DOCSLIB.ORG

31P Nuclear Magnetic Relaxation Studies Ofphosphocreatine

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
31P Nuclear Magnetic Relaxation Studies Ofphosphocreatine Proc. Natl. Acad. Sci. USA Vol. 74, No. 10, pp. 4271-4275, October 1977 Biochemistry 31P nuclear magnetic relaxation studies of phosphocreatine in intact muscle: Determination of intracellular free magnesium (nuclear Overhauser effect/13C nuclear magnetic resonance) SHEILA M. COHEN*t AND C. TYLER BURTt *Department of Chemistry, University of Illinois at Chicago Circle, Chicago, Illinois 60680; and *Department of Biological Chemistry, University of Illinois at the Medical Center, Chicago, Illinois 60612 Communicated by Irving M. Klotz, July 25, 1977 ABSTRACT 31P nuclear magnetic relaxation rates for nipulations were performed in a cold room at 40 and NMR phosphocreatine in intact frog gastrocnemius were compared accumulations in a probe maintained at 40 were begun im- with those observed in model solutions at 40, a temperature at which muscle maintains its physiological state for at least 5 hr. mediately. Both nuclear Overhauser effect and spin-lattice relaxation rate PCr was from Sigma Chemical Co.; Mg(NO3)2 (ultrapure) (1/Tj) experiments indicate that interactions form was from Alfa Products. Metal-free solutions of PCr were the dominant relaxation path fordirle-dipoleP in intact muscle and model prepared by passing constituents through a column of Chelex. solutions, independent of phosphocreatine and Mg concentra- The pH was adjusted to 7.4 (pD = meter reading + 0.4) at room tions. Spin-spin relaxation rates (1/T2) measured by modified temperature with HCO (or DCl) prepared by passing Carr-Purcell-Melboom-Gill spin-echo experiments suggest the HCl (DCl) importance of scalar coupling modulated by chemical exchange gas through H20 (D20). Solutions were 0.1 M in KCI. Solutions with free Mg. From these results, we estimate the free intra- in deuterated solvent were lyophilized three to four times in cellular Mg in intact muscle as 4.4 mM and demonstrate that 99.8% D20. The final concentration of PCr in solution was 31p T2 experiments can be used as a tool for studying free Mg determined by total P analysis (9). Analyses for Mg and Mn in levels with minimum disturbance of the intact cell. stock and final solutions were by Trace Elements Inc. (Park Ridge, IL); these analyses showed Mn in final solutions to be 31P nuclear magnetic resonance (NMR) studies of intact cells <0.1 ,uM. All solutions were degassed either by nitrogen bub- to date have concentrated on high-resolution spectra of me- bling or several freeze-pump-thaw cycles. tabolites in intact muscle (1, 2), erythrocytes (3), yeast (4), and High-resolution NMR spectra were obtained at 36.43 MHz Escherichia coli and Ehrlich ascites tumor cells (5, 6). We report on a hybrid Bruker HFX-90 spectrometer with 2H stabilization here on the feasibility of measuring the relaxation parameters operating in the Fourier transform mode as described (10). of phosphocreatine (PCr) in intact frog muscle at 4°. The Spinning 10-mm samples were used; the field was locked either spin-lattice relaxation time (TI) and the spin-spin relaxation to a capillary of D20 (muscles and PCr/H20 solutions) or D20 time (T2) of PCr in intact muscle are compared with those solvent. Typical conditions included a 900 pulse of ca 20 lisec, observed in model solutions at 4°. Both relaxation rates are 32-128 scans of 4000 data points each, sweep width of 1 kHz, valuable as dynamic probes of the internal environment in exponential multiplication introducing 0.6-Hz line broadening, muscle because T2 can be sensitive to processes that do not affect and 'H irradiation. T, at all. These relaxation studies also enable us to assign a value T, measurements were made with the following pulse se- for the free intracellular Mg concentration in intact gastroc- quence: 900 pulse, spoil field homogeneity, wait delay time r, nemius via an intrinsically nonintrusive method. 