NEAR‐UV‐INDUCED BREAKS IN PHAGE DNA: SENSITIZATION BY HYDROGEN PEROXIDE (A TRYPTOPHAN PHOTOPRODUCT)

Abstract

Abstract— Near‐UV irradiation of l ‐tryptophan yields a large number of photoproducts. When this mixture is added to recombinationless ( rec ) mutants of bacteria, the cells are killed. The most toxic component of tryptophan photoproducts has been identified as hydrogen peroxide (H 2 O 2 ). We now report that both tryptophan photoproducts and H 2 O 2 sensitize phage DNA to near‐UV radiation resulting in enhanced killing as well as enhanced DNA breakages. We conclude that the in situ production of H 2 O 2 via tryptophan photolysis may be an important biological event.