Photosensitized inactivation of plasmid and bacteriophage lambda DNA: relative contribution to the lethal effect of monoadducts and diadducts of 8-methoxypsoralen and their repair in SOS-induced Escherichia coli cells

The curves of UV (254 nm)-inactivation and inactivation by furocoumarin derivatives + UVA radiation (PUVA) of bacteriophage lambda and biologically active plasmid pBR322 were measured using Escherichia coli K12 bacteria with different defects of DNA repair system as a ghost. The ratio of mono- and diadducts (interstrand cross-links) of 8-methoxypsoralen was determined that are formed after treating the DNA of pBR322 and bacteriophage lambda with PUVA. It is shown that, on the average, about five monoadducts per one diadduct are formed in DNA of pBR322, and about 0.9 monoadducts per one diadduct are formed in lambda phage DNA. An increased (up to 50%) efficiency of SOS-repair of monoadducts of 8-methoxypsoralen in DNA of pBR322 and lambda in the presence of plasmid pKM101 muc+ (incN) was found.