title: Efficiencies of induction of DNA double strand breaks in solution by photoabsorption at phosphorus and platinum.
abstract: OBJECTIVE
  This paper aims at determining and comparing the cross sections and quantum yields for DNA strand break induction by the Auger effect at the K-shell of phosphorus and at the LIII-shell of platinum.
  
  
  METHODS
  Using synchrotron radiation, free and Pt-bound pBR322 plasmid DNA were irradiated in solution with monochromatic X-rays, the energies of which were 2.153 and 2.147 keV, corresponding to "on" and "below" the phosphorus K-shell photoabsorption, and 11.566 and 11.542 keV for "above" and "below" the L(III)-shell photoabsorption of platinum, respectively. To suppress indirect effects by hydroxyl radicals, DMSO (1M) was used as a scavenger.
  
  
  RESULTS
  The inner-shell photoabsorption of phosphorus and of platinum significantly increased the induction of DNA double strand breaks (DSB), whereas it had little effect on single strand break (SSB) induction. The quantum yields for the induction of DSB were calculated to be 0.017 and 1.13, in the case of phosphorus and platinum, respectively. CONCLSIONS: The value of the quantum yield for the DSB induction of platinum was about 66-fold larger than that for the phosphorus. These results clearly demonstrate that the quantum yield of DSB depends upon the magnitude of the Auger cascade.
authors.affiliation: Department of Materials Structure Science, School of High Energy Accelerator Science, The Graduate University for Advanced Studies, 1-1 Oho, Tsukuba-shi, Ibaraki 305-0801, Japan. mmaeda@post.kek.jp
authors.forename: Munetoshi
authors.initials: M
authors.lastname: Maeda
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kotaro
authors.initials: K
authors.lastname: Hieda
mesh_terms: D004247:DNA / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D004583:Electrons; D018499:Linear Energy Transfer; D015336:Molecular Probe Techniques; D010758:Phosphorus / Q000737:chemistry / Q000528:radiation effects*; D010984:Platinum / Q000737:chemistry / Q000528:radiation effects*; D011829:Radiation Dosage; D012996:Solutions; D014965:X-Rays
chemical_list: D012996:Solutions; D010758:Phosphorus; D010984:Platinum; D004247:DNA; C427203:calf thymus DNA