Analysis of DNA damage by soft X-ray spectroscopic method

Fujii, Kentaro; Yokoya, Akinari

Ionizing radiation produces various molecular damages on DNA through the energy deposition to matter. The activities of the repair enzymes could be modified with the chemical structure of DNA damages. We have investigated the radiation effects to DNA using "in situ" spectroscopic methods; mass analysis of the products induced by photo-desorption, spectroscopic analysis for X-ray absorption near edge structure, and the measurement of electron paramagnetic resonance to detected DNA radicals. These analyses enable us to open discussion the ion or radical reaction during irradiation and the reaction pathway to the final product of the DNA molecule. On the other hand, we used not only synchrotron soft X-rays, but also hard X-rays and heavy ions as radiation sources. Then we try to clarify the molecular changes by measuring X-ray absorption near edge structure (XANES) irradiated DNA molecules. The K-shell electrons of the element of DNA molecules can be ionized or excited by the soft X-rays. Therefore we can analyze functional groups appeared in DNA molecules irradiated. We used DNA or related molecules (deoxyribose, nucleobases and nucleotides), plasmid DNA (pUC18) and calf thymus DNA as irradiated samples. We will discuss the relationship between the DNA damage and radiation quality in respect of repairbility of damages.