DNA damage induced by the direct effect of He ion particles

We present here evidence showing that the yields of DNA lesions induced by He(2+) ions strongly depend on Linear energy transfer (LET). In this study, hydrated plasmid DNA was irradiated with He(2+) ions with LET values of 19, 63 and 95 keVmicrom(-1). The yields of prompt single-strand breaks (SSBs) are very similar at the varying LET values, whereas the yields of prompt double-strand breaks (DSBs) increase with increasing LET. Further, base lesions were revealed as additional strand breaks by post-irradiation treatment of the DNA with endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg). The reduction in the yield of these enzymatically induced SSBs and DSBs becomes significant as the LET increases. These results suggest that the clustering of DNA lesions becomes more probable in regions of high LET.