@misc{oai:repo.qst.go.jp:00070092,
 author = {Matsumoto, Kenichiro and Nakanishi, Ikuo and Anzai, Kazunori and 松本 謙一郎 and 中西 郁夫 and 安西 和紀},
 month = {May},
 note = {A paramagnetic nitroxyl radical was oxidized by superoxide (•O2-) or hydroxyl radical (•OH) to give the oxoamonium cation. The oxoamonium cation reacts with glutathione to make a stable diamagnetic compound (structure unidentified) or with NAD(P)H to become the hydroxylamine. The hydroxylamine can be re-oxidized mainly by •OH to give the corresponding nitroxyl radical. Hydrogen peroxide (H2O2) participates a reducing the nitroxyl radical during high dose irradiation, since this reduction of nitroxyl radical was restrained by catalase. In this study, amount and distribution of several ROS generated in a gelatin sample by carbon ion irradiation was estimated using a nitroxyl radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL), or its hydroxylamine form, i.e. TEMPOL-H as a redox probe.
The reduction of TEMPOL in a reaction mixture containing a combination of TEMPOL and GSH can be an index of total reaction of ROS (mainly •OH and •O2-). The GSH-independent reduction of nitroxyl radical caused by high dose irradiation in a reaction mixture of TEMPOL alone can be an index of H2O2 generation. The oxidation of TEMPOL-H in a reaction mixture containing TEMPOL-H alone can be an index of OH. Each reaction mixture containing 0.1 mM TEMPOL or TEMPOL-H was caked using gelatin to test depth-dependent redox reactions. The gelatin sample was irradiated with a 290 MeV/nucleon carbon ion beam at a dose of 32 Gy with several different linear energy transfer (LET) setting. An aliquot of gelatin sample was sampled from surface using a glass capillary, and then increase or decrease of TEMPOL signal was measured by X-band EPR spectrometer.
Amount of GSH-dependent reduction of TEMPOL was 400–1200 nmol/L/Gy, which decreased with increasing LET. Amount of GSH-independent reduction of TEMPOL was 30–300 nmol/L/Gy, which also decreased with increasing LET. The level of 30–300 nmol/L/Gy GSH-independent reduction of TEMPOL was estimated as around 60–600 nmol/L/Gy of H2O2 generation if it was simply correlated with X-ray. Amount of oxidation of TEMPOL-H was 2–4 nmol/L/Gy, which also decreased with increasing LET. This result is suggesting that •O2- and/or H2O2 may be an important species to regulate at lower LET part, which usually corresponds to a normal tissue at the carbon ion cancer therapy., EPR 2010 (A Joint Conference of the 14th In Vivo EPR Spectroscopy and Imaging and the 11th International EPR Spin Trapping/Spin Labeling)},
 title = {Reactive Oxygen Species Generated in an Aqueous Gelatin Sample Irradiated by Carbon Ion Beam},
 year = {2010}
}