光谱及分子模拟法对HSA和BSA与酪氨酸激酶抑制剂Imatinib相互作用的比较分析

研究一种酪氨酸激酶抑制剂（tyrosine kinase inhibitor, TKI）伊马替尼（imatinib, IMA）与人血清清蛋白（HSA）及牛血清清蛋白（BSA）的相互作用,比较分析HSA和BSA与IMA相互作用机制的差异. 模拟生理条件下,计算机模拟技术结合荧光光谱和紫外光谱法,研究IMA与蛋白质的作用机制. 分子模建IMA与血清清蛋白的结合模型,表明伊马替尼与蛋白质的相互作用力为疏水作用力,兼有氢键作用. 光谱结果表明,IMA与HSA和BSA的相互作用表现为静态结合过程,结合强度较强,IMA与HSA和BSA分子的结合距离r值较小,说明发生了能量转移现象. IMA对HSA和BSA的结构域微区构象产生影响,使结合位域的疏水性发生改变. 荧光相图技术解析出IMA与HSA和BSA反应构象型态的变迁为“二态”模型. HSA与IMA相互作用的热力学参数表明,IMA与HSA之间是以疏水作用为主的分子间作用,而IMA与BSA之间的作用力为氢键和范德华力,兼有少量的疏水作用力. 光谱实验与计算机模拟结果基本一致,可为研究IMA与HSA和BSA相互作用本质提供一定参考.     

血清白蛋白与酪胺分子的体外相互作用分析

利用毛细管电泳 (capillary electrophoresis, CE)建立牛血清白蛋白(bovine serum albumin, BSA)-酪胺(tyramine, TA)分子作用机制的分析方法,构建TA-BSA相互作用模型,并研究其相互作用机理. 生理条件下,采用HD法(Hummel-Dreyer, HD),前沿分析法(frontal analysis, FA)和空峰法(vacant peak, VP)研究TA与BSA的结合机制,构建TA-BSA理论模型,获取TA和BSA相互作用参数,分析理论模型的适用度. 通过分子模拟,构建TA与BSA的结合模型,考察TA的BSA结合机制. 结果表明,HD法和VP法均适用于分析TA-BSA体系的相互作用,VP法最优. 模型适用度分析得出双对数方程最适合模拟TA-BSA相互作用,TA与BSA结合强度较弱,且只有单一类型的结合位点. 构建的TA与BSA结合模型表明,TA与BSA的相互作用力主要是氢键和范德华力,兼有疏水作用力. 本文结果可为分析生物胺-蛋白质分子作用机制研究提供有意义的参考.     

光谱法研究单硝酸异山梨酯与牛血清白蛋白的相互作用

为研究单硝酸异山梨酯(IM)与牛血清白蛋白(BSA)之间的相互作用,用紫外-可见光谱法和荧光光谱法在优化的实验条件下进行研究。结果表明:IM与BSA形成基态复合物从而猝灭BSA的内源性荧光,猝灭机理为静态猝灭。通过计算得出IM与BSA的结合常数Kb及结合为点数n。根据热力学参数确定了IM和BSA之间的作用力类型主要为静电引力。生成自由能变驻G为负值,表明IM与BSA的作用过程是一个自发过程。同步荧光光谱表明IM对BSA构象产生很微弱的影响,使BSA腔内疏水环境的极性减弱。同步荧光光谱显示两者的结合位点更接近于酪氨酸,两者的结合部位主要位于亚螺旋域ⅢA中。Hill系数nH1,表明IM有正协同作用。为后续硝酸脂类药物的研发和进一步探讨IM在生物体内与蛋白质的作用机制和生物学效应提供了理论依据。     

荷叶中紫云英苷和牛血清白蛋白相互作用的光谱学研究

本文采用荧光光谱法、紫外光谱法研究在生理条件(pH=7.4)下荷叶中紫云英苷(AST)与牛血清白蛋白(BSA)的相互作用。结果表明AST可与BSA结合并通过静态猝灭作用机制对BSA内源性荧光进行猝灭。在温度为298K及308K时,测得其猝灭速率常数(Kq)分别为4.31×1013L/mol/s和3.72×1013L/mol/s;结合常数(Kd)分别为2.009×105L/mol和0.927×105L/mol;结合位点数(n)分别为0.943和0.893。依据298K时测定的反应自由能变(△G0=-30.25kJ/mol),反应焓变(△H0=-59.02kJ/mol)及反应熵变(△S0=-96.54J/mol/K),结果发现AST与BSA间的结合反应可自发进行且其作用力主要表现为氢键和范德华力。此外,根据Frster非辐射能量转移理论得到AST与BSA之间的结合距离(r)为4.13nm,表明非辐射能量可从BSA转移至AST。     

