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

分子氧和氢氧阴离子是氧化学中最基本的两种物质。对分子氧和氢氧阴离子的氧化还原电势的考察表明，这两种物种可能在非质子溶剂中反应，在非质子溶剂中，氢氧阴离子充当单电子还原剂。当六甲基磷三酰胺中的氢氧化铯溶液与氧气在密封管中孵化时，即使在室温下，也能将^&lt；18&gt；O加到分子氧中。由于氧阴离子自由基介导氢氧阴离子和分子氧之间的氧争夺，我们的观察结果被合理地分析如下。单电子从氢氧阴离子转移到分子氧上，形成超氧阴离子自由基(O&lt；2-&gt；)和氧阴离子自由基(O^-)，氧阴离子自由基是羟基自由基(HO)的共轭碱基。然后，~&lt；18&gt；O-D1标记的氧阴离子自由基与未标记的分子氧反应生成臭氧阴离子自由基(O_&lt；3-&gt；)，臭氧阴离子自由基坍塌生成未标记的氧阴离子自由基和~&lt；18&gt；O标记的分子氧自由基。建立了基于过氧化氢自由基依赖的NADPH自氧化速率来测定超氧阴离子自由基稳态浓度的方法。该方法已成功应用于某些生化过程中超氧阴离子自由基的稳态浓度测定。

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.