrolysis cataly- magnetic resonance) is one of magnetic sed by cellular ATPase. The concomitant focusing where static nonlinear magnetic decrease of Per indicates the reaction, field gradients are combined to profile catalysed by creatine phosphokinase, pro- and restrict the effective homogeneous vides ATP at the expense of the Per store volume in applied fields(2). This has (4). facilitated the acquisition of 31P NMR 31P NMR spectra from TMR spectrometer spectra from a selected place within have enabled us to observe the sequential intact living animals(3). changes of energy metabolites in living This time, we applied the TMR to in- animals. vestigate the sequential metabolic cha- References. (1). D.G.Gadian, G.K.Radda nges in rat brain throughout the course , R.E.Richards and P.J.Seeley. Biochemi- of anoxia and resuscitation.. cal application of magnetic resonance. Anoxic anoxia was induced by inspi- Academic Press, New York, 1979, pp.463- ration of mixed gases of 95% of nitrous 533. (2). K.Tanaka, Y.Yamada, T.Shimizu, oxide(N20) and 5% of carbon dioxide(C02 F.Sano and Z.Abe. Biotelemetry,!:337-350 ) through tracheostomy under artificial ,1974. (3). R.E.Gordon, P.E.Hanley, D. ventilation. Fourteen Wistar rats(200g) Shaw, D.G.Gadian, G.K.Radda, P.Styles, P. were divided into two groups. Group I J.Bore and L.Chan. Nature,287:736-738, (9 rats) was administered mixed gases 1980. (4). B.J.Siesjo. Brain Energy Meta- for 4 to 6 minutes and Group 11(5 rats) bolism. John Wiley & Sons, Chichester, for 8 minutes. The 31P NMR spectra of 1978. rat brain showed several peaks in the spectra. They are B-ATP, a-ATP, y-ATP, phosphocreatine(Per), phosphodiesters, inorganic phosphate(Pi) and sugar phos- phates from the high to low resonant frequencies. In both groups, administration of mixed gases of 95% N20 and 5% C02 pro- duced a quick reduction in the levels of ATP and Per, and a concomitant incre- ase in the level of Pi within 2 minutes. Intracellular pH, calculated from the chemical shift of Pi, shoved acidosis. Immediately £fter r^u-cit^f >.on vitV 27* Bulletin of Magnetic Resonance Author Index Name See Page Name See Page Aberg.M. Glaser.J. 231 Damoder,R. Eaton,G.R. 176 Agarwala.B.V. 224 Darcel-Menault,F. Certaines,J.D.de 267 Aguanno.B.D1 Conti,L.G. 200 Davi s,J.L. Mims.W.B. 168 Alston,K.D. Manoharan.P.T. 255 Debuyst.R. 229 Andrew,E. 104 Declercq,J.-P. Debuyst.R. 229 Armstrong,R.L. 120 Dehmelt,H. 107 Arroyo, CM. Kispert.L.D. 237 Dejehet.F. Debuyst.R. 229 Arumugam.S. 226 Demco,D.E. Ursu,I. 218 Bahadur,H. 193 Descouts.P. Lenk.R. 204 Baiazy.M. 227 Devreux,F. Nechtschein.M. 146 Barak,J. Raizman,A. 210 Dinh.S.Tran Neumann,J.W. 257 Barak,J. Suss,J.T. 215 Doane,J.W. Chidichimo.G. " 137 Barkhuiysen.H. 194 Doane,J.W. Vaz.N.A.P. 219 Barna.E. Chi para.M.1. 