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 Science and Technology.
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Presence of high concetntrated hydrogen peroxide (H2O2) clusters in an aqueous solution during X-ray irradiation was demonstrated. A method to measure the distance between the clusters was attempted. X-ray induced H2O2 generation in the sample solution is related to the hydrogen-donor-independent reduction of nitroxyl radical, however the reaction mechanisms are still in progress. In this study, the relation of H2O2 concentraion and hydrogen-donor-independent reduction of nitroxyl radical was tested, and then the distance between localyzed H2O2 clusters was estimated.
Reaction mixtures containing 0.1 mM of a nitroxyl redox probe, TEMPOL or Carbamoyl-PROXYL, were prepared with containing several different concentrations (1.0 mM‒9.8 M) of H2O2. The reaction mixture was irradiated by 12000 μW/cm2 UVB for 2 min, and the reduction of the EPR signal of the nitorxyl radical was measured. An aliquot (2 µL) of 200 mM K3[Fe(CN)6] solution was added to 200 µL of the reaction mixture, and the time course of the EPR signal of the nitorxyl radical was measured. A series of nitroxyl radical solutions with several different concentrations (0.06 μM‒2.28 mM) was irradiated with X-ray, and then the amount of reduction of nitroxyl radical in each sample was measured by EPR.
The UV induced EPR signal loss of the nitorxyl radical was increased with H2O2 higher than 10 mM. The EPR signal of nitorxyl radicals were decreased in the solution containing 1 M of H2O2, when K3[Fe(CN)6] was added to the reaction mixture. Oxidative stimulation by UVB irradiation or addition of K3[Fe(CN)6] could cause nitorxyl radical reduction in a high concentration H2O2 environment. This result suggests that ionizing radiations could prepare a high concentration H2O2 environment, which may be localized. Plotting reduction amount with density of nitroxyl radical showed that the high concentration H2O2 clusters are with 43‒44 nm separation.
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)
Presence of X-ray induced high concentrated hydrogen peroxide clusters
