Formation of Active Oxygen Species by the Reaction of Molecular Oxygen and Oxygen Base

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Molecular oxygen and hydroxide anion are the most fundamental row materials in oxygen chemistry. Inspection of redox potential of molecular oxygen and hydroxide anion suggest that these two species may react in aprotic solvent, in which naked hydroxide anion act as a single electron reducing agent.When a solution of ^<18>O-fabelled cesium hydroxide in hexamethylphosphoric triamide was incubated with oxygen gas in sealed tube, incorporation of ^<18>O into molecular oxygen took place even at room temperature. Since oxide anion radical were known to mediate oxygen scrambling between hydroxide anion and molecular oxygen, the our observation has been rationalyzed as follows. The single elctron transfer from hydroxide anion to molecular oxygen forming superoxide anion radical(O_<2->)and oxide anion radical(O^-)which is the conjugate base of hydroxyl radical(HO). Then the ^<18>O-D1labelled oxide anion radical reacts with unlabelled molecular oxygen to form ozone anion radical(O_<3->)which collapsed to afford unlabelled oxide anion radical and ^<18>O-labelled molecular oxygen.We found that hydroperoxyl radical, the conjugate acid of superoxide anion radical, Initiates autoxidation of dihydronfootinamide adenine dinucleotide phosphate(NADPH). We have established the method measuring steady state concentration of superoxide anion radical based on the rate of hydroperoxyl radical dependent autoxidation of NADPH. The method was applied successfully to determine steady state concentration of superoxide anlon radical in some biochemical processes.