199 Duddeck.H. 230 Bartels.D.M. 228 Duijvestijn.M.J. Smidt,J. 114 Beer.R.de Barkhuiysen.H • 194 Dyck.R.Van Dehmelt.H. 107 Bendall.M.R. 191 Eaton,G.R. 176 Bendel,P. James,T.L. 165 Eaton,S.S. Eaton,G.R. 176 Benga.Gh. 265 Ekiel,1. 248 Benoist.L. Certai nes,J.D.de 267 Eliezer.D. Rai zman,A. 210 Benoi st.L. Lejeune,J.J. 271 Fantazzi ni,P. Nola.A.Di 268 Bernard,A.M. Certai nes,J.D.de 267 Fedders.P.A. Norberg.R.E. 129 Bernard,A.M. Lejeune,J.J. 271 Ferr i,D. Glaser.J. 231 Berti ni,1. Luchi nat,C. 242 F i eldi ng.L. Eaton,G.R. 176 Beuran,F. Chipara.M.1. 199 Fitori,P. Ursu,1. 218 Beurton.D. Lejeune,J.J. 271 Franzi,R. Geoffroy.M. 201 Bhat.S.V. Arumugam.S. 226 Fronci sz.W. Hyde.J.S. 180 Boer,E.de 195 Fuj imoto,J.M. Brown,C.E. 184 Boer,E.de 196 Gabr ielse.G. Dehmelt,H. 107 Boer,E.de 197 Genoud.F. Nechtschein.M. 146 Bogdan.M. Ursu.l. 218 Geoffroy.M. 201 Boicel1i,C.A. 266 Geoffroy.M. Ki spert,L.D. 237 Borle.F. Seelig,J. 150 Georgescu.L. Chi para.M.1. 199 Boucher,J.P. Nechtschein.M. 146 Georgescu.R. Chi para.M.1. 199 Bowman,M.K. 188 Ger i g,J.T. 157 Boyce,J.B. Norberg.R.E. 129 G iuliani.A.M. Boicel1i,C.A. 266 Bramley.R. Strach.S.J. 186 Glaser.J. 231 Brodbeck.C.M. 198 Goldfield.E.M. Lai,K. 253 Brosio.E. Nola.A.Di 268 Golding.R.M. 126 Brown,C.E. 184 Goldman,M. 110 Burger,V.T. Brown,C.E. 184 Golemme,A. Chidichimo.G. 137 Bydder.G.M. 171 Gorenstein,0.G. 161 Bystrov.V.F. 152 Gorenstei n.D.G. Kallick.D. 251 Cai ri,M. Gerig.J.T. 157 Gorenstein.D.G. Lai.K. 253 Carr i ngton,A. 124 Gorenstein.D.G. Shah.D.O. 260 Casy,A.F. Ogungbamila,F.0. 258 Grenthe,1. Glaser.J. 231 Certaines,J.D.de 267 Greppi n,H. Lenk.R. 204 Certaines,J.D.de Lejeune,J.J. 271 Gribnau.M.C.M. Boer,E.de 195 Chatel.M. Certaines,J.D.de 267 Groombr idge.C J. Harris.R.K. 189 Chidichimo.G. 137 Groot.P.de Witters,J. 187 Chipara.M.1. 199 Guarner i,M. Marco,A.De 247 Conti,L.G. 200 Gunther.H. 232 Crooks,L.E. 173 Guntherodt,H.-J. Luders.K. 205 Vol. 5, No. l/h 275 Name See Page Name See Page Haas,L.J.de Wenckebach.W.Th. 220 Korb.J.P. 185 Hammond,S.J. Ger ig,J.T. 157 Kostka.A. Bowman,M.K. 188 Hara.H. Hyono,A. 250 Kowalewsk i,V.J. 143 Harris,R.K. 189 Kripal.R. 239 Herlach,F. Witters,J. 187 Kunwar,A.C. Khetrapal,C.L. 234 Higuchi,T. Hirakawa.K. 192 Kunwar,A.C. Khetrapal,C.L. 235 Higuchi,T. Naruse,S. 272 Kuppusamy.P. Manoharan,P.T. 207 Hirai,A. Hpr i i,F. 190 Kuriyamo.S. Hyono,A. 250 Hirai,A. 233 Laatikainen.R. 240 H i rakawa,K. 192 Lai,C.