90° pulse, sample free-induction decay, and then spoil field It is now clear that metal ions are of central importance in homogeneity. This sequence (11), which was repeated n times, many biological reactions and knowledge of free Mg levels has afforded a considerable saving of time over the inversion-re- particular significance. For example, Stephenson and Podolsky covery method in the T, regimen of 31P in PCr, thus making (7) showed that in skinned muscle fibers, Ca transport by intact it possible to carry out T, measurements on muscle during the sarcoplasmic reticulum is strongly influenced by Mg concen- interval in which there was no more than a 10% change in tration. The present nonperturbing technique for free Mg is of PCr. special interest; of the few alternate methods, the one of choice The Carr-Purcell-Meiboom-Gill (CPMG) (12) T2 mea- is probably a differential absorption procedure involving the surements were performed on a Bruker B-KR pulsed spec- microinjection of a Mg-binding dye to measure ionized Mg in trometer operating in conjunction with the same Nicolet data the volume surrounding a dialysis capillary (8). system and a 21.14 kG magnet used for high-resolution spectra. Two home-built modifications to the probe of this pulsed MATERIALS AND METHODS spectrometer were made so that satisfactory results could be Adult frogs, 5-12.5 cm in length, from Lake Champlain Frog obtained on biological samples in which phosphate metabolites Farm (Alberg, VT) were stored at 4°. Frogs appearing to be in are in the mM range-namely: (i) because field-frequency drift good condition were decerebrated and the rear legs were iso- is known to have a deleterious effect on the results of the CPMG lated. The gastrocnemius was dissected out and placed in a method, we installed an external deuterium lock system in the 10-mm NMR tube with standard frog Ringer's solution (113 pulse probe, which was capable of holding the 31p field-fre- mM NaCI/2.5 mM KCI/1.8 mM CaCl, pH 7.2). These ma- quency stability within 1-2 Hz over several hours, and (ii) in Abbreviations: NMR, nuclear magnetic resonance; PCr, phospho- The costs of publication of this article were defrayed in part by the creatine; T1, spin-lattice relaxation time; T2, spin-spin relaxation time; payment of page charges. This article must therefore be hereby marked CPMG, Carr-Purcell-Meiboom-Gill; NOE, nuclear Overhauser effect; "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate DD, dipole-dipole. this fact. t Present address: Bell Laboratories, Murray Hill, NJ 07974. 4271 Downloaded by guest on September 26, 2021 4272 Biochemistry: Cohen and Burt Proc. Natl. Acad. Sci. USA 74 (1977) _ 100 0 0 ~0 80 .0 0 0~ "F 60- 40 (a) (b) %4- 0 T= 277 K 20 A B A B 0 _ I w0 50 100I- 150 200 250 300 Minutes FIG. 1. Change in concentration (expressed as % of the original value) of whole-muscle phosphate metabolite as a function of time. There was less than a 20% change in PCr concentration over 5 hr at 40. This demonstrates the feasibility of long-term relaxation experiments at this temperature. The insets show two representative 31p spectra ofthe time course for change in PCr concentration (peak B) in whole muscle relative to a sealed reference.capillary of trimethyl phosphate (peak A). Experimental conditions were maintained constant throughout. (Inset a) The 0 min spectrum; the ratio of the integrated peak areas (B/A) is 0.73. (Inset b) A spectrum taken 290 min later in which this ratio is 0.64. order to use the significant gain in sensitivity offered by the of muscle were maintained within normal