Nitric oxide and nitroxides can act as efficient scavengers of protein-derived free radicals

Magdalena A. Lam, David I. Pattison, Steven E. Bottle, Daniel J. Keddie, Michael J. Davies

Research output: Contribution to journalArticlepeer-review

63 Citations (Scopus)


Nitric oxide (NO) may act as either a pro-oxidant or an antioxidant in biological systems. Although NO and nitroxide radicals react slowly with most molecules, they react at near diffusion-controlled rates with other radicals and may therefore be efficient protective agents. This study assessed the ability of NO and nitroxides to intercept specific protein-derived radicals and compared the efficacy of these species. Three protein radical systems were investigated as follows: BSA-derived radicals generated via radical transfer from H 2O2-activated horseradish peroxidase, radicals formed on myoglobin via reaction with H2O2, and carbon-centered radicals formed from amino acid hydroperoxides on exposure to Fe 2+-EDTA. In each case, radicals were generated in the absence or presence of NO or nitroxides of different size and charge. Concentration-dependent loss of the protein radicals was detected by electron paramagnetic resonance with both NO and nitroxides and time-dependent consumption of NO using an NO electrode. The protein oxidation product dityrosine was significantly reduced by NO and nitroxides, and 3,4-dihydroxyphenylalanine levels were reduced by nitroxides but not NO. Overall, these studies demonstrate that NO and nitroxides are efficient near-stoichiometric scavengers of protein radicals and, hence, are potential protective agents against protein oxidation reactions and resulting damage. These reactions show little dependence on nitroxide structure or charge.

Original languageEnglish
Pages (from-to)2111-2119
Number of pages9
JournalChemical Research in Toxicology
Issue number11
Publication statusPublished - Nov 2008
Externally publishedYes


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