Nucleobase lesions and strand breaks in dry DNA thin film selectively induced by monochromatic soft X-rays

単色軟X線により選択的に乾燥DNA薄膜に誘発される塩基損傷と主鎖切断

藤井 健太郎; 鹿園 直哉; 横谷 明徳

Fujii, Kentaro; Shikazono, Naoya; Yokoya, Akinari

軟X線によって乾燥プラスミドDNA中に生じる分子主鎖切断や酸化的塩基損傷の収率をアガロース電気泳動法により検出した。塩基損傷の検出は、照射試料を塩基除去修復酵素で処理することによって塩基損傷を鎖切断に変換することで定量した。それぞれの収率は、軟X線のエネルギーに依存し、特に酸素K殻吸収によって鎖切断及び塩基損傷の収率の有意な増加が見られた。

In order to verify the possibility of selective damage induction in DNA, the yields of base lesions as well as strand breaks have been measured in dry plasmid DNA films irradiated with highly monochromatized soft X-rays in the energy region of 270-760 eV, which includes the carbon, nitrogen and oxygen K-edges. Our results strongly suggest that (1) the K-shell ionization of oxygen in both the nucleobases as well as in other parts of DNA and in the hydrating water molecules bound to DNA, but not the K-shell ionization of nitrogen in the nucleobases, most likely contributes to the induction of nucleobase lesions, and (2) migration of electrons and holes are involved differentially in the production of each type of DNA lesion. These results could potentially lead to new methods for selective induction of specific types of DNA damage through tuning the energy of soft X-rays.