棉酚与人血清白蛋白相互作用及其分子模拟研究

摘 要 目的： 探讨棉酚与人血清白蛋白(HSA)的相互作用。方法: 采用荧光光谱方法研究在生理条件下,棉酚与人血清白蛋白（HSA）的相互作用,并采用分子对接软件模拟棉酚与人血清白蛋相互作用。结果:棉酚与HSA的结合常数为2.390 6×10⁵ L·mol^-1 (293K) 和3.576 8×10³ L·mol^-1（303K）, 具有一个结合位点,结合反应的主要作用力为氢键和范德华力,结合位置更接近于人血清白蛋白的酪氨酸残基,分子模拟分析也证实此结果。结论: 棉酚对人血清白蛋白的荧光猝灭机制属于静态荧光猝灭。     

荧光光谱法研究顺铂与牛血清白蛋白的键合

摘 要 目的：探讨在人体生理条件下顺铂与牛血清白蛋白(BSA)的结合作用。 方法: 采用荧光光谱法研究顺铂与BSA的作用机制;考察其结合常数、结合位点数和作用力类型;考察顺铂对BSA构象的影响。结果: 顺铂对BSA的猝灭过程是形成基态复合物的静态猝灭,顺铂与BSA结合位点数和结合常数分别为1.36×10⁴ L·moL^-1和0.991,两者以氢键和范德华力为主。同步荧光表明两者结合作用影响色氨酸残基所处的微环境。结论:顺铂能与BSA结合并改变BSA的构象。     

荧光光谱法研究肼黄与人血清白蛋白的结合性质

目的 研究肼黄与人血清白蛋白（HSA）间的结合性质。方法 采用荧光猝灭法对肼黄与人血清白蛋白间相互作用进行研究。结果 肼黄可以使HSA的内源荧光发生猝灭现象。肼黄与HSA相互作用的热力学参数计算结果为ΔG⁰<0、ΔH⁰<0、ΔS⁰>0。华法林的加入可使HSA-肼黄体系的荧光强度明显降低。结论 肼黄以形成HSA-肼黄复合物的静态猝灭机制与HSA发生相互作用。二者形成HSA-肼黄复合物的过程是自发进行的,疏水作用力和氢键在形成HSA-肼黄复合物的过程中发挥主要作用。肼黄在HSA上的结合位点是与华法林相同的siteⅠ位。     

基于表面等离子体共振技术筛选STAT3小分子抑制剂的研究

目的 基于表面等离子体共振（SPR）技术,筛选能与信号转导和转录激活因子3（STAT3）特异性结合并抑制其活性的小分子化合物。方法 使用基于SPR技术的Biacore T200生物分子互作分析系统,在最优pH富集条件下将纯化蛋白STAT3偶联到SPR系统的CM5芯片上,从50个中药单体中筛选出能够与STAT3结合且响应值较高的化合物,并对其结合特异性进行确认,然后运用生物学相关实验确证筛选所得化合物对STAT3的抑制作用,最后采用分子对接技术拟合化合物与STAT3的结合模式,明确其可能的作用位点。结果 初步筛选获得10多个高响应的候选分子,通过动力学测定发现其中仅有1个分子芹黄素显示特异性结合。Western-blot实验结果表明,芹黄素能够剂量依赖地抑制STAT3的磷酸化;双荧光素酶报告基因结果显示,芹黄素能够剂量依赖地抑制IL-6诱导的STAT3的转录活性。分子对接结果表明,芹黄素与STAT3蛋白的SH2结构域结合,与关键残基Glu638、Gln644、Gly656、Lys658形成氢键相互作用,与Tyr657残基形成π-π相互作用。结论 基于SPR技术筛选,发现芹黄素是STAT3的抑制剂。     

荧光光谱法研究卡铂与牛血清白蛋白的相互作用

目的研究卡铂与牛血清白蛋白(BSA)在人体生理条件下的相互作用。方法采用荧光光谱法研究卡铂与BSA的荧光猝灭机制、结合位点数、结合常数;利用热力学参数考察其作用力类型;采用同步荧光光谱法探讨卡铂对BSA构象的影响。结果卡铂与BSA形成1∶1的复合物引起BSA的荧光猝灭,其猝灭类型为静态猝灭。卡铂与BSA结合位点数为9.81×103 mol/L,两者以疏水作用为主。卡铂与BSA相互作用使色氨酸残基所处的微环境发生改变。结论卡铂与BSA相互作用形成复合物,并改变BSA的构象。     