limits longer than large nuclear Overhauser effect (NOE) of 31P of PCr in muscle at room temperature (15). Typical 31P NMR spectra of the time (see below), we added proton irradiation capability to the 31P course for change in PCr concentration in whole muscle at 40 pulse probe. Whereas heteronuclear spin decoupling has a are shown in Fig. 1 inset. Long-term experiments requiring 4-5 complex effect on echo formation, the use of the NOE for signal hr were practical at this temperature; the data in Fig. 1 dem- enhancement does not contain this complication (13). Repro- onstrate that our muscle preparation maintained at least 80% ducible T2 values were obtained with the pulse spacings, 2r, of of this high-energy phosphate at the end of our longest exper- 2-20 msec used here. So that echo amplitudes could be mea- iments. sured relative to the proper steady state, the radio frequency Observed T1 values for several intact muscle samples and pulses were not turned off until the spin-echo decays had model solutions are listed in Table 1. Differences observed proceeded to about 6T2. Time averaging with a recycle time between stretched and unstretched muscle cannot be consid- of 6T, was used (14). Prior to averaging, signals were passed ered significant. However, it is significant that the average T, through a B-KR pulse-gated integrator whose output gave the of 4.8 sec for muscle and the average T1 of 4.9 sec for PCr in envelope of the echoes directly. CPMG measurements were simple aqueous solutions were the same within the stated error made on nonspinning samples in 10-mm tubes with the sample limits. This suggests that the system of 31P nuclear spins in PCr constrained within the radio frequency coil for greater H1 is relaxing by the same mechanisms in both cases. Comparison homogeneity. With muscle samples, this was accomplished by of T1 for PCr in H20 solution with T1 in D20 indicated that the choosing frogs of appropriate size so that a single gastrocnemius 'H-31P dipole-dipole (DD) interaction was the dominant re- almost filled the radio frequency coil space.
Load more

Recommended publications
  • 4 Nuclear Magnetic Resonance
    Chapter 4, page 1 4 Nuclear Magnetic Resonance Pieter Zeeman observed in 1896 the splitting of optical spectral lines in the field of an electromagnet. Since then, the splitting of energy levels proportional to an external magnetic field has been called the "Zeeman effect". The "Zeeman resonance effect" causes magnetic resonances which are classified under radio frequency spectroscopy (rf spectroscopy). In these resonances, the transitions between two branches of a single energy level split in an external magnetic field are measured in the megahertz and gigahertz range. In 1944, Jevgeni Konstantinovitch Savoiski discovered electron paramagnetic resonance. Shortly thereafter in 1945, nuclear magnetic resonance was demonstrated almost simultaneously in Boston by Edward Mills Purcell and in Stanford by Felix Bloch. Nuclear magnetic resonance was sometimes called nuclear induction or paramagnetic nuclear resonance. It is generally abbreviated to NMR. So as not to scare prospective patients in medicine, reference to the "nuclear" character of NMR is dropped and the magnetic resonance based imaging systems (scanner) found in hospitals are simply referred to as "magnetic resonance imaging" (MRI). 4.1 The Nuclear Resonance Effect Many atomic nuclei have spin, characterized by the nuclear spin quantum number I. The absolute value of the spin angular momentum is L =+h II(1). (4.01) The component in the direction of an applied field is Lz = Iz h ≡ m h. (4.02) The external field is usually defined along the z-direction. The magnetic quantum number is symbolized by Iz or m and can have 2I +1 values: Iz ≡ m = −I, −I+1, ..., I−1, I.
