Photochemistry of dipeptides in aqueous solution

The photochemical lability of peptides is poorly understood, largely because of the lack of product data. In the present study, product analyses have been carried out following the photolyses in aqueous solution of selected glycyl dipeptides (Gly-Gly, DL-AIa-GIy, L-VaI-GIy, L-Pro-Gly, L-Phe-Gly, and Gly-L-Phe), L-prolyl-L-phenylalanine, and L-phenylalanyl-L-proline. Efficient deamination and decarboxylation of aliphatic dipeptides generate thermal precursors of simple amides in a photoinduced electron-transfer process involving the peptide bond. An analogous pathway in the photodegradation of phenylalanyl peptides suffers competition from other types of reaction.