title: The effect of superhelical density on the yield of single-strand breaks in gamma-irradiated plasmid DNA.
abstract: Using agarose gel electrophoresis, the formation of DNA single-strand breaks (SSBs) by 137Cs gamma irradiation was quantified in negatively supercoiled topological isomers of plasmid pUC18. The G value for SSB formation falls slightly from 1 x 10(8) to 8 x 10(-9) SSB Gy-1 Da-1 as the superhelical density varies from 0.00 to -0.08. This result is not in agreement with recent observations by others which suggest that increasing the negative superhelical density of plasmid DNA increases its sensitivity to X irradiation.
authors.affiliation: Department of Radiology, University of California at San Diego, La Jolla 92093-0610.
authors.forename: J R
authors.initials: JR
authors.lastname: Milligan
authors.forename: A D
authors.initials: AD
authors.lastname: Arnold
authors.forename: J F
authors.initials: JF
authors.lastname: Ward
mesh_terms: D002588:Cesium Radioisotopes; D004249:DNA Damage; D004269:DNA, Bacterial / Q000528:radiation effects*; D004277:DNA, Single-Stranded / Q000528:radiation effects*; D004278:DNA, Superhelical / Q000528:radiation effects*; D005720:Gamma Rays; D010957:Plasmids
chemical_list: D002588:Cesium Radioisotopes; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004278:DNA, Superhelical