    [Show full text]
  • Relaxation 11/26/2020 | Page 2
    RUPRECHT-KARLS- UNIVERSITY HEIDELBERG Computer Assisted Clinical Medicine Prof. Dr. Lothar Schad Master‘s Program in Medical Physics 11/26/2020 | Page 1 Physics of Imaging Systems Basic Principles of Magnetic Resonance Imaging III Prof. Dr. Lothar Schad Chair in Computer Assisted Clinical Medicine Faculty of Medicine Mannheim University of Heidelberg Theodor-Kutzer-Ufer 1-3 D-68167 Mannheim, Germany [email protected] www.ma.uni-heidelberg.de/inst/cbtm/ckm/ RUPRECHT-KARLS- UNIVERSITY HEIDELBERG Computer Assisted Clinical Medicine Prof. Dr. Lothar Schad Relaxation 11/26/2020 | Page 2 Relaxation Seite 1 1 RUPRECHT-KARLS- UNIVERSITY HEIDELBERG Computer Assisted Clinical Medicine Prof. Dr. Lothar Schad Magnetization: M and M 11/26/2020 | Page 3 z xy longitudinal magnetization: Mz transversal magnetization: Mxy transversal magnetization: Mxy - phase synchronization after a 90°-pulse - the magnetic moments of the probe start to precede around B1 leading to a synchronization of spin packages → Mxy - after 90°-pulse Mxy = M0 RUPRECHT-KARLS- UNIVERSITY HEIDELBERG Computer Assisted Clinical Medicine Prof. Dr. Lothar Schad Movie: M and M 11/26/2020 | Page 4 z xy source: Schlegel and Mahr. “3D Conformal Radiation Therapy: A Multimedia Introduction to Methods and Techniques" 2007 Seite 2 2 RUPRECHT-KARLS- UNIVERSITY HEIDELBERG Computer Assisted Clinical Medicine Prof. Dr. Lothar Schad Longitudinal Relaxation Time: T1 11/26/2020 | Page 5 thermal equilibrium excited state after 90°-pulse: -N-1/2 = N+1/2 and Mz = 0, Mxy = M0 after RF switched off: - magnetization turns back to thermal equilibrium - Mz = M0, Mxy = 0 → T1 relaxation longitudinal relaxation time T1 spin-lattice-relaxation time T1 RUPRECHT-KARLS- UNIVERSITY HEIDELBERG Computer Assisted Clinical Medicine Prof.
    [Show full text]
  • Effect of Electronegative Elements on the NMR Chemical Shift in Some Simple R-X Organic Compounds
    IOSR Journal of Applied Physics (IOSR-JAP) e-ISSN: 2278-4861.Volume 6, Issue 4 Ver. III (Jul-Aug. 2014), PP 45-56 www.iosrjournals.org Effect of electronegative elements on the NMR chemical shift in some simple R-X organic compounds Muhammad A. AL-Jalali1, Yahia M. Mahzia2 1Physics Department, Faculty of Science, Taif University, Taif, AL-Haweiah, , P. O. Box 888, Zip code 21974, Kingdom of Saudi Arabia 2Physics Department, Faculty of Science, Damascus University, Damascus, Syrian Arab Republic. Abstract: Organic halides and other organic compounds that contain electronegative elements, have a strong chemical shift and a brilliant NMR spectrum will prevail. Relationship between 1H, 13C NMR chemical shift and Electronegativity in some simple R-X organic compounds (X=F, Cl, Br, I, O, H, ...R=CH3 or CH3-CH2-) give nonlinear equation, as well as a power series equation appears between nuclear magnetogyric ratio, magnetic shielding constant and chemical shift, which are not included in the theoretical expressions. More investigations required to remove the discrepancy between the theoretical and the experimental results. Keywords: Electronegativity, chemical shift, shielding constant, magnetogyric ratio. I. Introduction Nuclear magnetic resonance, or NMR is a physical phenomenon was observed in 1945[1,2], which occurs when the nuclei of certain atoms, firstly, subject to nuclear Zeeman effect[3,4,5]will Precession with the Larmor frequency [6, 7]. Secondly, exposed to an oscillating electromagnetic field (radio waves), then if the radio wave frequency exactly matches the precession frequency, the resonance phenomenon will happen and this is the so-called nuclear magnetic resonance. However, experimentally, it has been noticed [8, 9, 10] that a nucleus may have a different resonant frequency for a given applied magnetic field in different chemical compounds, this difference in resonant frequency is called the chemical shift or sometimes fine structure.