-S. Hyde.J.S. 180 H irakawa.K. Hor ikawa.Y. 269 Lai.K. 253 Hirakawa,K. Naruse.S. 272 Lakshmi narayana.M.R. Khetrapal,C.L. 234 Hirakawa,K. Naruse.S. 273 Lanci en,G. Lejeune, J . J . 271 Holmes,R.P. Benga.Gh. 265 Lawler,R.G. Bartels.D.M. 228 Hori i.F. 190 Lefkowitz.S.M. 241 Hor i i,F. Hirai,A. 233 Lejeune,J.J. 271 Horikawa.Y. Hi rakawa,K. 192 Lemai re,C. Armstrong,R.L. 120 Hor i kawa,Y. 269 Lendi nara,L. Nola,A.Di 268 Hor ikawa,Y. Naruse.S. 272 Lenk.R. 204 Hor i kawa,Y. Naruse.S. 273 Leopold,D.J. Norberg.R.E. 129 Hutch i nson.C.R. Sherman,M.M. 261 Lotjonen.S. Hynni nen.P.H. 249 Huynh-D i nh,T. Neumann,J.W. 257 Lotjonen.S. 254 ; Hyde.J.S. 180 Luchi nat,C. 242 i Hynni nen.P.H. 2i+9 Luders,K. 205 Hynni nen.P.H. Lotjonen.S. 254 Lupei,V. 206 Hyono,A. 250 Lupei,A. Ursu,1 . 217 1golen,J. Neumann,J.W. 257 Lupei,V. Ursu.l. 217 1ngman,L.P. Punkki nen,M. 133 Manci ni,M. Luchinat.C. 242 1sbasescu,0. Chi para.M.1. 199 Mangr ich,A-S. Vugman.N.V. 246 1ton.L.E. Brodbeck.C.M. 198 Manoharan,P.T. 207 1ton.L.E. 202 Manoharan,P.T. 255 James,T.L. 165 Marco,A.De 247 Janssen.P. Witters,J. 187 Masui,M. Hyono,A. 250 Jaror i,G.K. Kenkare.U.W. 252 Matzkanin.G.A. 208 Jarrell.H.C. Ekiel,1. 248 McConnell.H.M. Korb,J.P. 185 Kalkeren.G.van Boer,E.de 196 Meerssche.M.Van Debuyst.R. 229 Kalkeren.G.van Boer.E.de 197 Mehta.A. Kenkare.U.W. 252 Kaliick.D. 251 Menegatti,E. Marco,A.De 247 Kawamor i,A. 203 Mims.W.B. 168 Keepers,J.W. James,T.L. 165 Misra.B.N. Kripal,R. 239 1 Keijzers.C.P. Boer,E.de 196 Miyachi, Oh-hama,T. 259 ' Keijzers.C.P. Boer.E.de 197 More.K.M. Eaton,G.R. 176 Kenkare.U.W. 252 Murali kr i shna,C. Subramani an.S, 213 Kennedy,R.A. Carrington,A. 124 Muralikrishna.C. Subramanian,S. 214 i Kesavan.T.R. Murty.V.S. 256 Murty.V.S. 256 Kesteren.H.W.van Wenckebach.W.Th. 222 Murugesan.R. Boer.E.de 195 Khetrapal,C.L. 140 Naruse.S. Hirakawa.K. 192 Khetrapal,C.L. Agarwala.B.V. 224 Naruse.S. Horikawa.Y. 269 Khetrapal,C.L. 234 Naruse.S. 272 Khetrapal,C.L. 235 Naruse.S. Tanaka.C. 273 Kimmich,R. 270 Naruse.S. Yokono,S. 274 Kispert,L.D. 237 Nechtschein.M. 146 Kitamaru.R. Hor i i,F. 190 Neumann,J.W. 257 Kitamaru,R. Hi rai,A. 233 Nicula.Al. 209 Ki tamaru.R. 238 Nieman.R.A. Gerig.J.T. . 157 ! Klinkenborg.J.C. Gerig.J.T. 157 Ni shikawa,H. Hirakawa,K. 192 Knights.J.C. Norberg.R.E. 129 Nishi kawa.H. Horikawa.Y. 269 276 Bulletin of Magnetic Resonance Name See Page Name See Page Ni shikawa.H. Naruse.S. 272 Sprott.G.D. Ekiel,1. 248 Nishikawa.Y. Naruse,S. 273 Srinivasan.R. Si nha,S. 212 Nistor.S.V. Ursu,1. 