ESR studies on the direct photolysis of aliphatic dipeptides

The direct photolysis of aqueous solutions of aliphatic dipeptides leads to the formation of different types of radicals. Depending on the temperature range the most characteristic ones are the methyl radical CH3, the formyl radical CHO, the imino radical NCH2, and a radical (NH2)CHR--CONH--CR--COOH formed by hydrogen atom abstraction. The possible mechanisms of the formation of the radicals are discussed. It is suggested that in dipeptides bonds are broken in various parts of the molecules as a consequence of direct photolysis. In particular, the peptide bond seems to be ruptured