title: Detection of free radical reactions in an aqueous sample induced by low linear-energy-transfer irradiation.
abstract: Quantitative detection of free radical reactions induced by low linear-energy-transfer (LET) irradiation in an aqueous solution was attempted using nitroxyl radicals. The stability and reactivity of reaction mixtures containing a nitroxyl radical and a hydrogen donor, i.e., glutathione (GSH), nicotinamide adenine dinucleotide (NADH), or nicotinamide adenine dinucleotide phosphate (NADPH), were tested. X-band electron paramagnetic resonance (EPR) measurements of several reaction mixtures were performed to find a suitable preparation to quantitatively detect free radical reactions produced by low LET irradiation. The EPR signal intensity of nitroxyl radicals was decreased by low LET irradiation when a hydrogen donor coexisted in the reaction mixture. The combination of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (4-hydroxy-TEMPO, known as TEMPOL) and GSH was most preferable among other preparations tested in this paper, because of the sensitivity and irreversible reaction. The extent of the free radical reaction, i.e., formation of reactive oxygen species, in the reaction mixture depended on the radiation energy when an identical dose was given.
authors.affiliation: Radiation Modifier Research Team, Heavy-Ion Radiobiology Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan. matsumok@nirs.go.jp
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Aya
authors.initials: A
authors.lastname: Okajo
authors.forename: Katsura
authors.initials: K
authors.lastname: Nagata
authors.forename: William G
authors.initials: WG
authors.lastname: Degraff
authors.forename: Minako
authors.initials: M
authors.lastname: Nyui
authors.forename: Megumi
authors.initials: M
authors.lastname: Ueno
authors.forename: Ikuo
authors.initials: I
authors.lastname: Nakanishi
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ozawa
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: Murali C
authors.initials: MC
authors.lastname: Krishna
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Kazutoyo
authors.initials: K
authors.lastname: Endo
authors.forename: Kazunori
authors.initials: K
authors.lastname: Anzai