诺氟沙星与牛血清白蛋白相互作用的研究

用荧光光谱法研究诺氟沙星与牛血清白蛋白之间的结合作用,确定了诺氟沙星与牛血清白蛋白的荧光猝灭机制为静态猝灭。通过测定和计算不同温度下该结合反应的结合常数和结合位点数,并根据热力学方程求得了结合反应的热力学参数,讨论了两者问的主要作用力类型是范德华力和氢键。同时采用同步荧光技术考察了诺氟沙星对BSA构象的影响。并从荧光寿命进一步证明诺氟沙星与牛血清白蛋白的荧光猝灭机制为静态猝灭。     

胡椒碱分子键合人血清白蛋白位点的表征

利用荧光光谱法、紫外光谱法并结合计算机模拟技术在分子水平上研究了胡椒碱与人血清白蛋白(human serum albumin HSA)的键合作用.同步荧光及紫外光谱图表明,胡椒碱对HSA微环境有影响.位点竞争试验证明,胡椒碱分子键合在HSA的位点Ⅱ区.通过荧光光谱滴定数据求得不同温度下(300K 310K和318 K)药物与蛋白相互作用的结合常数及结合位点数.分子模拟的结果显示了胡椒碱与HSA的键合区域和键合模式,表明药物与蛋白有较强的键合作用;维持药物与蛋白质的相互作用力主要是疏水用,兼有氢键(位于氨基酸残基Arg 257,Arg 222及Arg218位).通过实验数据计算得到的热力学参数(ΔH0与ΔS0的值分别为原33.11 kJ·mol-1和原18.90 J·mol原1·K-1)确定了胡椒碱与HSA分子的相互作用力类型主要为氢键兼范德华力.     

光谱法和分子对接研究二氢杨梅素与人血清白蛋白相互作用

运用光谱法和分子对接理论研究了二氢杨梅素(dihydromyricetin,DMY)与人血清白蛋白(Human serum albumin,HSA)的相互作用。结果表明,DMY有规律的使HSA内源荧光猝灭,其猝灭机制为两者形成复合物而引起的的静态猝灭;两者结合常数KA均大于105L/mol,结合位点数n接近于1。根据热力学参数判断,两者结合反应能自发进行,主要作用力类型为静电作用力。计算得到DMY与HSA的结合距离r为3.32 nm,表明两者结合过程发生了非辐射能量转移。同步荧光和三维光谱分析结果显示,DMY使HSA的构象发生了一定程度的改变。位点竞争实验和分子对接结果表明,DMY在HSA上的更倾向结合位于亚结构域IIA(Site I)。     

荧光光谱法研究淫羊藿苷和淫羊藿次苷Ⅰ与牛血清白蛋白的相互作用

在模拟生理条件下应用荧光光谱学方法分别研究了淫羊藿苷和淫羊藿次苷Ⅰ与牛血清白蛋白（BSA）间的结合作用. 根据荧光强度数据,计算出了结合常数KA,结合位点数n和热力学参数（△G, △H 和△S）. 实验结果表明,淫羊藿苷和淫羊藿次苷Ⅰ都能显著猝灭BSA的内源荧光,猝灭机制均为形成基态复合物的单一静态猝灭过程. 不同温度下（17 ℃, 27 ℃, 37 ℃）得到的KA和n值,表明淫羊藿次苷Ⅰ与BSA的结合强于淫羊藿苷. 从得到的热力学参数判断,淫羊藿苷与BSA间的主要作用力是氢键作用和范德华力,而疏水作用和静电引力在淫羊藿次苷Ⅰ与BSA形成复合物过程中起主导作用.而且同步荧光光谱显示,淫羊藿苷和淫羊藿次苷Ⅰ与BSA的结合导致BSA构象发生了变化.     

