MECHANISMS OF RADIATION-CHEMICAL REACTION IN BIOCHEMICAL SYSTEMS

摘要

Current concepts related to mechanism in the radiolysis of aqueous amino acids and peptides are reviewed. Emphasis is given to recent studies of the peptide linkage as a locus of indirect action. It is shown that radiolytic reactions of protein, both in oxygenated and in oxygen-free solutions, lead under appropriate conditions to cleavage of the polypeptide chain. Reaction in oxygenated solution corresponds to a radiation-induced step that gives rise to amide and carbonyl terminal functions at the locus of cleavage. In oxygen-free solutions, cleavage occurs predominantly through postirradiation hydrolysis of acyl imino linkages (-CO-N = C(R) -) to give essentially the same final products. Observed differences in the rates of the postirradiation liberation of ammonia for the two cases support the mechanisms proposed.