A study on the interactions between coenzyme Q 0 and superoxide anion. Could ubiquinones mimic superoxide dismutase (SOD)?
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An electrochemical study was carried out on 1,4-benzoquinone, duroquinone, coenzymes Q 0 and Q 10 in the absence and in the presence of molecular oxygen in aprotic (DMF) and protic (DMF/H2O 95:5 (v/v)) media. Water was added because the investigated reactions are deeply influenced by the presence of protons. Q 0 and Q 10 exhibited a similar electrochemical behaviour. Since Q 0 is more soluble in protic medium than the biologically more important analogue Q 10 , it was chosen as a model for a more detailed investigation. Voltammetric studies of Q 0 carried out in aprotic and protic media in the presence of oxygen showed that, besides simple O2 ·− dismutation, the Q 0 promoted dismutation of O2 ·− should also be considered. Spectroelectrochemical experiments with the same experimental conditions support the electrochemical results, showing that in the presence of superoxide and in aprotic medium semiquinone Q 0 ·− gives rise to a disproportionation equilibrium, while in the presence of water it tends to be reoxidized to the starting Q 0 by OOH·. EPR measurements are also in agreement with these results.
KeywordsRadical Anion Anodic Peak Ubiquinone Voltammetric Study Semiquinone Radical
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