Study on the binding of luteolin to bovine serum albumin

Binding of luteolin (LU) to bovine serum albumin (BSA) was investigated at 298, 308 and 318K at pH 7.4 using spectrophotometric techniques such as fluorescence emission, circular dichroism (CD). The data obtained from fluorescence quenching experiments showed that LU was bound to BSA and binding constants and the number of binding sites (n approximately 1) were obtained. The thermodynamic parameters DeltaH(0), DeltaS(0), DeltaG(0) at different temperatures were calculated. They indicated that both hydrophobic forces and hydrogen bonds are the major interactions between LU and BSA. A value of 3.12nm for the average distance r between LU (acceptor) and tryptophan residue (Trp) of BSA (donor) was derived from the fluorescence resonance energy transfer. The effects of some common metal ions on the binding are also considered. Besides, the interaction of BSA with LU led to a change in the conformation of BSA.     

Thermodynamic and structural changes associated with the interaction of a dirhamnolipid biosurfactant with bovine serum albumin

The interaction of a dirhamnolipid biosurfactant secreted by Pseudomonas aeruginosa with bovine serum albumin was studied by means of various physical techniques. Binding of the biosurfactant to bovine serum albumin was first characterized by isothermal titration calorimetry, showing that one or two molecules of dirhamnolipid, in the monomer state, bound to one molecule of the protein with high affinity. These results were confirmed by surface tension measurements in the absence and presence of bovine serum albumin. As seen by differential scanning calorimetry, dirhamnolipid shifted the temperature of the thermal unfolding of bovine serum albumin toward higher values, thus increasing the stability of the protein on heating. The impact of dirhamnolipid on the structure of the native protein was low, since most of the secondary structure remained unaffected upon interaction with the biosurfactant, as shown by FTIR spectroscopy. However, 2D correlation infrared spectroscopy indicated that the sequence of temperature-induced structural changes in native bovine serum albumin was modified by the presence of the biosurfactant. The consequences of these results in relation to possible applications of these dirhamnolipid biosurfactants for protein studies are discussed.     

Study on the binding behavior of bovine serum albumin with cephalosporin analogues by chemiluminescence method

The luminol-bovine serum albumin chemiluminescence system was proposed for the first time. It was found that the hydrophilic luminol bound to the hydrophilic domain at Trp¹³⁴ of BSA with accelerating the electrons transferring rate of excited 3-aminophthalate, which led to the enhancement CL intensity of luminol at 425 nm. The increment of chemiluminescence intensity was proportional to the concentrations of bovine serum albumin from 5.0 × 10⁻¹¹ to 1.0 × 10⁻⁸ mol L⁻¹ with the linear equation of ΔI = 7.47C_BSA + 4.89 (R² = 0.9950). Based on the remarkable quenching effect of cephalosporin on the luminol-bovine serum albumin chemiluminescence system, the interaction of bovine serum albumin-cephalosporin was studied by flow injection-chemiluminescence method. A valuable model for studying the interaction of bovine serum albumin-cephalosporin was constructed and the formula lg[(I₀ − I)/I] = lg K_D + n lg[D] was obtained. The binding parameters calculated by the model did agree very well with the results obtained by fluorescence quenching method. The major binding force of bovine serum albumin with cephalosporins was the hydrophobic effect. The binding ability of cephalosporin analogues to bovine serum albumin followed the pattern: cefoperazone, ceftriaxone and cefotaxime > cefuroxime and cefaclor > cefadroxil, cefradine and cefazolin, which was close to the order of their antibacterial ability. Using flow injection chemiluminescence method also obtained the stoichiometric ratio, the average of association constant K_P and dissociation degree α of luminol-bovine serum albumin were 1:1, 1.12 × 10⁷ L mol⁻¹ and 0.086, respectively.     

Study of binding interaction of rivaroxaban with bovine serum albumin using multi-spectroscopic and molecular docking approach

Background

Rivaroxaban is a direct inhibitor of coagulation factor Xa and is used for venous thromboembolic disorders. The rivaroxaban interaction with BSA was studied to understand its PK and PD (pharmacokinetics and pharmacokinetics) properties. Multi-spectroscopic studies were used to study the interaction which included UV spectrophotometric, spectrofluorometric and three dimensional spectrofluorometric studies. Further elucidation of data was done by molecular simulation studies to evaluate the interaction behavior between BSA and rivaroxaban.

