title: A novel technique using DNA denaturation to detect multiply induced single-strand breaks in a hydrated plasmid DNA molecule by X-ray and 4He2+ ion irradiation.
abstract: To detect multiple single-strand breaks (SSBs) produced in plasmid DNA molecules by direct energy deposition from radiation tracks, we have developed a novel technique using DNA denaturation by which irradiated DNA is analysed as single-strand DNA (SS-DNA). The multiple SSBs that arise in both strands of DNA, but do not induce a double-strand break, are quantified as loss of SS-DNA using agarose gel electrophoresis. We have applied this method to X-ray and (4)He(2+) ion-irradiated samples of fully hydrated pUC18 plasmid DNA. The fractions of both SS-DNA and closed circular DNA (CC-DNA) exponentially decrease with the increasing dose of X rays and (4)He(2+) ions. The efficiency of the loss of SS-DNA was half that of CC-DNA for both types of irradiation, indicating that one of two strands in DNA is not broken when one SSB is produced in CC-DNA by irradiation. Contrary to our initial expectation, these results indicate that SSBs are not multiply induced even by high linear energy transfer radiation distributed in both strands.
authors.affiliation: Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai-mura, Ibaraki 319-1195, Japan. yokoya.akinari@jaea.go.jp
authors.forename: Akinari
authors.initials: A
authors.lastname: Yokoya
authors.forename: Naoya
authors.initials: N
authors.lastname: Shikazono
authors.forename: Kentaro
authors.initials: K
authors.lastname: Fujii
authors.forename: Miho
authors.initials: M
authors.lastname: Noguchi
authors.forename: Ayumi
authors.initials: A
authors.lastname: Urushibara
mesh_terms: D004249:DNA Damage; D004587:Electrophoresis, Agar Gel / Q000379:methods*; D020450:Heavy Ions; D006371:Helium; D007554:Isotopes; D009691:Nucleic Acid Denaturation / Q000528:radiation effects; D010957:Plasmids / Q000737:chemistry* / Q000235:genetics / Q000528:radiation effects*; D011829:Radiation Dosage; D014965:X-Rays
chemical_list: D007554:Isotopes; D006371:Helium