Measurement of products from X-irradiated glycylglycine in oxygen-free aqueous solutions.

ABSTRACT

The product yields in X-irradiated aqueous solutions of glycylglycine (0.05 M and 1.0 M) were measured under deoxygenated conditions. Comparison was made between the results obtained from X- and 60Co gamma-irradiated glycylglycine solutions reported by Garrison, Sokol, and Bennett-Corniea (Radiat. Res. 53, 376-384, 1973). The mechanisms proposed by Garrison et al. were tested by evaluating the stoichiometric relationships. The two intermediate radicals, deamination and H-abstraction radicals, were produced in the initial interactions of glycylglycine with reactive species (e-aq, OH, H) formed in H2O. Although the difference was fairly large at 0.05 M, the production of deamination radicals agreed well with the consumption of the radicals at 1.0 M. The production and the consumption of H-abstraction radicals were within the estimated experimental error in dilute solutions. Among all the products only the G value of aspartic acid decreased with increasing concentration of glycylglycine. This could be attributed to the fact that more acetylglycine is formed at the expense of aspartic acid at 1.0 M than at 0.05 M glycylglycine solutions. Competitive reactions involved with deamination radicals under conditions of homogeneously distributed reactants are discussed to elucidate the radiation chemistry of glycylglycine.