    [Show full text]
  • The Chemical Shift Chem 117 the Chemical Shift Key Questions (1) What Controls Proton Chemical Shifts? Eugene E
    E. Kwan Lecture 2: The Chemical Shift Chem 117 The Chemical Shift Key Questions (1) What controls proton chemical shifts? Eugene E. Kwan January 26, 2012. H H H H 0.86 ppm 5.28 2.88 Br Scope of Lecture 16.4 proton chemical problem shift trends diamagnetic vs. (2) What controls carbon chemical shifts? solving paramagnetic O O shielding O CH2 H C OH the chemical 3 H3C CH3 basic DEPT 49.2 49.2 40.5 69.2 and COSY shift H-bonding and solvent (3) What are COSY and DEPT? What useful information effects spin-orbit coupling, can they give about a structure? carbon chemical effect of unsaturation shift trends 123 Helpful References 10 0 1. Nuclear Magnetic Resonance Spectroscopy... Lambert, J.B.; 1 Mazzola, E.P. Prentice-Hall, 2004. (Chapter 3) 2 2. The ABCs of FT-NMR Roberts, J.D. University Science Books, 2000. (Chapter 10) 3 3. Spectrometric Identification of Organic Compounds (7th ed.) Silverstein, R.M.; Webster, F.X.; Kiemle, D.J. Wiley, 2005. (useful charts in the appendices of chapters 2-4) 10 4. Organic Structural Spectroscopy Lambert, J.B.; Shurvell, H.F.; Lightner, D.A.; Cooks, R.G. Prentice-Hall, 1998. I thank Professors William F. Reynolds (Toronto) and Gene Mazzola (Maryland/FDA) for providing some useful 5. Organic Structure Analysis Crews, P. Rodriguez, J.; Jaspars, material for this lecture. The section on chemical shifts M. Oxford University Press, 1998. is based on the discussion in Chapter 3 of reference 1. E. Kwan Lecture 2: The Chemical Shift Chem 117 Proton Chemical Shifts Clearly, the regions overlap: reference: Lambert and Mazzola, Chapter 3.
    [Show full text]
  • NMR Chemical Shifts of Common Laboratory Solvents As Trace Impurities
    7512 J. Org. Chem. 1997, 62, 7512-7515 NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities Hugo E. Gottlieb,* Vadim Kotlyar, and Abraham Nudelman* Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel Received June 27, 1997 In the course of the routine use of NMR as an aid for organic chemistry, a day-to-day problem is the identifica- tion of signals deriving from common contaminants (water, solvents, stabilizers, oils) in less-than-analyti- cally-pure samples. This data may be available in the literature, but the time involved in searching for it may be considerable. Another issue is the concentration dependence of chemical shifts (especially 1H); results obtained two or three decades ago usually refer to much Figure 1. Chemical shift of HDO as a function of tempera- more concentrated samples, and run at lower magnetic ture. fields, than today’s practice. 1 13 We therefore decided to collect H and C chemical dependent (vide infra). Also, any potential hydrogen- shifts of what are, in our experience, the most popular bond acceptor will tend to shift the water signal down- “extra peaks” in a variety of commonly used NMR field; this is particularly true for nonpolar solvents. In solvents, in the hope that this will be of assistance to contrast, in e.g. DMSO the water is already strongly the practicing chemist. hydrogen-bonded to the solvent, and solutes have only a negligible effect on its chemical shift. This is also true Experimental Section for D2O; the chemical shift of the residual HDO is very NMR spectra were taken in a Bruker DPX-300 instrument temperature-dependent (vide infra) but, maybe counter- (300.1 and 75.5 MHz for 1H and 13C, respectively).
