Quantitation of thymine radiolysis products in DNA x-irradiated in vitro

High or low concentrations of PM2 DNA were x-irradiated either in Tris-EDTA or in phosphate buffer in air. After irradiation, DNA damage was monitored simultaneously by the anti-thymine glycol (anti-TG) antibody assay as well as the Escherichia coli endonuclease III (endo III) nicking assay. When PM2 DNA was x-irradiated in air in Tris-EDTA at high concentrations, a dose dependent increase of anti-TG binding sites, acetol fragments, and endo III sensitive sites were observed. When PM2 DNA was irradiated in air in phosphate buffer, both the number of acetol fragments and endo III sensitive sites were 5 to 10 fold higher than the number observed when the DNA was irradiated in Tris-EDTA. The authors are presently corroborating these results by HPLC analysis of the products released after endo III digestion of x-irradiated DNA. The implications of these data with respect to thymine glycol production are discussed