Superoxide Anion Radical as a Substrate

Since 05 is a conjugate base of weak acid, HO2 (p ATa=4.9), and also an anion radical at physiological pH, it can perform both ionic and radical reactions. As an anion 05 has reactivies such as nucleophilic substitution and addition reactions, and as a radical, it performs hydrogen-withdrawal reactions, one-electron reduction or oxidation reactions and the disproportionation reaction. In aqueous medium, the radical reactions are 

one 05 barely reacts with the other, and the decay of most superoxide proceeds through the interaction between HO2 and 05. In aprotic environments such as membranes, the life time of 05 is prolonged due to the unavailability of protons. 

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