Vanadyl-induced Fenton-like reaction in RNA. An ESR and spin trapping study.
Vanadyl (VO2+) complexed to RNA reacts with hydrogen peroxide in a Fenton-like manner producing hydroxyl radicals (.OH). The hydroxyl radicals can be spin trapped with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) forming the DMPO-OH spin adduct. In addition, in the presence of ethanol the formation of the hydroxyethyl radical adduct of DMPO (DMPO-ETOH) confirms the production of hydroxyl radicals by the RNA/VO2+ complex. When the reaction between the RNA/VO2+ complex and H2O2 is carried out in the presence of the spin trap 2-methyl-2-nitrosopropane (MNP), radicals produced in the reaction of .OH with RNA are trapped. Base hydrolysis of the MNP-RNA adducts (pH 12) followed by a reduction in the pH to pH 7 after hydrolysis is complete, yields an MNP adduct with a well-resolved ESR spectrum identical to the ESR spectrum obtained from analogous experiments with poly U. The ESR spectrum consists of a triplet of sextets (aN = 1.48 mT, a beta N = 0.25 mT and a beta H = 0.14 mT), indicating that the unpaired nitroxide electron interacts with the nuclei of a beta-nitrogen and beta-hydrogen. The results suggest that the .OH generated in the RNA/VO2+ reaction with H2O2 add to the C(5) carbon of uracil forming a C(6) carbon centered radical. This radical is subsequently spin trapped by MNP.
Carmichael
A J
AJ
Radiation Biochemistry Department, Armed Forces Radiobiology Research Institute, Bethesda, MD 20814-5145.
D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006861:Hydrogen Peroxide; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006878:Hydroxides / Q000378:metabolism*; D017665:Hydroxyl Radical; D009603:Nitroso Compounds; D012313:RNA / Q000378:metabolism*; D013113:Spin Labels; D014638:Vanadates / Q000378:metabolism*
D003497:Cyclic N-Oxides; D005609:Free Radicals; D006878:Hydroxides; D009603:Nitroso Compounds; D013113:Spin Labels; D017665:Hydroxyl Radical; D014638:Vanadates; D012313:RNA; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D006861:Hydrogen Peroxide; C034526:tert-nitrosobutane