| This paper includes five parts as follows.Part 1 Since McCord and Fridovich discovered superoxide dismutase (SOD) and investigated its biological activities in 1968, the raised doctrine for oxygen toxicity about superoxide anion free radical has popularly attached much importance to the studies on superoxide anion. Superoxide anion O2.- can be induced by electron transfer reaction in vivo to generate other active oxygen species such as hydroxyl free radical and hydrogen peroxide, which are nearly responsible for many biofunctions and diseases of cell. It is very clear that superoxide anion is related to senescence, tumor, inflammation, metabolism of drugs, etc. Therefore, many researches for bioactive compounds either to scavenge O2.- or to inhibit O2.- generation are of particular interest. Currently, the scavenging mechanism for O2.- and kinetics or dynamics studies on its production and disproportionation has been going ahead, which is of importance for understanding the exterior or interior regulation process for organism and guarding against, and remedying the damage and diseases, of cell, induced by active oxygen species. In this part, progress in the generation, detection, chemical property, reaction kinetics, biology and application of superoxide anion O2.- was summarized.Part 2 In 0.1 mol/L NaHCO3 medium, the chemical reaction of progesterone with superoxide anion O2.- is studied by polarography. Differing from the indirect inhibition of O2.- generation by synthesized glucocorticoids in mechanism, the function that progesterone scavenges O2.- ascribes to that O2.- directly oxidizes the C=C double bond conjugated with the carbonyl moiety of progesterone molecule to a free radical, and then is reduced to H2O2. The result obtained in this paper gives new evidence for biomedical research. The equation of rate constant of the oxidization reaction is deduced, and the apparent rate constant obtained is 308.L.mol-1.s-1.Part 3 In 0.1 mol/L NaHCO3 medium, the chemical reaction of hydrocortisone with superoxide anion O2.- is studied by voltammetry. Experimental results prove that hydrocortisone, as a scavenger of O2.-, catalyze the dismutation reaction of O2.-. The reaction progression of the catalytic dismutation is zero for O2.-, but two for hydrocortisone. The equation of rate constant for the catalytic dismutation reaction is deduced, and the apparent rate constant obtained is 8.76×105L.mol-1.s-1.The result obtained gives new evidence for biomedical research. Besides the indirect inhibition of O2.- generation by such synthesized glucocorticoids as hydrocortisone suppressing the activity of phospholipase A2, chemically hydrocortisone can also directly scavenge O2.- produced. Therefore, the activity of hydrocortisone as anti-inflammatory drug is ascribed to the combination of its biologic effectiveness and chemical scavenging for O2.-.Part 4 Polarographic responses of the dissolved oxygen in phosphate (pH7.4)-anion surfactant sodium dodecyl sulfate (SDS) medium were investigated by cyclic voltammetry and normal pulse voltammetry. The obtained results indicate that when the SDS concentration is up to 1.0×10-4mol/L there are three reduction waves corresponding to the following electrode processes of oxygen species: O2 + e → O2.-, O2.- + 2HA + e → H2O2 + 2A- and H2O2 + 2HA + 2e →2H2O + 2A- (where HA presents proton donor), which is different from that in aqueous solution containing such surfactants as triphenylphosphine oxide or quinoline. This new medium system is available for studying the chemical reaction and kinetics of scavenging O2.- by low molecular weight organic compounds and drugs, and was used to investigate the dismutation of O2.- catalyzed by tyrosine. The reaction rate constant of O2.- with tyrosine determined, 2.69×104 L.mol-1.s-1, is in agreement with that obtained by quenching chemiluminescence. The model of electric field concerned with the anion surfactant on electrode surface was proposed. It is suggested that an additional contribution to the...
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