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In order to study the low-dose-rate effect of tritium beta-irradiation, we exposed single-stranded DNA of M13 mp10 phage to purified tritiated water. The beta-irradiated DNA was then transfected to E. coli K12 JM101. The lower the radiation dose rate, the more the transfection activity decreased. After the low-dose-rate effect was confirmed, the characteristics of tritiated water were also studied. The formation of an active oxidative species different from .OH, HO2., O2-., and H2O2 was found in the tritiated water by using UV spectrometry and luminescence measurement. Attributing it to nescent oxygen by reason of the production of the epoxide from mesityl oxide, we discussed the low-dose-rate effect from the viewpoint that the yield of the DNA modification could be relatively higher than that of the O2 formation in a competition reaction when the dose rate was lower. |
