Conformational change of giant DNA induced by ascorbic acid 2-glucoside in relation to radiosensitivity

We performed single-molecule observation of DNA double-strand breaks caused by Co60 γ-ray irradiation and quantitatively evaluated the protective effect of ascorbic acid 2-glucoside (AA-2G). AA-2G is a stable derivative of ascorbic acid. We found that AA-2G induces a significant conformational change on DNA. We also evaluated the protective effect of AA-2G against radiation-induced DNA double-strand breaks in a quantitative manner. To analyze the efficiency of the breakage reaction on individual DNA molecules, we used a large DNA, T4 phage DNA (166 kbp). The irradiation dose was varied up to 200 Gy. We measured the full length of individual DNA molecules fixed on glass surface after irradiation. Results revealed that DNA damage was reduced one-third when DNA was compacted by 4 mM of AA-2G.