Radiation chemical mechanisms of single- and double-strand break formation in irradiated SV40 DNA
- Univ. of Pennsylvania School of Medicine, Philadelphia (USA)
Using an electrophoresis assay system developed in our laboratory, we have simultaneously measured single- and double-strand DNA breaks (SSBs and DSBs) induced by gamma radiation in small SV40 viral DNA molecules, under conditions of greatly varying radical scavenger concentration and DNA configuration. In our experiments with aqueous solutions of SV40 DNA, we observe that SSB induction is linear with dose (one-hit response), over the entire hydroxyl scavenger efficiency range examined, from approximately 0 to 5 x 10(9) s-1, while DSB induction shifts from having a major quadratic component (two-hit response) at very low scavenger efficiencies to nearly pure linear for efficiencies greater than 10(7) s-1. The mean ratio of SSBs to one-hit DSBs remains relatively constant with increasing scavenger efficiency, decreasing from about 100:1 to 40:1 as the scavenger efficiency increases from 2 x 10(5) s-1 to 5 x 10(9) s-1, and the absolute induction efficiencies for breaks decrease by three orders of magnitude. This decrease takes place primarily at scavenger efficiencies above 1 x 10(8) s-1. Irradiation of intranuclear SV40 minichromosomes induces SSBs and DSBs at nearly the same efficiencies as does irradiation of free DNA at the highest scavenger concentrations examined, and at only about twice the efficiencies observed at {minus}75{degree}C, where direct effects are believed to predominate. Our observations that the linear-quadratic mix of the dose-response curve for DSBs depends critically on scavenger efficiency may help to clarify the considerable confusion in the literature on the shape of such curves.
- OSTI ID:
- 5545771
- Journal Information:
- Radiation Research; (USA), Journal Name: Radiation Research; (USA) Vol. 126:2; ISSN 0033-7587; ISSN RAREA
- Country of Publication:
- United States
- Language:
- English
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Cells
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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKALI METAL ISOTOPES
AQUEOUS SOLUTIONS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CESIUM ISOTOPES
CHEMICAL RADIATION EFFECTS
DISPERSIONS
DNA
DOSE-RESPONSE RELATIONSHIPS
ELECTROMAGNETIC RADIATION
ELECTROPHORESIS
GAMMA RADIATION
GENETIC EFFECTS
GENETIC RADIATION EFFECTS
HYDROXYL RADICALS
IONIZING RADIATIONS
ISOTOPES
MICROORGANISMS
MIXTURES
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PARASITES
RADIATION EFFECTS
RADIATIONS
RADICALS
RADIOINDUCTION
SOLUTIONS
STRAND BREAKS
VIRUSES