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Updated: Jun 24, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Detection of free radical reactions in an aqueous sample induced by low linear-energy-transfer irradiation
Ken-Ichiro Matsumoto1, Aya Okajo, Katsura Nagata
1Radiation Modifier Research Team, Heavy-Ion Radiobiology Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan. matsumok@nirs.go.jp
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.
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