作者:邵勇
院校:西北大学
关键字:
学位:硕士
专业:分析化学

摘要:
本论文的研究工作包括五个部分。 第一部分 自从1968年McCord和Fridovich发现超氧化物歧化酶(SOD)并研究了其生物学作用后，提出的氧毒性的超氧化物自由基学说引起了各界学者对超氧阴离子自由基O2.-研究的普遍重视。分子氧在一电子还原时有O2.-中间体生成。O2.-可作为电子的给予体，又可接受电子，在体内可通过电子转移反应衍生出其它活性氧，研究表明O2.-与衰老、肿瘤、炎症、外源物代谢等生物学过程密切相关。对O2.-的研究已有综述报道,目前对O2.-的清除机理、O2.-的形成和消除过程的动力学和动态学研究正在不断深入，这对了解生物体的自我调控和外力调控过程，对预防和治疗活性氧引起的细胞损伤和疾病的研究有重要意义。本文综述了超氧阴离子O2.-的产生、检测、化学性质、反应动力学、生物学研究、应用等方面的研究进展。 第二部分 在0.1mol/L NaHCO3介质中,用极谱法研究了O2.-与黄体酮(PRG)的化学反应。实验表明，与具有类似结构的糖皮质类甾体抑制磷脂酶A2的活性从而间接阻止O2.-的产生机理不同，黄体酮与O2.-自由基的化学反应机制为O2.-氧化黄体酮分子中的烯酮基, O2.-自身被还原生成H2O2,PRG是O2.-的清除剂。本结论为医学组织研究结果提供了新的实验证据。推导了化学反应速率常数公式，测得O2.-氧化黄体酮的表观化学反应速率常数为308L.mol-1.s-1。 第三部分 在 0.1mol/L NaHCO3介质中,用伏安法研究了超氧阴离子 O2.- 与糖皮质类甾体氢化可的松的化学反应。实验表明，氢化可的松清除 O2.- 的化学作用机制为氢化可的松催化 O2.- 的歧化反应, 氢化可的松是 O2.- 的清除剂。氢化可的松催化 O2.- 歧化反应的速率对 O2.- 为零级反应,对氢化可的松则为二级反应, 求得 20℃时氢化可的松催化 O2.- 歧化反应表观速率常数k为 8.76×105 L???mol-1?s-1。本结论为医学组织研究结果提供了新的实验证据。在抗炎作用方面，氢化可的松除抑制磷脂酶A2 的活性从而间接阻止 O2.- 的产生外，还能直接化学清除产生的 O2.-，认为氢化可的松的抗炎作用应是这种生物的和化学的综合作用结果。 第四部分 在pH7.4的磷酸盐介质中,溶解氧于汞电极上产生两个双电子极谱还原波。有阴离子表面活性剂十二烷基硫酸钠存在（浓度大于1.0×10-4mol/L）时，则产生三个极谱还原波，其还原过程为：O2 + e → O2.-、O2.- + 2HA + e → H2O2 + 2A-、H2O2 + 2HA + 2e →2H2O + 2A-，其中HA为质子贡体。这与三苯基氧化膦（TPO）或喹啉等存在下的结果不一致。在电极表面由于有超氧阴离子O2.-稳定存在，可方便地用于研究一些有机小分子了对O2.-的清除作用的化学反应及其动力学。实验表明，酪氨酸能催化O2.-的歧化反应，测得催化歧化反应速率常数为2.69×104L.mol-1.s-1。这一结果与文献中用其它方法测定的结果一致。本文提出了这种作用的理论模型。我们认为除电极表面的疏水微环境外，表面活性剂分子在电极表面的定向排列形成的电场都有利于O2.-在电极表面的稳定产生。 第五部分 在0.125 mol/L磷酸盐 (pH 6.6)-2.5×10-4 mol/L 碘乙酰胺溶液中, 洛美沙星（lomefloxacin）能产生极谱催化波响应。其二阶导数峰电流与洛美沙星浓度在1.0×10-8～1.0×10-6 mol/L (r=0.998)范围内成线性关系。极谱催化波的灵敏度约为相应还原波的25倍（对5.0×10-7 mol/L洛美沙星而言）。拟定的方法已成功地运用于药物中洛美沙星的测定。该极谱还原波是由洛美沙星两性离子中碳-碳双键的一电子还原产生的，此过程同时伴随有酸碱平衡。在电极表面碘乙酰胺的还原产物自由基能氧化洛美沙星的一电子还原产物，从而再生洛美沙星分子，产生极谱催化波。
Abstract:
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