    [Show full text]
  • Article Is Available Online Is One of the Most Comprehensive Ways to Envision Such at Doi:10.5194/Bg-13-2257-2016-Supplement
    Biogeosciences, 13, 2257–2277, 2016 www.biogeosciences.net/13/2257/2016/ doi:10.5194/bg-13-2257-2016 © Author(s) 2016. CC Attribution 3.0 License. Molecular characterization of dissolved organic matter from subtropical wetlands: a comparative study through the analysis of optical properties, NMR and FTICR/MS Norbert Hertkorn1, Mourad Harir1, Kaelin M. Cawley2, Philippe Schmitt-Kopplin1, and Rudolf Jaffé2 1Helmholtz Zentrum München, German Research Center for Environmental Health, Research Unit Analytical Biogeochemistry (BGC), Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany 2Southeast Environmental Research Center, and Department of Chemistry and Biochemistry, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA Correspondence to: Rudolf Jaffé (jaffer@fiu.edu) Received: 23 July 2015 – Published in Biogeosciences Discuss.: 25 August 2015 Revised: 22 December 2015 – Accepted: 7 February 2016 – Published: 19 April 2016 Abstract. Wetlands provide quintessential ecosystem ser- relative disparity was largest between the Everglades long- vices such as maintenance of water quality, water supply and short-hydroperiod samples, whereas Pantanal and Oka- and biodiversity, among others; however, wetlands are also vango samples were more alike among themselves. Other- among the most threatened ecosystems worldwide. Natural wise, molecular divergence was most obvious in the case dissolved organic matter (DOM) is an abundant and criti- of unsaturated protons (δH > 5 ppm). 2-D NMR spectroscopy cal component in wetland biogeochemistry. This study de- for a particular sample revealed a large richness of aliphatic scribes the first detailed, comparative, molecular characteri- and unsaturated substructures, likely derived from microbial zation of DOM in subtropical, pulsed, wetlands, namely the sources such as periphyton in the Everglades.
    [Show full text]
  • Proton Relaxation Times in Paramagnetic Solutions. Effects of Electron Spin Relaxation N
    Proton Relaxation Times in Paramagnetic Solutions. Effects of Electron Spin Relaxation N. Bloembergen and L. O. Morgan Citation: The Journal of Chemical Physics 34, 842 (1961); doi: 10.1063/1.1731684 View online: http://dx.doi.org/10.1063/1.1731684 View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/34/3?ver=pdfcov Published by the AIP Publishing This article is copyrighted as indicated in the abstract. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 75.183.112.71 On: Fri, 29 Nov 2013 20:41:28 842 L. C. SNYDER AND R. G. PARR cause the computed value of the property to depend of the test magnetic dipole. The presence of these on the origin taken for the vector potential. It also difficulties in the perturbation method should en­ is clear that caution must be exercised in applying sum courage the continued investigation of variation or 13 17 rules to estimate the excited state parts. With a single other methods - as the way to achieve quantitative average excited state energy the excited state part of computation of the magnetic properties of molecules. the magnetic susceptibility for a hydrogen atom can be ,estimated for any origin of the vector potential. How­ J3 M. J. Stephen, Proc. Roy. Soc. (London) A242, 264 (1957). ever, no single average excited state energy can give a J4 B. R. McGarvey, J. Chem. Phys. 27, 68 (1957). correct sum rule estimate of the excited state contribu­ J. J. A. Pople, Proc.
