乙酰胆碱酯酶和香豆素460生物缀合物的传感性与分子对接

【作者】 蒋娟娟；

【导师】 张耀东；

【作者基本信息】 陕西师范大学 ， 分析化学， 2010， 硕士

【摘要】 两个或两个以上具有生物活性的分子连接起来形成一个新的复杂的生物缀合物。生物缀合物具有各个组成分子的性能。生物缀合物技术几乎影响到生命科学的各个领域,应用交联反应构建新颖独特的缀合物系统使得灵敏测定生物体内的目标分子及生物过程的分子调节成为可能。生物缀合物也能够作为探针探测特定细胞组分的定位,并用于疾病的治疗。分子对接是研究配体与受体之间相互作用及虚拟筛选的有效工具,在药物合理设计中起着非常重要的作用。进行分子对接时,先将受体表面特征化,寻找受体的活性位点,然后把底物放入受体的活性口袋中,通过几何匹配搜索构象,然后根据打分函数评价匹配是否合适。本论文对乙酰胆碱酯酶(AChE)和香豆素460形成的生物缀合物进行了研究,并研究应用该生物缀合物荧光法检测有机磷。利用分子对接法模拟乙酰胆碱酯酶与其配体的结合,在理论上探讨AChE与其配体的相互作用机制。本论文由三章组成：第一章为绪论,介绍了有机磷的危害和现状及检测有机磷残留方法的研究进展。在此基础上确定了本论文的选题思路和研究内容。第二章为实验部分。在pH=7.5的磷酸缓冲溶液中,AChE和香豆素460以静电作用形成生物缀合物。对氧磷可使生物缀合物的荧光强度增强。根据荧光强度变化值,计算了香豆素460在AChE上的结合位置到发光基团色氨酸残基的距离,同时也计算了AChE与香豆素460的结合常数及香豆素460-AChE生物缀合物与对氧磷的结合常数。香豆素460在AChE上的结合位置距色氨酸残基距离r=2.61nm(<7nm),试验结果也表明AChE与香豆素460间可发生荧光共振能量转移。AChE与香豆素460的结合常数ka=7.936×103,香豆素460-AChE生物缀合物与对氧磷的结合常数ka=5.12×106。利用该生物缀合物对对氧磷进行检测的线性响应范围为0.3μg·L-1-20μg·L-1,检出限为0.09μg·L-1,从而建立了测定对氧磷的方法。第三章为分子对接研究。用分子对接软件GOLD研究了AChE与香豆素460,及其与对氧磷分子的相互作用。结合模型显示,香豆素460与AChE的外周阴离子位点Trp84产生π-π堆积,质子化氮原子与Ser124形成氢键；而对氧磷与AChE疏水位点Phe330产生阳离子-π作用,氧原子与Tyr130和Gly117形成氢键,得分分别为46.50和53.83。本论文的研究为AChE与其抑制剂的相互作用模式建立了一种理论和实验研究模型,可用于筛选用于治疗的AChE抑制剂,并研究其作用方式。更多还原

【Abstract】 Bioconjugation involves the linking of two or more molecules to form a novel complex having the combined properties of its individual components. The technology of bioconjugation has affected nearly every discipline in the life sciences. The application of the available crosslinking reactions and reagent systems for creating novel conjugates with peculiar activities has made possible the assay of minute quantities of sub-stances, the in vivo targeting of molecules, and the modulation of specific biological processes.Molecular docking is to study the interaction between the ligand and the receptor and plays a important role in rational drug design. Its basic idea is to firstly feature receptor surface and find the receptor active site, then pocket the receptor into the activity of the substrate, searching conformational by geometric matching, and then evaluat of the appropriateness of matching by scoring function.Bioconjugate formed by acetylcholinesterase (AChE) and coumarin 460 was studied in this paper, and the method of detection of organophosphates was applied by using this bioconjugate; The molecular docking method was see to imitate the combining of acetylcholinesterase (AChE) and its ligand, and illustrate the interaction mechanism of acetylcholinesterase (AChE) and its ligand in theory. This thesis consises of three chapters:In chapter 1, the hazards of organophosphates was introduced and the current research activity on detection of organophosphates was reviewed. Finally, the aim of this paper was outlined.In chapter 2, AChE-coumarin 460 bioconjugate was fabricated and its characteristics were studied. In pH=7.5 phosphate buffer, AChE and coumarin 460 can form bioconjugate by electrostatic interaction.The fluorescence intensity of AChE-coumarin 460 bioconjugate was related linearly to concentration of paraoxon, thus, a method for the detection of organophosphates was established. According to the change of fluorescence intensity, the distance between Coumarin 460 and tryptophan residues of the AChE was calculated. The binding constant of AChE-coumarin 460 as well as the binding constant of paraxon with coumarin460-AChE bioconjugate were also calculated.The distance between coumarin 460 and tryptophan residues was 2.6 1nm (<7nm), proving that FRET can occur between AChE and coumarin 460. The binding constant of AChE with coumarin 460 was 7.936×103, the binding constant of coumarin 460-AChE with paraxon was 5.12×106, as the interaction between AChE and coumarin460 is electrostatic interaction, paraxon is covalently bound to AChE. Under the optimized conditions, the response of the bioconjugate fabricated was related linearly to concentration of paraxon in the range from 0.3μg·L-1-20μg·L-1, with a detection limit of 0.09μg·L-1.In chapter 3, molecular docking software GOLD was used to investigate the binding mode of coumarin 460. The conformation model indicated that phenyl ring of coumarin 460 interacts with peripheral anion sites of AChE via a classic parallelπ-πaccumulation and hydrogen bonding was formed between protonize nitrogen atom and Ser124. Paraxon interacts with the hydrophobic site Phe330 of AChE via cationic-πeffect and hydrogen bonding is simultaneously formed between oxygen atom and Tyr130 and Gly117. The fitness scores were 46.50 and 53.83, respectively.更多还原