A Novel technique using DNA denatureation to detect multiplly induced single-strand breaks in a hydrated plasmid DNA molecule by X-ray and He ion irradiation

Yokoya, Akinari; Shikazono, Naoya; Fujii, Kentaro; Noguchi, Miho; Urushibara, Ayumi

Multiple single-strand breaks (m-SSBs), which are predicted to be preferentially induced by high LET radiation, would be underestimated if one uses the conventional method using plasmid DNA, because m-SSBs will not cause additionally conformational changes if they are on the same or on the opposite strand but separated each other sufficiently so as not to induce a double strand break. In order to observe the invisible m-SSBs, we have developed a novel technique using DNA denaturation. The m-SSBs arising in both strands of DNA are revealed as molecular size change in single strand DNA (SS-DNA) by gel electrophoresis. We have applied this method to the X- and He ion irradiated sample of hydrated pUC18 plasmid DNA. A half of SS-DNA population remains as intact within the experimental resolution ( 140 bases) for both irradiations. Contrary to our initial expectation, these results indicate that SSBs are not multiply induced over 140 bp even by high-LET irradiation.