Near-UV photoproduct(s) of L-typtophan: an inhibitor of medium-dependent repair of X-ray-induced single-strand breaks in DNA which also inhibits replication-gap closure in Escherichia coli DNA.

Near-UV photoproducts of L-tryptophan (TP), which are especially toxic for recombination-deficient (rec) mutants, were found to inhibit medium-dependent repair of X-ray-induced single-strand breaks. This inhibitor also slows the rate of closure of replication gaps, suggesting that these two processes may have a common pathway (or share a required step which TP can inhibit).