香草酸与多酚氧化酶相互作用机制研究及新型指纹谱构建

生物大分子与小分子之间的相互作用机制研究是当今各个学科领域的前沿和热点,不仅有利于进一步认识大分子的结构和功能,还能进一步获得检测生物大分子或小分子的新途径．本研究将中药材特征指纹图谱应用于植物多酚氧化酶(polyphenol oxidase, PPO)与植物体内活性成分香草酸(vanillic acid, VA)的具体相互作用机制的研究,采用光谱实验法结合分子模拟技术,分析VA与PPO的相互作用机制,并构建其三维相互作用指纹谱．光谱实验结果显示,VA增强了PPO的荧光强度. 维持VA-PPO体系的相互作用力主要为疏水作用,VA与PPO的结合距离r值为2.48 nm,发生了非辐射能量转移．由光谱实验数据构建的λ-UV-F新型指纹图谱,系统地反映了活性分子VA与PPO之间相互作用特征．分子模拟结果精确显示了VA与PPO的结合位域与结合作用力,表明维持VA与PPO的相互作用力主要为疏水作用和氢键(位于氨基酸残基 Met258, His88, His109, His240, His244和His274位)．计算机模拟与光谱学实验结果一致,并成功构建了VA-PPO相互作用特征关系的新型指纹图谱．     

牛胰多肽(BPP)及去氧胆酸盐(DOC)与DMPC脂质体相互作用的激光拉曼光谱研究

本文报导用激光拉曼光谱技术研究牛胰多酞(BPP)和去氧胆酸盐(DOC)与DMPC脂质体的相互作用.结果表明,BPP与DMPC之间存在较强的疏水作用,从I_(2880cm)~(-1)/I_(2345cm)~(-1)强度比说明,BPP能使磷脂分子间协同作用加强,抑制由DOC所产生的磷脂分子间作用减弱.从C—C(?)动强度比I_(1998cm)~(-1)/I_((?)25cm)~(-1),说明BPP使磷脂分子内部gauche/trans构象比值下降,同时表现出抑制由DOC产生的guache/trans比值升高的作用.此外,BPP与DMPC作用后,磷脂头部基团外C—N伸缩振动波数向低波数向低波数方向从715cm~(-1)移至710cm~(-1),I_(715cm)~(-1)/I_(1295cm)~(-1)强度比值降低,提示BPP与DMPC之间除了有较强的疏水作用外,同间也存在静电相互作用.     

Study of the interaction between 8-azaguanine and bovine serum albumin using optical spectroscopy and molecular modeling methods

The interaction between 8-azaguanine (8-Azan) and bovine serum albumin (BSA) in Tris-HCl buffer solutions at pH 7.4 was investigated by means of fluorescence and ultraviolet-visible (UV-Vis) spectroscopy. At 298 K and 310 K, at a wavelength of excitation (λ _ex) of 282 nm, the fluorescence intensity decreased significantly with increasing concentrations of 8-Azan. Fluorescence static quenching was observed for BSA, which was attributed to the formation of a complex between 8-Azan and BSA during the binding reaction. This was illuminated further by the UV-Vis absorption spectra and the decomposition of the fluorescence spectra. The thermodynamic parameters ∆G, ∆H, ∆S were calculated. The results showed that the forces acting between 8-Azan and BSA were typical hydrophobic forces, and that the interaction process was spontaneous. The interaction distance r between 8-Azan and BSA, evaluated according to fluorescence resonance energy transfer theory, suggested that there is a high possibility of energy transfer from BSA to 8-Azan. Theoretical investigations based on homology modeling and molecular docking suggested that binding between 8-Azan and BSA is dominated by hydrophilic forces and hydrogen bonding. The theoretical investigations provided a good structural basis to explain the phenomenon of fluorescence quenching between 8-Azan and BSA.     

Multispectroscopic exploration and molecular docking analysis on interaction of eriocitrin with bovine serum albumin

