On the Chemical Yield of Base Lesions, Strand Breaks, and Clustered Damage Generated in Plasmid DNA by the Direct Effect of X Rays

Abstract Purkayastha, S., Milligan, J. R. and Bernhard, W. A. On the Chemical Yield of Base Lesions, Strand Breaks, and Clustered Damage Generated in Plasmid DNA by the Direct Effect of X Rays. Radiat. Res. 168, 357–366 (2007). The purpose of this study was to determine the yield of DNA base damages, deoxyribose damage, and clustered lesions due to the direct effects of ionizing radiation and to compare these with the yield of DNA trapped radicals measured previously in the same pUC18 plasmid. The plasmids were prepared as films hydrated in the range 2.5 < Γ < 22.5 mol water/mol nucleotide. Single-strand breaks (SSBs) and double-strand breaks (DSBs) were detected by agarose gel electrophoresis. Specific types of base lesions were converted into SSBs and DSBs using the base-excision repair enzymes endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg). The yield of base damage detected by this method displayed a strikingly different dependence on the level of hydration (Γ) compared with that ...