216 Srinivasan.R. Arumugam.S. 226 Nola.A.Di 268 Stoicescu.C. Lupei,V. 206 Norberg.R.E. 129 Strach.S.J. 186 Norr is,J.R. Bowman,M.K. 188 Subczynski,W.K. Hyde.J.S. 180 Novello,F. Nola.A.Di 268 Subramanian.S. 213 Ogli,K. Yokono.S. 274 Subramanian.S. 214 Ogungbamila,F.0. 258 Suryaprakash,N. Khetrapal,C.L. 235 0h-hama,T. 259 Suss,J.T. 215 Ohno.K. 243 Taboury,J. Neumann,J.W. 257 Ormondt.D.van Barkhui ysen.H. 194 Tanaka,C. Hi rakawa,K. 192 Packer,K.J. Harris.R.K. 189 Tanaka.C. Hor i kawa,Y. 269 Palmer,M.H. 244 Tanaka,C. Naruse.S. 272 Parshad.R. Bahadur,H. 193 Tanaka.C. 273 Pascual,R.O. Golding.R.M. 126 Taylor,J.E. James.T.L. 165 Pei sach,J. Mims.W.B. 168 Travers,J.P. Nechtschein.M. 146 Pop.V.1. Benga.Gh. 265 Trif,E. Nicula.Al. 209 Popescu.O. Benga,Gh. 265 Tr i funac,A.D. Bartels.D.M. 228 Poulis.N.J. Wenckebach.W.Th. 220 Tri funac.A.D. Lefkowitz.S.M. 241 Pouli s,N.J. Wenckebach.W.Th. 221 Ueda.S. Naruse.S. 272 Poulis.N.J. Wenckebach.W.Th. 222 Ursu,1. 136 Poulis,N.J. Wenckebach.W.Th. 223 Ursu,1 . Lupei,V. 206 Prabhananda,B.S. 2hS Ursu,1. 216 Punkki nen.M. 133 Ursu,1 . 217 Rai zman,A. 210 Ursu,1. 218 Rai zman,A. Suss,J.T. 215 Vaz.N.A.P. 219 Ramanathan.K.V. Agarwala.B.V. 224 Vel ter-Stefanescu.M. Ursu, 1 . 216 Ramsey,N. 112 Visintainer,J. 263 Rao,J .L. Kawamor i,A. 203 Vos.G.De Wi tters,J. 187 Rifkind.J.M. Manoharan.P.T. 255 Vugman.N.V. 246 Roer i g,S.C. Brown,C.E. 184 Watari,H. Hi rakawa,K. 192 Roth.G. Luders.K. 205 Watari,H. Naruse.S. 272 Samskog,P.-0. Kispert.L.D. 237 Watari,H. Yokono.S. 274 Sandhu.H.S. 211 Wenckebach.W.Th. 220 Schenk.G.J. Wenckebach.W.Th. 222 Wenckebach.W.Th. 221 Schloman.W.W.Jr. Vi s i ntai ner,J . 263 Wenckebach.W.Th. 222 Schmidt,J. Wenckebach.W.Th. 222 Wenckebach.W.Th. 223 Schmitt.P. Gunther,H. 232 Wesener,J.R. Gunther,H. 232 Schwi nberg,P. Dehmelt.H. 107 Wind.R.A. Smidt,J. 114 Seelig,J. 150 Winter,F. Kimmi ch,R. 270 Seto.H. Oh-hama,T. 259 Witters,J. 187 Shah.D.O. Kallick.D. 251 Wood,J.S. Boer,E.de 196 Shah.D.O. 260 Wood,J.S. Boer,E.de 197 Sherman,M.M. 261 Yarmush.D.M. Spr inger,C.S.Jr. 262 Simon.S. Nicula.Al. 209 Ylinen.E.E. Punkkinen.M. 133 S i nha,S. 212 Yokono.S. 274 Smidt,J. 114 Yokono,A. Yokono.S. 274 Smi th,J.A.S. Palmer,M.H. 244 Yoshizaki,K. Hor i kawa,Y. 269 Smith,1.C.P. Ekiel.i. 248 Yoshizaki,K. Naruse.S. 273 Softley.T.P. Carrington.A. 124 Young,1.R. Bydder.G.M. 171 Solomon,1 . 118 Zamir,0. Raizman,A. 210 Sousa,J.J.F.de Vugman.N.V. 246 Zetta.L. 264 Spi na,G. Luchinat.C. 242 Zon.C.M.B.van der Wenckebach.W.Th. 220 Spi rlet.M. Debuyst.R. 229 Zon.C.M.B.van der Wenckebach.W.Th. 221 Sprenkels,J.C.M. Wenckebach.W.Th. 223 Zonneveld.P. Wenckebach.W.Th. 221 Spri nger,C.S.Jr. 262 Vol. 5, No. 3/4 277