title: Use of isotopically labelled spin-traps to determine definitively the presence or absence of non-radical addition artefacts in EPR spin-trapping systems.
abstract: EPR spin-trapping, although a powerful, sensitive technique for the study of free radicals, can be susceptible to artefacts; one of the most intractable to determine has been the non-radical addition of a substrate to a spin-trap followed by oxidation of the product to an EPR-detectable nitroxide. This work details how differentially isotopically labelled spin-traps (either nitroso or nitrone) may be used to determine the presence (or absence) of such artefacts, and provide a semi-quantitative measure of the extent of their contribution to the total EPR spectra in spin-trapping reactions. Artefactual 'ene' addition of the nitroso spin-trap 3,5-dibromo-4-nitroso-benzenesulphonic acid (DBNBS) to tryptophan followed by oxidation to EPR-detectable products has been confirmed, as has its nucleophilic addition to the thiol of glutathione to give non-EPR detectable products. The nitrone α-phenyl-N-tert-butylnitrone (PBN) exhibited no such reactivity.
authors.affiliation: a Department of Chemistry , University of York , York , UK.
authors.forename: G S
authors.initials: GS
authors.lastname: Timmins
authors.affiliation: a Department of Chemistry , University of York , York , UK.
authors.forename: G K
authors.initials: GK
authors.lastname: Barlow
authors.affiliation: a Department of Chemistry , University of York , York , UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Silvester
authors.affiliation: a Department of Chemistry , University of York , York , UK.
authors.forename: X
authors.initials: X
authors.lastname: Wei
authors.affiliation: a Department of Chemistry , University of York , York , UK.
authors.forename: A C
authors.initials: AC
authors.lastname: Whitwood