Eriocitrin is a flavanone glycoside, which exists in lemon or lime citrus fruits. It possesses antioxidant, anticancer, and anti‐allergy activities. In order to investigate the pharmacokinetics and pharmacological mechanisms of eriocitrin in vivo, the interaction between eriocitrin and bovine serum albumin (BSA) was studied under the simulated physiological conditions by multispectroscopic and molecular docking methods. The results well indicated that eriocitrin and BSA formed a new eriocitrin‐BSA complex because of intermolecular interactions, which was demonstrated by the results of ultraviolet‐visible (UV‐vis) absorption spectra. The intrinsic fluorescence of BSA was quenched by eriocitrin, and static quenching was the quenching mechanism. The number of binding sites (n) and binding constant (K_b) at 310 K were 1.22 and 2.84 × 10⁶ L mol^?1, respectively. The values of thermodynamic parameters revealed that the binding process was spontaneous, and the main forces were the hydrophobic interaction. The binding distance between eriocitrin and BSA was 3.43 nm. In addition, eriocitrin changed the conformation of BSA, which was proved by synchronous fluorescence and circular dichroism (CD) spectra. The results of site marker competitive experiments suggested that eriocitrin was more likely to be inserted into the subdomain IIA (site I), which was further certified by molecular docking studies.     

Characterization of intermolecular interaction between cyanidin‐3‐glucoside and bovine serum albumin: Spectroscopic and molecular docking methods

The intermolecular interaction between cyanidin‐3‐glucoside (Cy‐3‐G) and bovine serum albumin (BSA) was investigated using fluorescence, circular dichroism and molecular docking methods. The experimental results revealed that the fluorescence quenching of BSA at 338 nm by Cy‐3‐G resulted from the formation of Cy‐3‐G–BSA complex. The number of binding sites (n) for Cy‐3‐G binding on BSA was approximately equal to 1. The experimental and molecular docking results revealed that after binding Cy‐3‐G to BSA, Cy‐3‐G is closer to the Tyr residue than the Trp residue, the secondary structure of BSA almost not change, the binding process of Cy‐3‐G with BSA is spontaneous, and Cy‐3‐G can be inserted into the hydrophobic cavity of BSA (site II′) in the binding process of Cy‐3‐G with BSA. Moreover, based on the sign and magnitude of the enthalpy and entropy changes (ΔH⁰ = – 29.64 kcal/mol and ΔS⁰ = – 69.51 cal/mol K) and the molecular docking results, it can be suggested that the main interaction forces of Cy‐3‐G with BSA are Van der Waals and hydrogen bonding interactions. Copyright © 2013 John Wiley & Sons, Ltd.     

In vitro study on binding interaction of quinapril with bovine serum albumin (BSA) using multi-spectroscopic and molecular docking methods

The binding interaction between quinapril (QNPL) and bovine serum albumin (BSA) in vitro has been investigated using UV absorption spectroscopy, steady-state fluorescence spectroscopic, synchronous fluorescence spectroscopy, 3D fluorescence spectroscopy, Fourier transform infrared spectroscopy, circular dichroism, and molecular docking methods for obtaining the binding information of QNPL with BSA. The experimental results confirm that the quenching mechanism of the intrinsic fluorescence of BSA induced by QNPL is static quenching based on the decrease in the quenching constants of BSA in the presence of QNPL with the increase in temperature and the quenching rates of BSA larger than 10¹⁰ L mol^?1 s^?1, indicating forming QNPL–BSA complex through the intermolecular binding interaction. The binding constant for the QNPL–BSA complex is in the order of 10⁵ M^?1, indicating there is stronger binding interaction of QNPL with BSA. The analysis of thermodynamic parameters together with molecular docking study reveal that the main binding forces in the binding process of QNPL with BSA are van der Waal’s forces and hydrogen bonding interaction. And, the binding interaction of BSA with QNPL is an enthalpy-driven process. Based on Förster resonance energy transfer, the binding distance between QNPL and BSA is calculated to be 2.76 nm. The results of the competitive binding experiments and molecular docking confirm that QNPL binds to sub-domain IIA (site I) of BSA. It is confirmed there is a slight change in the conformation of BSA after binding QNPL, but BSA still retains its secondary structure α-helicity.     

Deciphering binding mechanism between bovine serum albumin and new pyrazoline compound K4

The binding mechanism of a new and possible drug candidate pyrazoline derivative compound K4 and bovine serum albumin (BSA) was investigated in buffer solution (pH 7.4) using ultraviolet–visible light absorption and steady‐state and synchronous fluorescence techniques. The fluorescence intensity of BSA was quenched in the presence of K4 . The quenching process between BSA and K4 was examined at four different temperatures. Decrease of the quenching constants calculated using the Stern–Volmer equation and at increasing temperature suggested that the interaction BSA– K4 was realized through a static quenching mechanism. Synchronous fluorescence measurements suggested that K4 bounded to BSA at the tryptophan region. Fourier transform infrared spectroscopy results showed that there was no significant change in polarity around the tryptophan residue The forces responsible for the BSA– K4 interaction were examined using thermodynamic parameters. In this study, the calculated negative value of ΔG, the negative value of ΔH and the positive value of ΔS pointed to the interaction being through spontaneous and electrostatic interactions that were dominant for our cases. This study provides a very useful in vitro model to researchers by mimicking in vivo conditions to estimate interactions between a possible drug candidate or a drug and body proteins.     

