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Depa1'tment of Physical Chemistry Isl'ael .. ANNUAL PROGRESS REPORT C00-3221-67 (For the period September 79 - July 80) Under Contract No. DOE/EV/03221 on THE NATURE OF OXYGEN CONTAINING RADICALS IN RADIATION CHEMISTRY AND PHOTOCHEMISTRY OF AQUEOUS SOLUTIONS Submitted by PROFESSOR GIDON CZAPSKI Depa1'tment of Physical Chemistry The Hebl'eW Univel'sity~ Jerusalem~ Isl'ael IJISTRIBUTIOJI OF THIS DOCUMENT IS UNUMITEJJ DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. ANNUAL PROGRESS REPORT C00-3221-67 (For the period September 79 - July 80) Und~r Contract No. DOE/EV/03221·· on THE NATURE OF OXYGEN CONTAINING RADICALS IN RADIATION CHEMISTRY AND PHOTOCHEMISTRY OF AQUEOUS SOLUTIONS Submitted by PROFESSOR GIDON CZAPSKI lh~s book was ~repared as an account of work sponsored by an agency of the United States Government :!:~; the ~~•ted Stat~ ~nment nor any agency thereof, nor any of their employees, makes an~ v. 8 P ess ot •mpl•ed. 01 assumes any legal llabiliry or responsibilily for thti accuracy completeness, or usefulness of any information apparatus Product 01 process d'sclosed ' represent~ thm its use v.ould not i~fringe private~ owned ri~ht" Ref~ence herein 10 :nv ~~~~ commerc•al Product, process, or serv•ce by trade name, trademark, manufacturer or otherwise does :,;=~~";itute or imply its endorsemenz. recommendation, or favc:ring by the UniU!C:I necessarily state or refl;~h= ~~~erUe;:i~-;~a7e~=nomepi~iloo": ..o: authors ehxpressedf herein do not . • .... y agency t ereo . .. Department of Physical Cherrristry The Hebrew University~ Jerusalem~ Israel bJs'rRlBUTION OF THIS DOCUMENT IS UNUMIT~ ----------------------------------~ ANNUAL PROGRESS REPORT (December 1979 - July 1980) ON THE NATURE OF OXYGEN CONTAINING RADICALS IN RADIATION CHEMISTRY AND .PHOTOCHEMISTRY OF AQUEOUS SOLUTIONS INSTITUTIONS This research will be carried out at the Department of Physical Chemistry and in the Linear Accelerator Department, The Hebrew University of Jerusalem, Israel. PRQJE.CT ABSIB8CI The proposed research is a continuation of the work donducted under this cnntract and is outlined. During this year, the main emphasis will be given to study further the p~operties of H0 and and OH', mainly in their role in biological 2 o; systems. We will continue to. study and elucidate how o; reacts in biological systems. The toxicity of o; is quite well established but the mechanism is still obscure. One way ·o; is toxic, .was shown .by us and :ot~e.rs, that OH' is .fonned from 3 2 o; through reduction of Fe +, and subsequently the reaction of Fe + with H2o2 (Fenton reaction). This mechanism is sometimes, unjustifiably, called the "Haber Weiss Reaction". 3 We will study if reduction of Fe + comple~es·by o; in biological systems does catalyze .the Haber Weiss reaction and if OH' is formed in .this mechanism. The role of oxygen, radiosensitizers in radiation damage of bacteriophages and cells will be further studied, .as well as,on E. Coli and En~ymes. Usin~ different mutants, such as ones with repair deficiencies, or others which are deficient in glutathione -these will help to elucidate the role of o; and 02 toxicity. ._ 2 - We. w~:11· trY.· to. ~~~cidate the formation and role of OH', o; and o2 in these sys­ tems as w~ll. ·a·~ ·the. l'E;!lative contribution of endogenous and exogenous damage, and the role of direct and indirect radiation damage to cells. As there is some doubt how and if SOD protects cel.ls from irradiation as litera- ture results show lots of conflict, we will try to clear this point, in studies with E. coli mutants, and adding SOD endogenously and exogenously. • . We also intend to study if SOD (super oxide dismutase) does react only with o; or also with biological peroxides (R0:2) and Hydropero,xides (RO;H). Further .studies of and 0 with various cytochromes .