X- and γ-radiolysis of Some Tryptophan Dipeptides

Abstract

Irradiation of the dipeptides tryptophyl-glycine, -alanine, -leucine, -tryptophan, -tyrosine, and -phenylalanine in aerated solution gave essentially the same products in each case. The major products are those known to arise from the radiolysis of tryptophan, which is therefore proposed as the initial product of hydroxyl radical attack on the α-carbon atom adjacent to the peptide nitrogen. The presence of an aromatic ring in the C-terminal acid (try-tyr, try-phe) results also in hydroxyl radical attack on this ring. Results agree qualitatively with the mechanisms proposed for peptide radiolysis by Liebster and Kopoldova (1966) and Garrison (1968).