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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The reactivity of nitroxyl free radicals with reactive oxygen species (ROS) were compared. Here, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) and 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (CmP) were tested as typical 6-membered and 5-membered ring nitroxyl compounds. The hydroxyl amin forms of the both nitroxyl radicals, i.e. TEMPOL-H and CmP-H, were also tested. Two free radical species of ROS, i.e. hydroxyl radical (•OH) and superoxide (O2•-), were subjected to a competition. •OH was generated by UV irradiation from an aqueous H2O2 solution (H2O2-UV system). O2•- was generated by a reaction of hypoxanthine and xanthine oxidase (HX-XO system). The amounts of generated ROS, i.e. •OH generated by the H2O2-UV system or the O2•- by the HX-XO system, were quantified by electron paramagnetic resonance (EPR) spin-trapping, and were adjusted to be similar. The time courses of one-electron oxidation of TEMPOL, CmP, TEMPOL-H, and CmP-H in each ROS generation system were observed and compared. TEMPOL was more oxidized in the HX-XO system than in the H2O2-UV system, while CmP was more oxidized in the H2O2-UV system than in the HX-XO system. The hydroxylamine form of nitroxyl radicals, i.e. TEMPOL-H and CmP-H, were similary oxidized eather in the H2O2-UV system or the HX-XO system, while the CmP-H was almost 3 times more oxidized compare to TEMPOL-H.
Reactivity of Redox Sensitive Paramagnetic Nitroxyl Contrast Agents and Reactive Oxygen Species
