Peroxynitrite reacts with biological nitrogen-containing cyclic molecules by a radical pathway, as demonstrated by ultraweak luminescence coupled with ESR technique

Ultraweak luminescence (uwCL) was coupled with electron spin resonance to s tudy the reactions of 3 heterocyclic compounds (tryptophan, serotonin and i midazole) with peroxynitrite at pH 8.7. Tryptophan and serotonin reacted wi th 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 interva ls, after the beginning of reaction revealed that a short-living free radic al was produced in the case of serotonin and imidazole, but that with trypt ophan, the initial radical rearranged into a relalively long-living radical , which was still formed when 4-POBN was added after 55 s (decreasing phase of uwCL). (C) 1999 Academic Press.