KINETICS OF PROrARY REACTIONS AND CHEMICAL 



PROTECTION 



V. N. TARUSOV 

 Biulvgiad Departint)d, Moscow State University, Moscow, U.S.S.R. 



SUMMARY 



The kinetics of the i)rotective reaction of anti-oxidizing agents was studied in 

 order to analyse the mechanisms of the primary reactions. New facts have been 

 adduced which testify to the chain mechanism of radiochemical oxidizing reac- 

 tions induced by radiation. It has been established that chemical protection is 

 afforded not only when the oxygen level is reduced but also when the pressure is 

 raised above a certain critical level which is the characteristic property of oxidizing 

 reactions of the chain type, with branched chains. 



It has been established that the kinetics of the variation of the amoimt of 

 lii:)oiDeroxides in the tissues of irradiated organisms corresponds to the formula 

 for the accumulation of intermediate products of branched chain reactions. But 

 the kinetics for the variation in unsaturated fatty acids is analogous to the 

 kinetics for the accumulation of the final products in branched chain reactions. 



The presence of chain oxidizing reactions is confirmed by the discovery of 

 very weak luminescence in the region of 4,000 A to 5,200 A which increases con- 

 siderably lander irradiation conditions. 



The quantitative analysis of the data concerning the protective action of in- 

 creased oxygen and of anti-oxidants has shown that these factox's are inhibitors 

 of oxidative chain reactions in cell lipids. It has also been shown that the action 

 of anti-oxidants is restricted and in the most favourable conditions they cannot 

 absorb more than 50 per cent of the dose. This incomplete lorotection shows that 

 the oxidation chain reactions are not the sole primary reactions and apart from 

 them there arise, and are developed, non-oxidative reactions in various biological 

 substrata. Investigations have shown that this is mainly a reaction of an auto- 

 lytic character which develops after irradiation. The protective substances which 

 contain — SH groups activate this type of reaction. The investigations were 

 carried out in yeast of haploid and diploid strains, in mice and in rats. 



Ionizing radiations, with strong chemical action, lead to the for- 

 mation of radicals and ions. An essential part is played by those that 

 can induce primary radiochemical reactions developing after irradia- 

 tion, and involving a great number of molecules per single ionizing 

 event. 



It is very difficult to establish the nature of primary chemical reac- 

 tions on the basis of chemical changes in cells and tissues alone, as the 

 concentration of the products of primary reactions is very low and lies 



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