Journal of Clinical Biochemistry and Nutrition
Online ISSN : 1880-5086
Print ISSN : 0912-0009
Original Articles
Localized hydroxyl radical generation at mmol/L and mol/L levels in water by photon irradiation
Yukihiro OgawaEmiko Sekine-SuzukiMegumi UenoIkuo NakanishiKen-ichiro Matsumoto
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2018 Volume 63 Issue 2 Pages 97-101

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Abstract

The generation of localized hydroxyl radical (OH) in aqueous samples by low linear energy transfer irradiation was investigated. Several concentrations of 5,5-dimethyl-1-pyrroline-N-oxid solution (from 0.5 to 1,680 mmol/L) were prepared and irradiated with an identical dose of X-ray or γ-ray. The density of OH generation in aqueous solution was evaluated by the electron paramagnetic resonance spin-trapping technique using 5,5-dimethyl-1-pyrroline-N-oxid as an electron paramagnetic resonance spin-trapping agent. The relationship between the molecular density of 5,5-dimethyl-1-pyrroline-N-oxid in the samples and the concentration of 5,5-dimethyl-1-pyrroline-N-oxid-OH generated in the irradiated samples was analyzed. Two different characteristic linear trends were observed in the 5,5-dimethyl-1-pyrroline-N-oxid-OH/5,5-dimethyl-1-pyrroline-N-oxid plots, which suggested OH generation in two fashions, i.e., mmol/L- and mol/L-level local concentrations. The dose, dose rate, and/or the energy of photon irradiation did not affect the shapes of the 5,5-dimethyl-1-pyrroline-N-oxid-OH/5,5-dimethyl-1-pyrroline-N-oxid plots. Moreover, the addition of 5 mmol/L caffeine could cancel the contribution of mmol/L-level OH generation, leaving a trace of mol/L-level OH generation. Thus, the localized mmol/L- and mol/L-level generations of OH, which were independent of experimental parameters such as dose, dose rate, and/or the energy of photon of low linear energy transfer radiation, were established.

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