EPR spin-trapping studies of the reaction of hydroxyl and other electrophilic radicals with uridine and related compounds. Isotopic substitution to refine analyses and aid quantification†

Abstract

EPR spin-trapping experiments using MNP (2-methyl-2-nitrosopropane) have been employed to study radicals formed by reaction of HO˙ (generated from reaction of H₂O₂ with Fe²⁺) with uridine as a model nucleoside; studies with [5-²H]uridine, [5,6-²H₂]uridine and [1,3-¹⁵N₂] have allowed us to obtain a more detailed analysis of the spectra following HO˙ attack on uridine, for which EPR spectra cannot at present be unambiguously assigned. These studies provide detailed information concerning the analysis of hyperfine splittings and hence the quantification of the different amounts of the C(5)- and C(6)-hydroxyl-radical adducts formed following HO˙ attack, which are comparable to results obtained from pulse radiolysis studies. Studies have also been extended to investigate the reactions of both SO₄^˙– and Bu^tO˙ with uridine.