Formation of multiple DNA damage by indirect effects

Kai, Takeshi   ; Toigawa, Tomohiro   ; Matsuya, Yusuke*  ; Hirata, Yuho   ; Tsuchida, Hidetsugu*; Yokoya, Akinari*

This review introduces a chemical calculation code which can quantitatively evaluate the indirect effects of DNA damage. Radiation DNA damage is formed from direct and indirect effects. The direct effect is the interaction between DNA and a radiation, while the indirect effect is the chemical reaction between DNA and radiolytic chemical species. The damage reduces repair efficiency and induces biological effects. In this study, DNA damage induced by only indirect effects was quantitatively evaluated. Our results indicated that the multiple damage is formed when only tens of eV energy is deposited to water in the vicinity of DNA, although its formation probability is less than 1%. In other words, the possibility of late biological effects cannot be excluded by imparting energy to water in the extreme vicinity of DNA. Our results are one of the most important findings for understanding low-dose radiation risk.