title: [Plasmid DNA strand breaks induced by laser irradiation of 193 nm wavelength].
abstract: DNA of plasmid pBR322 irradiated with laser at a wavelength of 193 mm was treated with an extract containing proteins from E.coli K12 AB1157 (wild-type). The enzymes were found to produce single- and double-strand DNA breaks, which was interpreted as a transformation of a portion of cyclobutane pyrimidine dimers and (6-4) photoproducts into nonrepairable single-strand DNA breaks. The products resulted from ionization of DNA, in particular, single-strand breaks, transform to double-strand breaks. A comparison of these data with the data on survival of plasmid upon transformation of E.coli K12 AB1157 enables one to assess the biological significance of single- and double-strand breaks. The inactivation of the plasmid (in AB1157) is mainly determined by the number of directly formed laser-induced single-strand breaks, whereas the contribution of enzymatically produced single- and double-strand breaks is insignificant.
authors.affiliation: Max-Planck Institute of Radiation Chemistry, Mühlheim-on-Ruhr, Germany.
authors.forename: G G
authors.initials: GG
authors.lastname: Gurzadian
authors.forename: D
authors.initials: D
authors.lastname: Schulte-Frohlinde
mesh_terms: D004249:DNA Damage; D004269:DNA, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D007834:Lasers; D010957:Plasmids / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial