Reverse Oxygen Effect on γ-Irradiation Induced
Single Strand Breaks of Plasmid DNA

SHAO Chun-Lin¹ , SAITO Masahiro² and YU Zeng-Liang¹
( ¹ Institute of Plasma Physics, Chinese Academy of Sciences, P O Box 1126, Hefei 230031, China；
² Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan )

Abstract　　 Oxygen effect on γ-irradiation induced single strand breaks (SSB) of plasmid DNA was measured by the method of gel scanning. It was found that, in the presence of mannitol, the yield of SSB in N₂-saturated DNA solution was larger than that in air-saturated solution so that the oxygen enhancement ratio (OER) of SSB became smaller than 1, which indicates the appearance of reverse oxygen effect of DNA SSB. At the same time, G(SSB) and its OER decreased with increasing concentration of mannitol.
Key Words　　γ-irradiation; DNA strand breaks; reverse oxygen effect

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