T2 phage sensitization by linear and angular furocoumarins.

T2 bacteriophage sensitization has been studied using two furocoumarins capable of linking covalently to DNA to the same extent but producing different damages, psoralen and 4,5'-dimethylangelicin. Psoralen is a well-known linear furocoumarin capable of inducing in DNA both monoadducts and cross-links; 4,5'-dimethylangelicin is a new angular compound known as a pure monofunctional reagent. In the sensitization of T2 mature virions both drugs proved very active, yielding survival curves practically superimposable; on the contrary, in the experiments with the T2 vegetative form, i. e. its DNA inside the host, 4,5'-dimethylangelicin resulted much less effective, resembling the picture observed in the inactivation of the host bacteria. This result did not appear related to an enhancement of DNA repair by a Weigle effect. The different killing activity of 4,5'-dimethylangelicin can be explained supposing that this drug is capable of inducing cross-links in T2 DNA inside the virus core, in which it exists in a very folded form, but not in the same DNA after injection into the host bacteria.