Host: The Japan Radiation Research Society
Co-host: Asian Association for Radiation Research
DNA damages induced by ionizing radiation are characterized as base modifications, DNA strand breaks and cross-linkings. Most of the DNA damages mentioned above are induced by hydroxyl radicals. Hydroxyl radicals are thought to attack mainly DNA bases but about one fifth of it attacks the DNA backbone to produce the scissions of deoxyribose-phosphate bonds. DNA double strand break may cause genome instability, cell death and carcinogenesis. Studies of the mechanisms of DNA double strand break are one of the most important subjects to clarify the DNA damage induced by ionizing radiation.Recently we could control DNA structures and make compact folded DAN and stretching unfolded DNA by addition of polyamine compounds. In this experiment, we used T4 DNA and made two structures, folded and unfolded DNA by adding spermidine. DNA solutions having different DNA structures were irradiated by cobalt-60 gamma radiation, and DNA double strands breaks were estimated by fluorescence microscopic measurement.For the estimation of DNA double strand breaks, we used two different techniques. One is the direct measurement of DNA length absorbed on the glass and another is an indirect method to estimate DNA length by observation of hydrodynamic radius moving in water by Brawnian movement.In our presentation, we will mention the technical details of our experiments, and relationships between the higher-order structure of DNA molecules and DNA damage by ionizing radiation.
