量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Hydrogen radicals (·H) generated during irradiation of X-ray to aqueous solutions were quantified by an electron paramagnetic resonance (EPR) spin-trapping technique using a spin-trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). It has been reported that generation of hydroxyl radicals (·OH) that could be spin-trapped by DMPO were localized and observed as two different densities i.e. molar and millimolar levels. When ·OH are generated with the decomposition of water molecules, simultaneous generation of ·H is expected. Although ·H were quite important reactive species to generate superoxide by reacting with oxygen, almost nothing has been reported about the density of ·H generation caused in aqueous solutions by radiation.
X-ray was irradiated to a series of DMPO aqueous solutions (1.7 mM-1700 mM) with a dose of 8 Gy, 16 Gy, or 32 Gy at a dose rate of approximately 3.0 Gy/min. Signal intensities of DMPO-OH and DMPO-H was measured by X-band EPR spectrometer. The second line from the lower end of the magnetic field of DMPO-OH spectrum, which comprises the characteristic 1:2:2:1, and the middle line of DMPO-H spectrum, which comprises the characteristic 1:1:2:1:2:1:2:1:1 were recorded. The inverse of the intermolecular distance of DMPO was taken as the density (100 µm-1-1000 µm-1). The profiles plotting concentrations of DMPO-OH or DMPO-H against the DMPO density were compared between DMPO-OH and DMPO-H.
When the DMPO density was less than 200 µm-1, a step increasing of the DMPO-OH was observed, then plateau was come out, again linear increasing was obtained. This result was well agreed with the previous reports. DMPO-H showed an almost similar profile with DMPO-OH, except the variations of DMPO-H values were huge. It was demonstrated that ·OH and ·H were generated as the same time and showed similar density profiles.
会議概要（会議名, 開催地, 会期, 主催者等）
The Society for Redox Biology and Medicine's 26th Annual Conference (SfRBM 2019)
Quantification of X-ray induced hydrogen radicals in an aqueous solution using EPR spin-trapping
