Superoxide anion radical functions

Oxidative stress involves an imbalance between cellular reactive oxygen species (ROS) and antioxidant mechanisms that keep these in check. ROS include hydrogen peroxide (H202), superoxide anion radical (02- ), and the hydroxyl radical ( OH). 02 and OH are free radicals, that is, they possess an unpaired electron. As such, free radicals are extremely reactive and will seek an electron from nearby electron-rich macromolecules, for example, proteins, lipids, and DNA, which can lead to disruption of cellular functions. 

McCord and Fridovich (70) proposed an enzymic function for erythrocuprein. They demonstrated that erythrocuprein is able to disproportionate monovalent superoxide anion radicals into hydrogen peroxide and oxygen. Detailed enzyme studies (146, 147) led to the pro... 

A. Mechanism. Alkyl halides undoubtedly represent the most well-tested functional group for nucleophilic reactivity. That superoxide ion reacts with alkyl haldies by an S 2 mechanism has been demonstrated. Dietz, et al., (J) y observed a relative reactivity which fell in the series n-BuBr > sec-BuBr > -BuBr > jt-BuBr for variation of alkyl group structure and in the series n -BuBr > n-BuOTs > n-BuCl for variation of leaving group. The former order is consistent with a Sj 2 reaction mechanism and the latter order suggests that superoxide anion radical is a strong nucleophile. 

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