Vanadyl‐induced Fenton‐like reaction in RNA

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Abstract
Vanadyl (VO2+) complexee 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 (a N = 1.48 mT, a N β = 0.25 mT and a H β = 0.14 mT), indicating that the unpaired nitroxide electron interacts with the nuclei of a β‐nitrogen and β‐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.