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The ESR spectrum of SO3- is observed directly during the oxidation of (bi)sulfite to sulfate by horseradish peroxidase. This radical exhibits a single line at g = 2.0031. The SO3-radical can be trapped with nitrosobenzene, yielding an ESR spectrum with coupling constants AN = 12.3 G,AHp = AHo = 2.4 G, and AHm = 0.9 G, and a g-value of 2.0053. SO3- is an(More)
The one-electron oxidation of (bi)sulfite is catalyzed by peroxidases to yield the sulfur trioxide radical anion (SO3-), a predominantly sulfur-centered radical as shown by studies with 33S-labeled (bi)sulfite. This radical reacts with molecular oxygen to form a peroxyl radical. The subsequent reaction of this peroxyl radical with (bi)sulfite has been(More)
The (bi)sulfite ion undergoes extensive autoxidation in neutral aqueous media with the formation of sulfur trioxide radical anion that is detected by ESR. The radical anion subsequently reacts with molecular oxygen to form a peroxyl radical. We find that when (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) is included in this autoxidation(More)
The mechanism of prostaglandin synthase-dependent (bi)sulfite (hydrated sulfur dioxide) oxidation was investigated using an enzyme preparation derived from ram seminal vesicles. The horseradish peroxidase-catalyzed oxidation of (bi)sulfite was used as a model system. Incubation of (bi)sulfite with prostaglandin synthase and arachidonic acid,(More)
Nifurtimox is reduced by rat liver microsomes to a nitro anion-free radical as indicated by ESR spectroscopy. This subcellular fraction gives a steady state radical concentration which is proportional to the square root of the protein concentration, suggesting that the nifurtimox anion radical is a necessary intermediate in the reduction and that the(More)
The oxidation of L-cysteine by horseradish peroxidase in the presence of oxygen forms a thiyl free radical as demonstrated with the spin-trapping ESR technique. Reactions of this thiyl free radical result in oxygen consumption, which is inhibited by the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide. Cysteine sulfinic acid, a cysteine metabolite, is a poorer(More)
Direct electron spin resonance was used to detect tert-alkylperoxyl radicals generated by hematin and the corresponding hydroperoxides at near-physiological pH values. The spin-trapping method was necessary to detect the less persistent primary ethylperoxyl radical. Under a nitrogen atmosphere, the electron spin resonance signal of the tert-alkylperoxyl(More)
A back-extraction methodology is presented which involves extraction of a spin adduct from an organic medium into an aqueous medium where its spectral parameters are well established. This technique should prove very useful in properly identifying spin adducts formed in organic media. Some of the hazards of extracting spin adducts into organic solvents for(More)
Malondialdehyde, a product of lipid peroxidation, and acetylacetone undergo one-electron oxidation by peroxidase enzymes to form free radical metabolites, which were detected with ESR using the spin-trapping technique. The structures of the radical adducts were assigned using isotope substitution. With both malondialdehyde and acetylacetone and the enzymes(More)