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 <tex-math>$\dot{{\rm C}}{\rm H}_{3}$</tex-math>, the formyl radical ĊHO, the imino radical <tex-math>$\dot{{\rm N}}{\rm CH}_{2}$</tex-math>, and a radical <tex-math>$({\rm NH}_{2}){\rm CH}R-{\rm CONH}-\dot{{\rm C}}R-{\rm COOH}$</tex-math> 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 reptured.

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