药根碱药物相互作用及其机制研究

目的　研究药根碱 (Jat)与华法令 (War)、硫喷妥钠(Thi)、甲苯磺丁脲 (D86 0 )合用时对药物效应的影响及其机制。方法　①以药效学方法观察Jat与War合用对小鼠凝血时间的影响 ;②观察Jat与Thi合用对小鼠睡眠时间的影响 ;③观察Jat与甲苯磺丁脲合用时 ,对小鼠血糖的影响 ;④根据荧光静态猝灭理论 ,采用荧光法测定Jat与人血清白蛋白的结合常数。结果　①Jat与War合用 ,小鼠凝血时间延长 (P <0 0 1)。①Jat与Thi合用 ,能延长小鼠睡眠时间 (P<0 0 5)。③Jat与甲苯磺丁脲合用时能降低小鼠血糖水平(P <0 0 1)。④荧光法测得Jat与人血清白蛋白的结合常数为 1 2 9× 10 4 L·mol- 1,结合常数大 ,表明二者有高度的结合。结论　Jat与War、Thi、甲苯磺丁脲合用 ,可使其药效(或毒性 )增强 ,导致药物相互作用。其可能的机制是Jat竞争血浆蛋白结合部位 ,使其游离药物浓度增高 ,药效 (或毒性 )增强     

荧光光谱法研究安非他酮与人血清白蛋白的相互作用

目的 研究安非他酮与人血清白蛋白(human serum albumin,HSA)的相互作用。方法 通过荧光光谱法研究安非他酮对HSA的荧光猝灭光谱和同步荧光光谱的影响。由Stern-Volmer方程确定安非他酮对HSA的荧光猝灭机制,双对数方程确定反应结合位点和结合常数。根据热力学方程讨论两者间主要的作用力类型。结果 荧光猝灭光谱显示,安非他酮对HSA有猝灭作用,在17 ℃和37 ℃时的猝灭速率常数分别为5.714 8×10³和3.126 1×10³ L·mol^-1·s^-1,反应前后的焓变和熵变均<0,结合点数为1。结论 安非他酮对HSA的猝灭过程为静态猝灭,二者间的结合力主要为氢键和范德华力。     

钩藤碱和异钩藤碱与牛血清白蛋白的相互作用

目的 研究钩藤碱、异钩藤碱与牛血清白蛋白相互作用的荧光猝灭类型、结合位点和作用力类型。方法 采用荧光光谱法、紫外-可见分光光度法、红外光谱法以及分子对接技术进行研究。结果 钩藤碱与异钩藤碱的加入会导致牛血清白蛋白发生静态荧光猝灭,与其site I位点结合,结合位点数为1;二者与牛血清白蛋白主要以氢键和范德华力结合,可使牛血清白蛋白的二级结构发生改变。结论 阐明了钩藤碱和异钩藤碱与牛血清白蛋白相互作用的机制,为临床应用提供了实验数据。     

染料木素与β-葡萄糖苷酶相互作用的研究

本文研究了染料木素与β-葡萄糖苷酶的相互作用。采用荧光光谱法研究了染料木素与β-葡萄糖苷酶的结合反应,二者的相互作用使β-葡萄糖苷酶发生内源荧光猝灭,属于静态猝灭机制。通过计算得到染料木素与β-葡萄糖苷酶在17、27和37℃下的结合常数分别为3.69×104、3.06×104和2.36×104 L·mol-1。同步荧光研究了染料木素对β-葡萄糖苷酶结构的影响,染料木素可使β-葡萄糖苷酶的构象发生变化、色氨酸残基所处微环境的疏水性降低。染料木素对酶活性的抑制试验结果表明其对酶的活性具有明显的抑制作用,双分子结合速率常数为1.2×103(mol·L-1)-1.min-1。结合AutoDock 4.2分子对接软件模拟研究了二者的键合模式和键合机制,表明氢键和疏水作用对染料木素与β-葡萄糖苷酶的结合起重要作用,同时还存在静电作用。     

氧氟沙星与牛血清白蛋白相互作用机制

目的　以光谱技术与微量热技术相结合的方法研究水溶液中牛血清白蛋白与氧氟沙星分子间结合作用的机制。方法　用荧光猝灭法及微量热法。结果　荧光猝灭法测得该反应的结合常数K=1.20×105 L.mol^-1,结合位点数n=1.20,微量热法测得反应的焓变Δ_rH_m≈0;用同步荧光技术考察氧氟沙星对牛血清白蛋白构象的影响;依据Fōrster非辐射能量转移机制,得到授体-受体间的结合距离(r=2.59 nm)和能量转移效率(E=0.38)。结论　牛血清白蛋白与氧氟沙星分子间有较强的结合作用,且结合力以疏水作用为主。     

光谱法和分子对接法研究盐酸雷尼替丁与溶菌酶的相互作用

目的 用荧光光谱法、紫外光谱法和分子对接研究生理条件下盐酸雷尼替丁与溶菌酶相互作用的光谱特性,为盐酸雷尼替丁的体内代谢过程提供一定的理论依据.方法 在激发波长(λex)282 nm条件下,测定盐酸雷尼替丁与溶菌酶在不同温度下的荧光猝灭光谱;使用Stern-Volmer曲线方程判断猝灭机制;计算其结合常数(K)、结合位点...     

