Studies on Radiolysis of Amino Acids and Proteins III. On Radiolysis of Peptides and Proteins in Aqueous Solutions by Gamma Irradiation

Abstract

Several peptides and proteins were irradiated by γ-rays in aqueous solutions. Radiolytic deamination of peptides and related nitrogenous compounds were found to occur in the air-containing solutions by γ-irradiation. To the liberation of ammonia, not only free amino group but also peptide bond were proved to contribute. monia, not only free amino group but also peptide bond were proved to contribute. solutions by γ-irradiation. Moreover, in the course of radiolysis of the peptides, corresponding keto acids to constituent amino acids of peptides, were produced in the γ-irradiated peptide solutions. They were determined quantitatively by column chromatography of their 2, 4-dinitrophenylhydrazones. It was shown that aspartic acid formed from glycine in acetic acid solution by -irradiation under oxygen-free condition. To the mechanism of radiolysis of peptides and proteins, a valid evidence, that organic free radical produced by γ-irradiation might play an important role in the progress of reactions, was presented. From these facts, together with previous results, a scheme of radiolysis of proteins, was proposed and considered in discussion.