ON THE MODE OF ACTION OF X-RAY PROTECTIVE AGENTS

Abstract

The interaction of thiols with disulfides is generally looked upon as a reversible oxidation-reduction reaction, formulated as in Equation 1. 2XSH + YSSY ti XSSX + 2YSH(1)Evidence indicates that the reaction actually proceeds according to Equations 2 and 3, with the intermediary formation of a mixed disulfide (1).It is generally assumed that in equilibrium mixtures the mixed disulfides exist only in catalytic amounts which can be safely neglected in biochemistry.However, recently we were able to isolate substantial amounts of mixed disulfides when cystamine was allowed to interact, in tivo or in vitro, with the SH groups of proteins and simple thiols (24).Simultaneously Kolthoff et al. ( 5) have studied the interaction of cystine with thioglycolic acid and with glutathione by measuring the increased solubility of cystine in the presence of other thiols and disulfides.By this indirect method they obtained the appropriate equilibrium constants K2 and KS which indicate, as will be shown below, t,he existence of large equilibrium concentrations of mixed disulfides in these systems as well.In the present study of thiol-disulfide interactions procedures have been developed which permit, in general, detailed studies of the chemistry of mixed disulfide formation.The met.hod involves the isolation and direct

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Affiliated Institutions

• Norwegian Cancer Society

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