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Abstract
The oxidation of Fe2+ was investigated by electron paramagnetic resonance (EPR) spin trapping techniques with N-t-butyl-α-phenylnitrone (PBN) and dimethyl sulfoxide. Under pure oxygen, the spin adduct PBN/.OCH3 was rapidly generated by the addition of Fe2+ (0.2–1.2 mM) into phosphate buffer containing ethylenediaminetetraacetate (EDTA), dimethyl sulfoxide and PBN at pH 7.4, but it decayed. The decay process of PBN/•OCH3 consists of two components. The fast decay was dependent on Fe2+ concentration. Another was due to destruction of the spin adduct by superoxide anion (•O2-), because superoxide dismutase (SOD) markedly prevented the decay. Catalase decreased the yield of PBN/•OCH3. When Fe3+-EDTA and ascorbate were used instead of Fe2+-EDTA, similar phenomena were detected. These results demonstrate that Fe2+ reacts with O2 to generate •O2-, then H2O2, which produces •CH3 by the reaction with Fe2+ and dimethyl sulfoxide. The •OCH3 radical results from the reaction between •CH3 and O2. The adduct PBN/•OCH3 decays by the reaction with Fe2+ and •O2-.