    [Show full text]
  • NMR Experiments for Structure Determination
    NMR Experiments for Structure Determination Dr Michael Thrippleton Introduction Nuclear Overhauser Effect (NOE) J-coupling •through space •through bond •J-spectroscopy •1D NOE •DQF COSY •2D NOESY •z-COSY •ROESY •HMBC The NOE Self-Relaxation pulse(s) relaxation Relaxation is the process by which magnetisation returns to equilibrium • longitudinal relaxation rate R1 • Transverse relaxation rate R2 The NOE Inversion recovery τ Magnetisation returns to +z axis during at rate R 1 •figures reproduced from Understanding NMR spectroscopy , by James Keeler The NOE Cross-relaxation The NOE Cross-relaxation Perturbation of spin I from equilibrium causes spin S to grow/shrink σ • cross-relaxation rate constant 12 • spins must be close in space The NOE Transient NOE •Target spin inverted and allowed to relax to equilibrium •Cross-relaxation generates NOE on neighbouring spin “mixing time” irradiated spectrum − Sirr Sref reference spectrum η = Sref difference spectrum NOE enhancement •figures reproduced from Understanding NMR spectroscopy , by James Keeler The NOE Transient NOE irradiated spin difference spectrum reference spectrum •figures reproduced from Stott et al., J. Magn. Reson. 125 , 302-324 The NOE NOESY •2D version of 1D transient NOE •takes longer, but contains more information •row from NOESY looks like 1D experiment •spectrum reproduced from Understanding NMR spectroscopy , by James Keeler The NOE Relaxation Mechanisms •Dipole-dipole coupling nearly averaged out by molecular tumbling •Remainder responsible for relaxation τ •Rate depends on timescale of motion c and distance between spins ( r-6 ) Small molecules, e.g. quinine τ •rapid motion / short c Large molecules, e.g. proteins τ tumbling •slow motion / long c The NOE How big, how fast? ω τ = 5 “zero crossing” 0 c 4 •slow / absent for v.
    [Show full text]
  • Measuring T1 and T2 Relaxation Times
    Relaxation Measurements Two Relaxation Mechanisms 90° pulse T1: Spin‐lattice or longitudinal relaxation is the average lifetime of the nuclei in the higher spin state T2: Spin‐spin or transverse relaxation corresponds to a de‐coherence of the transverse nuclear spin magnetization Spin‐Lattice Relaxation Time or T1 • Any factor which slows molecular motion (e.g. increasing solution viscosity, aggregation, or rigidifying the molecule) shortens the spin‐lattice relaxation time • A short T1 favors sensitivity but too short can result in line broadening and degradation of resolution since T2 cannot be longer than T1 • 3 principal magnetic interactions that contribute to T1 relaxation of spin ½ nuclei: o Dipole‐dipole interaction ‐ the nucleus experiences a fluctuating field due to the motions of neighboring dipoles, unpaired electrons, or other nuclei o Chemical shift anisotropy ‐ chemical shielding of the nucleus is a function of molecular orientation with respect to B0 field direction o Spin rotation interaction –small magnetic fields are induced at the nucleus as a molecule reorients; this field fluctuates because the motions are not uniform but proceed by a series of small jumps • Small amounts of paramagnetic substances speed up relaxation • Inversion recovery experiment measures T1 T1 Measurement: Inversion Recovery Parameters to note & Optimize • To change the value of the delay, d7, a variable delay list must be created. • In the acquisition parameters a VDLIST can be generated which contains values that typically cover a time range which extends past vdlist the expected T1 value. 0.05 0.5 Iz = I0(1‐2exp(‐d7/T1) 1.0 1.5 ln(I0‐Iz) = ln(2I0)‐d7/T1 2 Tnull = T1*ln2 4 6 8 Spin‐Spin Relaxation Time or T2 • T1 = T2 when molecular tumbling is fast compared with the Larmor frequency; this is the condition for small molecules.
    [Show full text]
  • Optical Detection of NMR J-Spectra at Zero Magnetic Field
    1 Optical detection of NMR J-spectra at zero magnetic field M. P. Ledbetter1, C. W. Crawford2, A. Pines2,3, D. E. Wemmer2, S. Knappe4, J. Kitching4, and D. Budker1,5 1Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 USA, 2Department of Chemistry, University of California, Berkeley, California 94720 USA, 3Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 USA, 4Time and Frequency Division, National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado, 80305 USA, 5Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720,USA Scalar couplings of the form JI1·I2 between nuclei impart valuable information about molecular structure to nuclear magnetic-resonance spectra. Here we demonstrate direct detection of J-spectra due to both heteronuclear and homonuclear J-coupling in a zero-field environment where the Zeeman interaction is completely absent. We show that characteristic functional groups exhibit distinct spectra with straightforward interpretation for chemical identification. Detection is performed with a microfabricated optical atomic magnetometer, providing high sensitivity to samples of microliter volumes. We obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz statistical uncertainty. We anticipate that the technique described here will provide a new modality for high-precision “J spectroscopy” using small samples on microchip devices for multiplexed screening, assaying, and sample identification in chemistry and biomedicine. 2 Nuclear magnetic resonance (NMR) endures as one of the most powerful analytical tools for detecting chemical species and elucidating molecular structure. The fingerprints for identification and structure analysis are chemical shifts and scalar couplings (1,2) of the form JI1 ·I2.
