Research on the chemical processes of nucleotide damage using soft x-ray irradiation

The radiation damages of DNA in a living thing are recognized in general that hydroxyl radicals in water, which are produced by direct effects of the radiation energy to water molecules, act indirectly on the DNA. The chemical processes on the DNA damage in aqueous solution are studying with a particular soft x-ray which penetrates water without producing the hydroxyl radicals, but acts exactly on nitrogen molecules in the DNA. A nitrogen oscillation light (wave length 3.3 nm, energy 381eV) has a possibility for the particular soft x-ray in threshold region of water. The threshold region soft x-ray source has been developed by using nitrogen cryo-gas as a target and a laser apparatus for excitation of the nitrogen, although the experiments for generating the particular soft x-ray are not accomplished yet. Radiation effects on adenine nucleotiode aqueous solution are studying also. Analytic conditions of oligo-adenylic acid homo polymer sample in aqueous solution are investigated by high speed liquid chromatography. A minute change of the oligo-adenylic acid following x-ray irradiation could be traced. Infrared- and ultraviolet-spectroscopy are also useful for the analysis of adenine content in aqueous solution. (M. Suetake)