28 - Verification of Two Different Hydroxyl Radical Densities in Aqueous Solution by Radiation

Abstract

Hydroxyl radical (●OH) is recognized a key player in biological effects of radiation. In this study, X-ray or heavy-ion beam induced ●OH generation was evaluated using fluorescent probe method. The eccentrically-located ●OH generations and the super-localized ●OH generations, which were previously reported based on EPR spin-trapping method, were again confirmed with a different types of analysis. Several concentrations (0.5-208 mM) of terephthalic acid disodium (TPA-Na) in aqueous solution were irradiated with 32 Gy X-ray or a heavy-ion beam (C400, Si490 or Fe500). The amount of ●•OH adduct of TPA-Na (hydroxyl terephthalate: hTPA) generated was measured by fluorophotometer (Ex.310 nm/Em. 425 nm). The relationship between the molecular density of TPA-Na in the reaction mixture and hTPA generated was analyzed. The amount of hTPA was increased in proportion to the molecular density of TPA-Na and reached plateau. The inflexion point was not changed by type of ray. The inflexion point suggests the relatively a concentration of ●OH generation. In the case of heavy-ion beam, another linear trend that passed through the origin was again observed when TPA-Na density was extremely high. This second linear increasing of hTPA suggested extremely dense generation of ●OH.