牡荆苷与溶菌酶相互作用的荧光光谱学研究

目的在模拟人体生理条件下,研究牡荆苷与溶菌酶的相互作用的光谱学特征。方法利用同步荧光光谱法和荧光光谱法研究牡荆苷与溶菌酶的相互作用机制、作用力类型,考察牡荆苷对溶菌酶构象的影响。结果牡荆苷对溶菌酶的荧光猝灭机制为静态猝灭,牡荆苷与溶菌酶的结合常数、结合位点数分别为6.73×10~5 L/mol、1.12,其作用力以疏水作用为主。同步荧光光谱法测定的结合位点靠近色氨酸,并使色氨酸的疏水性增强。结论牡荆苷与溶菌酶结合并改变溶菌酶的构象,共存金属离子对牡荆苷与溶菌酶的相互作用有一定的影响。     

The interaction of bovine serum albumin with doxorubicin-loaded superparamagnetic iron oxide nanoparticles: spectroscope and molecular modelling identification

Abstract

To take a comprehensive evaluation of the bio-safety of doxorubicin-loaded superparamagnetic iron oxide nanoparticles (SPION), the interaction of bovine serum albumin (BSA) with the drug delivery was investigated by multi-spectroscopic techniques and molecular modelling calculation. Ultraviolet absorption and synchronous fluorescence results elucidate that DOX-SPION unfold the framework conformation of BSA, leading to changes in the microenvironment of amide moieties. Circular dichroism (CD) data show that the content of α-helix decreases from 68.62% to 62.76%, which shows the changes of protein's secondary structure quantificationally. Through Stern–Volmer analysis, the quenching mode is determined to be static interaction, forming a stable bioconjugate. The molecular model illustrates that DOX prefers a highly polar binding site at the external region of domains □ of BSA, and the hydrogen bonds are marked. This work elucidates that the drug delivery has deleterious effects on the frame conformation of protein, affecting its physiological function.     

Pharmacophore, QSAR, and binding mode studies of substrates of human cytochrome P450 2D6 (CYP2D6) using molecular docking and virtual mutations and an application to chinese herbal medicine screening

The highly polymorphic human cytochrome P450 2D6 (CYP2D6) metabolizes about 25% of currently used drugs. In this study, we have explored the interaction of a large number of substrates (n = 120) with wild-type and mutated CYP2D6 by molecular docking using the CDOCKER module. Before we conducted the molecular docking and virtual mutations, the pharmacophore and QSAR models of CYP2D6 substrates were developed and validated. Finally, we explored the interaction of a traditional Chinese herbal formula, Fangjifuling decoction, with CYP2D6 by virtual screening. The optimized pharmacophore model derived from 20 substrates of CYP2D6 contained two hydrophobic features and one hydrogen bond acceptor feature, giving a relevance ratio of 76% when a validation set of substrates were tested. However, our QSAR models gave poor prediction of the binding affinity of substrates. Our docking study demonstrated that 117 out of 120 substrates could be docked into the active site of CYP2D6. Forty one out of 117 substrates (35.04%) formed hydrogen bonds with various active site residues of CYP2D6 and 53 (45.30%) substrates formed a strong π-π interaction with Phe120 (53/54), with only carvedilol showing π-π interaction with Phe483. The active site residues involving hydrogen bond formation with substrates included Leu213, Lys214, Glu216, Ser217, Gln244, Asp301, Ser304, Ala305, Phe483, and Phe484. Furthermore, the CDOCKER algorithm was further applied to study the impact of mutations of 28 active site residues (mostly non-conserved) of CYP2D6 on substrate binding modes using five probe substrates including bufuralol, debrisoquine, dextromethorphan, sparteine, and tramadol. All mutations of the residues examined altered the hydrogen bond formation and/or aromatic interactions, depending on the probe used in molecular docking. Apparent changes of the binding modes have been observed with the Glu216Asp and Asp301Glu mutants. Overall, 60 compounds out of 130 from Fangjifuling decoction matched our pharmacophore model for CYP2D6 substrates. Fifty four out of these 60 compounds could be docked into the active site of CYP2D6 and 24 of 54 compounds formed hydrogen bonds with Glu216, Asp301, Ser304, and Ala305 in CYP2D6. These results have provided further insights into the factors that determining the binding modes of substrates to CYP2D6. Screening of high-affinity ligands for CYP2D6 from herbal formula using computational models is a useful approach to identify potential herb-drug interactions.     

