Protective behavior of tea catechins against DNA double strand breaks produced by radiations with different linear energy transfer

The number of DNA double strand breaks (DSBs) of genome-sized DNA was quantitatively evaluated under several types of radiation sources. The characteristics of radiation damages by different linear energy transfer (LET) and the effect of radiation protection by tea catechins were also studied as a function of its concentration. After β-rays and γ-rays irradiation to samples, the length of genome size DNA molecules (bacteriophage T4 GT7 DNA; 166 kbp) was measured by single molecule observation method using fluorescence microscope, which can estimate DSBs quantitatively. It was found that the number of DSBs was increased with increasing LET due to high radical density. By addition of EGCg ((-)-epigallocatechin gallate), the number of DSBs was reduced with a small concentration of 1 µM.