Photolesions and biological inactivation of plasmid DNA on 254 nm irradiation and comparison with 193 nm laser irradiation

Plasmid pTZ18R and calf thymus DNA in aerated neutral aqueous solution were irradiated by continuous 254 nm light. The quantum yields are φssb = 4.0 x 10-5 and φdsb = 1.4 x 10-6 for single- and double-strand break formation, respectively, φbr = 2.3 x 10-5 for base release, φdn = 2.1 x 10-3 for destruction of nucleotides, and φicl ∼ φids ∼ 1 x 10-6 for interstrand cross-links and locally denatured sites, respectively. The corresponding φ values, obtained on employing pulsed 193 nm laser irradiation, are much larger than those using λirr = 254 nm. (Author)