OXYGEN-EXCHANGE REACTIONS ACCOMPANYING OXIDATION OF VANADYL SULFATE BY DIPEROXOVANADATE

The absorption spectrum in the visible range and the, ESR spectrum of vanadyl sulfate were lost on addition of diperoxovanadate. The V-51-NM R spectra revealed that diperoxovanadate was reduced to vanadate and i ts oligomers. With excess vanadyl, tetrameric vanadate was found to be the major product, During this reaction oxygen was released into the medium. The oxygen-release reaction was inhibited by a variety of orga nic ligands-imidazole, benzoate, formate, mannitol, ethanol, Tris, DMP O, malate, and asparagine. An oxygen-consuming reaction emerged at hig h concentrations of some of these compounds, e.g. benzoate and ethanol . Using DMPO as the spin-trap, an oxygen-radical species with a 1:2:2: 1 type of ESR spectrum was detected in the reaction mixtures resulting from vanadyl oxidation by diperoxovanadate which was unaffected by ad dition of catalase or ethanol. The results showed that secondary oxyge n-exchange reactions occur which depend on and utilize the intermediat es in the primary reaction during diperoxovanadate-dependent oxidation of vanadyl sulfate.