title: Characterization of hydantoin products from one-electron oxidation of 8-oxo-7,8-dihydroguanosine in a nucleoside model.
abstract: Use of one-electron oxidants such as Na(2)IrCl(6) to oxidize 8-oxo-7,8-dihydro-2'-deoxyguanosine (OG) residues in oligodeoxynucleotides was previously shown to lead to predominant formation of a base lesion of mass M - 10 compared to starting material [Duarte et al. (1999) Nucleic Acids Res. 27, 596-502]. To thoroughly characterize the structure of this lesion, the oxidation of the nucleoside 9-N-(2',3',5'-tri-O-acetyl-beta-D-erythro-pentanosyl)-8-oxo-7,8-dihydroguanine with one-electron oxidants at pH 2-4 was used as a model for duplex DNA oxidation of OG residues. (1)H NMR and H,H COSY NMR studies in CD(3)OD along with LC-ESI-MS/MS fragmentation analysis are consistent with the assignment of the M - 10 species as a mixture of two pH-dependent equilibrating isomers, a guanidinohydantoin (Gh) and an iminoallantoin (Ia) nucleoside, both present as mixtures of epimers at the C5 position of the hydantoin ring, i.e., four total isomers are formed. The Gh/Ia mixture is formed from hydration and decarboxylation of the initially formed intermediate 5-hydroxy-8-oxo-7,8-dihydroguanosine, a species that is also produced by four-electron oxidation (e.g., singlet oxygen) of guanosine. The product mixture can be further oxidized to a species designated Ia(ox), a hydrolytically unstable material at pH 7 that has been characterized by ESI-MS and (1)H NMR. Competition studies with 8-oxo-7,8-dihydroadenosine placed the redox potential of Gh/Ia at about 1.0 V vs NHE. These studies provide important information concerning the structures of lesions obtained when OG, a "hot spot" for oxidative damage, serves as a "hole trap" in long-range electron-transfer studies.
authors.affiliation: Contribution from the Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA.
authors.forename: W
authors.initials: W
authors.lastname: Luo
authors.forename: J G
authors.initials: JG
authors.lastname: Muller
authors.forename: E M
authors.initials: EM
authors.lastname: Rachlin
authors.forename: C J
authors.initials: CJ
authors.lastname: Burrows
mesh_terms: D000481:Allantoin / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D006146:Guanidines / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D006151:Guanosine / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry; D006827:Hydantoins / Q000032:analysis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D007553:Isotope Labeling; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010084:Oxidation-Reduction
chemical_list: D006146:Guanidines; D006827:Hydantoins; C417602:guanidinohydantion; D006151:Guanosine; D000481:Allantoin; C046215:8-hydroxyguanosine; D004247:DNA