Ultraweak luminescence (uwCL) was coupled with electron spin resonance to study the reactions of 3 heterocyclic compounds (tryptophan, serotonin and imidazole) with peroxynitrite at pH 8.7. Tryptophan and serotonin reacted with emission of a flash peak of light (5 s) followed by a long-living light emission of +/- 80 s. Addition of the spin trap 4-POBN at different intervals, after the beginning of reaction revealed that a short-living free radical was produced in the case of serotonin and imidazole, but that with tryptophan, the initial radical rearranged into a relatively long-living radical, which was still formed when 4-POBN was added after 55 s (decreasing phase of uwCL).
Copyright 1999 Academic Press.