HO effects of media and pH

Biological systems activate ground-state dioxygen (302) for controlled energy transduction and chemical syntheses via electron-transfer and hydrogen-atom-transfer reduction to O2 -, HOO-, and HOOH. These reduction products are further activated with metalloproteins to accomplish oxygen atom-transfer chemistry. Conversely, green plants via photosystem II facilitate the oxidation of water to 02 (Chapter I),l 

The reaction thermodynamics for these processes are influenced by the solution matrix and its acidity. Thus, the redox thermodynamics of O2 are directly dependent upon proton activity. 

Another limiting factor with respect to chemical-energy flux for oxidative metabolism and respiration is the solubility of O2. Because of nonpoplar 

acetonitrile DMF, dimethylformamide Me2SO, dimethyl sulfoxide py, pyridine. 

Such a proton-driven disproportionation process means that O2- can deprotonate acids much weaker than water (up to pKa 23).1  

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