• and Hemoglobins is planned. o; 2 - 3 - RESEARCH PROPOSED O-RIGINALLY AND SUMMARY OF ACHIEVEMENTS DURING THE PREVIOUS YEARS The research project proposed originally was to investigate the physical and chemical properties of Ozonide and Hydro-peroxy radical mainly in aqueous solutions. We will summarize the results of the problems suggested and studied during the previous years by us . .., 1. OZONIDE ION We established the spectrum of this species as well as the decay and formation kinetics of the ozonide. The reaction mechanism and kinetics o; with other solutes were measured and shown to follow by the dissociation of 0~. · 2. HYDRO-PEROXY RADICAL We determined the properties of this species. It was shown that it exists as H0 2 and o; with pK - 4.85. The additional form of the radical H2o/ proposed, seems to be ruled out in solutions down to pH = 0. The decay scheme of the radical was well established, including the separate rate co~stants for the reactions H0 + H0 , H0 + and + The optical spectrum of H0 and were 2 2 2 o; o; o;. 2 o; determined. 3. COMPLEXES OF H0 WITH CATIONS 2 It was shown that H0 2 forms complexes with many cations yielding Ml-I0 2. These species are much more stable than the free radical, and they have typical ESR signa~s. It was found that these complexes undergo readily exchange reactions of the following type. 4. ESR DETECTION WITH IN SITU PHOTOLYSIS USING MODULATED LIGHT In this method radicals were generated in situ in an ESR cavity by photolysis. -5 The light source was modulated and square pulses with pulse length of 10 sec I were obtained with 'frequencies of 5Hz-4KHz. By this method, radicals reach .. /4 ·-4- concentrations at the end.of pulses which were as low as 1o"9M and decay till the next pulse. Using a wave from educator, one can average the ESR signal over many p~lses and good signal/noise is obtained although of the very low concen­ tration obtained by this method. In order to prevent depletion, the solutions being changed in the cavity by a slow flow system. This method was used to follow the decay kinetics of several complexes, such as Th-H0 2. The method has the advantage to follow reactions of Th-H0 2 at low concentrations, where 2nd order recombination is neglible while with usual techniques one can not prevent the 2nd order decay, as in these methods much higher concentrations of Th-H0 2.are formed. 5. ·EQUILIBRIA CONSTANfS OF MH0 2 COMPLEXES We further studied the equilib~ia of MH0 2 complexes (1) We determinated a few more values of such equilibrium constants with various methods. We also extended the study of the exchange reaction. M + M'H0 (2) 2 and varified and determined some new equilibria constants for this kind of exchange. 6. RATE AND MECHANISM OF COMPLEX FORMATION AND EXCHANGE REACTIONS We determined the rate of formation of MH0 through reaction (1) and the 2 4 6 exchange rates (reaction 2)·. for various cations, such as Th +, u +, etc. The result indicates that these rates are very fast, and the exchange mechanism (2) may go on either directly (2) or more probably through dissociation of MH0 2(1). 3 2 7. COMPLEXES OF Fe + AND Cu + WITH H0 2 . 2+ 3+ . We continued to establish the existence of complexes of Cu and Fe w1th Ho ' . Such complexes could be of interest, in view of the biological role of 2 3 2+ Fe + and Cu compounds in reactions with H0 2 in such systems. ; ./5 . 2+ Concerning the existence ·of CuH0 2 we got good kinetic evid~~ce, although this comlpex is short lived and therefore its concentration was too low to record its optical or ESR spectra. 8. OPTICAL SPECTRA OF MH0 2 While the existence of MH0 2 complexes were established and its ESR spectra recorded previously, their optical. spe.ctra were not known. Using the P\llse radiolysis we were able to observe the optical spectra of ThHo;: UHO~+ and study these species by absorption spectroscopy. 9. The radical OH formed in photolysis of H2o2 or in radiolysis of aqueous solution was well established for years. It was believed that the same radical 3 2 2 may be formed by reacting H2o2 with Ti +, Fe +, or Cr +. Nevertheless, many experimental results indicated, that OH is not formed in all these cases and we explained th~ reasons that earlier studies seemed to contradict this finding. 4+ We were also able to generate H0 2 from Ce and H2o2 and from excess of H2o2 with either Ti3+, Fe2+ or Cr 2+. The importance of these studies is in the ability to generate H0 2 and OH chemically. 10. USE OF FLOW METHODS FOR KINECTIC AND MECHANISTIC STUDIES The use of mixtures .. of Ti3+ and H o in flow systems was widely employed 2 2 in studies of radicals by ESR method. The method is based on f,lowing H2o2 with ·some solute ··RH and mixing it with Ti 3+ in front of and ESR cavity.
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