光谱法研究野漆树苷与人血清蛋白的结合作用

目的研究野漆树苷与人血清蛋白(HSA)的结合作用及机制。方法通过光谱法研究野漆树苷与HSA的作用机制。以能量传递原理及Lineweaver-Burk双倒数方程计算野漆树苷与HSA反应的结合常数和结合距离;以热力学参数判断其与HSA间的作用力类型;以同步荧光光谱考察野漆树苷对HSA构象的影响。结果野漆树苷与HSA反应的结合常数随温度的升高而降低;野漆树苷与HSA之间的结合距离为4.16 nm;野漆树苷与HSA的互相作用以氢键和范德华力结合为主;酪氨酸残基和色氨酸残基的特征荧光光谱峰随野漆树苷浓度的增加而产生猝灭。结论野漆树苷能与HSA结合,其荧光猝灭以静态猝灭为主。     

Characterization of thymoquinone binding to human α₁-acid glycoprotein

Thymoquinone (TQ) is the main bioactive component isolated from Nigella sativa essential oil and seeds and has been used for the treatment of inflammations, liver disorders, arthritis, and is of great importance as a promising therapeutic drug for different diseases including cancer. This paper reports the first experimental evidence on binding of TQ to human α(1)-acid glycoprotein (AGP), an important drug-binding glycoprotein in human plasma, which affects pharmacokinetic properties of various therapeutic agents. The interaction of TQ with AGP has been characterized by Fourier transform infrared (FTIR) and fluorescence spectroscopy, as well as by molecular docking experiments. FTIR spectroscopy showed that the binding of TQ to AGP slightly increases its thermal stability and shifts the existence of a molten globule-like state observed in a previous study to higher temperature. The binding constants K(a); the number of binding sites n; and the corresponding thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures were calculated through fluorescence spectroscopy. Fluorescence quenching experiments indicated that TQ binding involves hydrophobic interactions and to a lower extent hydrogen bonds, in agreement with molecular docking experiments. The data on binding ability of TQ to AGP represent basic information for the TQ pharmacokinetics such as drug metabolism and distribution in the body.     

Binding interactions of niclosamide with serum proteins

A study of the binding of niclosamide (NC) to serum proteins such as human serum albumin, hemoglobin, and globulin was carried out using fluorescence and UV-visible spectroscopy. Interactions between NC and these proteins were estimated by Stern–Volmer and van't Hoff equations. The binding constants and the thermodynamic parameters, ΔH, ΔS, and ΔG at different temperatures were also determined by using these equations. Data showed that NC may exhibit a static quenching mechanism with all proteins. The thermodynamic parameters were calculated. Data showed that van der Waals interactions and hydrogen bonds are the main forces for human serum albumin and hemoglobin. Globulin, however, bound to NC via hydrophobic interaction. The spectral changes of synchronous fluorescence suggested that both the microenvironment of NC and the conformation of the proteins changed in relation to their concentrations during NC's binding.     

Probing the molecular mechanism of C.I. Acid red 73 binding to human serum albumin

The molecular mechanism of C.I. Acid red 73 binding to human serum albumin (HSA) was investigated by spectroscopy and molecular docking procedures. The molecular docking results indicated that subdomain IB of HSA was the main active binding site for C.I. Acid red 73. The spectroscopic experiment results showed that the mechanism of the interaction between C.I. Acid red 73 and HSA was dominantly initiated by complex formation and the number of binding site (n) was 1.71 at 298K. The molecular docking study and thermodynamic analysis suggested that the forces acting was predominantly hydrophobic and hydrogen bond interactions. Far-UV circular dichroism (CD) spectroscopy also revealed that the conformation of the HSA changed slightly after C.I. Acid red 73 bound to the HSA. The mean distance between the bound dye and the Trp residue is 3.28nm as calculated from F?rster energy transfer.     

木犀草素与牛血清白蛋白相互作用的荧光光谱法研究

本文首次采用荧光光谱法研究传统中药白毛夏枯草中活性成分木犀草素与牛血清白蛋白（BSA）的猝灭机制。实验研究了木犀草素在291 k和310 k条件下与BSA的猝灭情况,通过计算求得不同温度下的热力学参数。结果表明木犀草素对牛血清白蛋白荧光的猝灭机制属于静态猝灭过程,二者之间的作用力主要为范德华力和氢键。此外,实验还考察了木犀草素对BSA构象的影响。