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Updated: Aug 15, 2026

Detection of Nitric Oxide and Superoxide Radical Anion by Electron Paramagnetic Resonance Spectroscopy from Cells using Spin Traps
Published on: August 18, 2012
The diffusion-controlled reaction of semioxidized tryptophan with the superoxide radical anion
R Santus1, L K Patterson, M Bazin
1Laboratoire de Physico-Chimie de l'Adaptation Biologique, INSERM U 312, Muséum National d'Histoire Naturelle, Paris, France.
Abstract:
From pulse radiolysis measurements in oxygenated aqueous solution, the semioxidized tryptophan radical (Trp.- formed by the one-electron oxidation of Trp by Br2- radical--has been shown to oxidize the superoxide radical anion with a rate constant of k = 2 x 10(9) M-1 s-1. Proof of this reaction is found in addition of superoxide dismutase (SOD) to the system, which totally eliminates the contribution of the Trp. + O2- mechanism to Trp. decay. Little, if any, reaction of molecular oxygen with Trp. may be observed on the time scale of the pulse radiolysis experiment.
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