title: ESR spin trapping of hydroxyl radicals in aqueous solution irradiated with high-LET carbon-ion beams.
abstract: The aim of this study was to quantify the hydroxyl radicals (*OH) produced when aqueous solutions are decomposed by high-linear energy transfer (LET) 290 MeV/nucleon carbon-ion beams using an electron spin resonance (ESR) spectrometer. Aerated cell culture medium containing 200 mM 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was irradiated with doses of 0 to 20 Gy with an LET of 20 to 90 keV/ micro m. We were able to obtain ESR spectra 10 min after irradiation, and the formation of *OH and hydrogen atoms was confirmed by radiolysis of deuterium oxide and ethanol containing DMPO. Our results showed that the yield of *OH by carbon-ion radiolysis increased in proportion to the absorbed dose over the range of 0 to 20 Gy. Furthermore, we discovered that the yield of *OH decreased linearity as LET increased logarithmically from 20 to 90 keV/ micro m. The generation of *OH by carbon-ion radiolysis at LETs of 20, 40, 60, 80 and 90 keV/ micro m was 64, 58, 52, 49 and 50%, respectively, of that for low-LET X radiolysis. These unique findings provide a further understanding of the indirect effect of high-LET radiation.
authors.affiliation: Department of Neurosurgery, Institute of Clinical Medicine, University of Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Moritake
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuboi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Anzai
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ozawa
authors.forename: Koichi
authors.initials: K
authors.lastname: Ando
authors.forename: Tadao
authors.initials: T
authors.lastname: Nose
mesh_terms: D002244:Carbon; D004578:Electron Spin Resonance Spectroscopy; D017665:Hydroxyl Radical / Q000032:analysis*; D018499:Linear Energy Transfer; D011829:Radiation Dosage; D012996:Solutions
chemical_list: D012996:Solutions; D017665:Hydroxyl Radical; D002244:Carbon