Nanomechanics of opposing glycosaminoglycan macromolecules

In this study, the net intermolecular interaction force between a chondroitin sulfate glycosaminoglycan (GAG)-functionalized probe tip and an opposing GAG-functionalized planar substrate was measured as a function of probe tip-substrate separation distance in aqueous electrolyte solutions using the technique of high resolution force spectroscopy. A range of GAG grafting densities as near as possible to native cartilage was used. A long-range repulsive force between GAGs on the probe tip and substrate was observed, which increased nonlinearly with decreasing separation distance between probe tip and substrate. Data obtained in 0.1 M NaCl was well predicted by a recently developed Poisson-Boltzmann-based theoretical model that describes normal electrostatic double layer interaction forces between two opposing surfaces of end-grafted, cylindrical rods of constant volume charge density and finite length, which interdigitate upon compression. Based on these results, the nanomechanical data and interdigitated rod model were used together to estimate the electrostatic component of the equilibrium modulus of cartilage tissue, which was then compared to that of normal adult human ankle cartilage measured in uniaxial confined compression.     

Study on the interaction of chromate with bovine serum albumin by spectroscopic method

The interaction between two chromates [sodium chromate (Na₂CrO₄) and potassium chromate K₂CrO₄)] and bovine serum albumin (BSA) in physiological buffer (pH 7.4) was investigated by the fluorescence quenching technique. The results of fluorescence titration revealed that two chromates could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The apparent binding constants K and number of binding sites n of chromate with BSA were obtained by the fluorescence quenching method. The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) were negative, indicating that the interaction of two chromates with BSA was driven mainly by van der Waals forces and hydrogen bonds. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distance r between donor (BSA) and acceptor (chromate) was calculated based on Forster’s non-radiative energy transfer theory. The results of UV–Vis absorption, synchronous fluorescence, three-dimensional fluorescence and circular dichroism (CD) spectra showed that two chromates induced conformational changes of BSA.     

Spectroscopic and molecular docking studies on the interaction between N‐acetyl cysteine and bovine serum albumin

The interaction between N‐acetyl cysteine (NAC) and bovine serum albumin (BSA) was investigated by UV–vis, fluorescence spectroscopy, and molecular docking methods. Fluorescence study at three different temperatures indicated that the fluorescence intensity of BSA was reduced upon the addition of NAC by the static quenching mechanism. Binding constant (K_b) and the number of binding sites (n) were determined. The binding constant for the interaction of NAC and BSA was in the order of 10³ M^?1, and the number of binding sites was obtained to be equal to 1. Enthalpy (ΔH), entropy (ΔS), and Gibb's free energy (ΔG) as thermodynamic values were also achieved by van't Hoff equation. Hydrogen bonding and van der Waals force were the major intermolecular forces in the interaction process and it was spontaneous. Finally, the binding mode and the binding sites were clarified using molecular docking which were in good agreement with the results of spectroscopy experiments. © 2015 Wiley Periodicals, Inc. Biopolymers 103: 638–645, 2015.     

Studies on the interaction between Oxaprozin-E and bovine serum albumin by spectroscopic methods

The interaction between Oxaprozin-E and bovine serum albumin (BSA) was studied by spectroscopic methods including fluorescence and UV–vis absorption spectroscopy. The quenching mechanism of fluorescence of BSA by Oxaprozin-E was discussed to be a dynamic quenching procedure. The number of binding sites n and apparent binding constant K was measured by fluorescence quenching method. The thermodynamics parameter ΔH, ΔG, ΔS were calculated. The results indicate the binding reaction was mainly entropy-driven and hydrophobic forces played major role in the binding reaction. The distance r between donor (BSA) and acceptor (Oxaprozin-E) was obtained according to Förster theory of non-radioactive energy transfer.