    [Show full text]
  • Spin-Lattice Relaxation Times Reading Assignment
    Spin-Lattice Relaxation Times Reading Assignment : T. D. W. Claridge, High Resolution NMR Techniques in Organic Chemistry , Chapter 2; E. Breitmaier, W. Voelter, Carbon 13 NMR Spectroscopy,3rd Ed., 3.3.2. Purpose Use the inversion recovery method to measure the T 1 relaxation times for the different chemical environments in a molecule. The T 1 values will be used to assess motion in different parts of the molecule. Introduction Spin-Lattice Relaxation When molecules absorb light they are transferred from lower energy states to higher energy states. This leaves the system out of equilibrium, and the system must undergo transitions from the upper states to lower states to get back to equilibrium. This process is illustrated in Figure 1. For nuclear magnetic resonance of protons, the energy level diagram has two energy levels, the lower state with protons "spin up", or aligned with the external field, and the higher state with protons "spin down", or aligned against the external field. Light in the radiofrequency region of the spectrum causes protons to "flip", or jump to higher energy levels. The process whereby the system returns to equilibrium involves spin flips to return to the lower energy state, and the excess energy is lost to the surroundings in the form of heat. The surroundings in magnetic resonance experiments is called the "lattice", therefore the name spin- lattice relaxation. The characteristic life-time of a spin in the upper state is called the spin-lattice relaxation time T 1. T 1 is the average length of time that a proton remains in the same energy level.
    [Show full text]
  • Normal Values of Magnetic Relaxation Parameters of Spine Components with the Synthetic MRI Sequence
    ORIGINAL RESEARCH SPINE Normal Values of Magnetic Relaxation Parameters of Spine Components with the Synthetic MRI Sequence X M. Drake-Pe´rez, X B.M.A. Delattre, X J. Boto, X A. Fitsiori, X K.-O. Lovblad, X S. Boudabbous, and X M.I. Vargas ABSTRACT BACKGROUND AND PURPOSE: SyMRI is a technique developed to perform quantitative MR imaging. Our aim was to analyze its potential use for measuring relaxation times of normal components of the spine and to compare them with values found in the literature using relaxometry and other techniques. MATERIALS AND METHODS: Thirty-two spine MR imaging studies (10 cervical, 5 dorsal, 17 lumbosacral) were included. A modified multiple-dynamic multiple-echo sequence was added and processed to obtain quantitative T1 (millisecond), T2 (millisecond), and proton density (percentage units [pu]) maps for each patient. An ROI was placed on representative areas for CSF, spinal cord, intervertebral discs, and vertebral bodies, to measure their relaxation. RESULTS: Relaxation time means are reported for CSF (T1 ϭ 4273.4 ms; T2 ϭ 1577.6 ms; proton density ϭ 107.5 pu), spinal cord (T1 ϭ 780.2 ms; T2 ϭ 101.6 ms; proton density ϭ 58.7 pu), normal disc (T1 ϭ 1164.9 ms; T2 ϭ 101.9 ms; proton density ϭ 78.9 pu), intermediately hydrated disc (T1 ϭ 723 ms; T2 ϭ 66.8 ms; proton density ϭ 60.8 pu), desiccated disc (T1 ϭ 554.4 ms; T2 ϭ 55.6 ms; proton density ϭ 47.6 ms), and vertebral body (T1 ϭ 515.3 ms; T2 ϭ 100.8 ms; proton density ϭ 91.1 pu).
    [Show full text]