Results

Rivaroxaban quenched the basic fluorescence of BSA molecule by the process of static quenching since rivaroxaban and BSA form a complex that results in shift of the absorption spectra of BSA molecule. A decline in the values of binding constants was detected with the increase of temperatures (298–308 K) and the binding constants were in range from 1.32 × 10⁵ to 4.3 × 10³ L mol^?1 indicating the instability of the BSA and rivaroxaban complex at higher temperatures. The data of number of binding sites showed uniformity. The site marker experiments indicated site I (sub-domain IIA) as the principal site for rivaroxaban binding. The thermodynamic study experiments were carried at the temperatures of 298/303/308 K. The ?G⁰, ?H⁰ and ?S⁰ at these temperatures ranged between ? 24.67 and ? 21.27 kJ mol^?1 and the values for ?H⁰ and ?S⁰ were found to be ? 126 kJ mol^?1 and ?S ? 340 J mol^?1 K^?1 The negative value of ?G⁰ indicating spontaneous binding between the two molecules. The negative values in ?H⁰ and ?S⁰ indicated van der Waals interaction and hydrogen bonding were involved during the interaction between rivaroxaban and BSA.

Conclusions

The results of molecular docking were consistent with the results obtained from spectroscopic studies in establishing the principal binding site and type of bonds between rivaroxaban and BSA.

     

荧光光谱法研究左西孟旦与牛血清白蛋白的结合反应

用荧光光谱法、分光光度法研究了水溶液中左西孟旦与牛血清白蛋白(BSA)的相互结合反应。研究表明:左西孟旦对BSA的内源荧光有较强的猝灭作用且该猝灭作用属于静态荧光猝灭作用。得出了反应的结合常数(KA=1.48×106L/mol)和结合位点数(n=1.14)。根据Frster非辐射能量转移机理,求算了给体(BSA)与受体(左西孟旦)间距离r=2.9 nm和能量转移效率E=0.33。     

Temperature dependence on the binding of butyl orange by bovine serum albumin

The binding of 4′-dibutylaminoazobenzene-4-sulfonate anion (butyl orange) by bovine serum albumin has been examined quantitatively by an equilibrium dialysis method at 5, 10, 15, 20, 25, and 35°C. The first binding constants and the thermodynamic parameters for the formation of the first dye anion-protein complex have been calculated. The peculiar temperature dependence of the first binding constant could be observed. That is, the value of the first binding constant increases with increasing temperature until it reaches a maximum value at approximately 18°C and then decreases with raising temperature. Accordingly, this binding process is exothermic above 18°C and is endothermic below 18°C. Near 18°C the process exhibits athermal reaction. From the thermodynamic data obtained, it is evident that the favorable free energy of the binding is accompanied by an entropy gain and that the enthalpies of the binding vary from a positive (unfavorable) value below 18°C to a negative (favorable) one above 18°C. Furthermore an apparent temperature dependence of the thermodynamic functions was observed. That is, ΔF° becomes larger in absolute magnitude as the temperature increases. The positive quantity of ΔS° tends to decrease with increasing temperature. All these facts can be interpreted satisfactorily in terms of hydrophobic interactions between hydrophobic portions of the dye and nonpolar parts of the albumin.     

光谱法研究染料木素与牛血清白蛋白的相互作用

采用荧光和紫外-可见吸收光谱,研究了染料木素与牛血清白蛋白(BSA)的相互作用.结果表明染料木素对BSA有较强的荧光猝灭作用;根据Stern-Volmer方程得到染料木素与BSA之间的结合常数KA为4.37×106(27 ℃)、6.45×10b(37℃)和6.76×106(47℃).根据Forster非辐射能量转移理论,求出了染料木素与BSA之间的结合距离为2.64 nm(27℃)、2.68mm(37℃)和2.71 nm(47℃).热力学数据表明该药物与牛血清白蛋白的相互作用是一个吉布斯自由能降低的自发过程,且二者之间的主要作用力类型为静电引力,同时用同步荧光光谱探讨了染料木素对BSA构象的影响.     

大豆苷元与牛血清白蛋白的相互作用研究

采用荧光和紫外-可见吸收光谱,研究了大豆苷元与牛血清白蛋白(BSA)的相互作用.结果表明大豆苷元对BSA有较强的荧光猝灭作用;根据Stern-Volmer方程得到大豆苷元与BSA之间的结合常数KA为0.385×105 (30℃)、0.405×105(40℃)和0.431×105(50℃).根据F(o)rster非辐射能量转移理论,求出了大豆苷元与BSA之间的结合距离为2.34 nm(30℃)、2.48 nm(40℃)和2.71 nm(50℃).热力学数据表明大豆苷元与BSA之间的作用力主要为疏水作用力,同时用同步荧光光谱探讨了大豆苷元对BSA构象的影响.     

壳聚糖镍与牛血清白蛋白相互作用的研究

采用紫外吸收、荧光和红外光谱,研究了壳聚糖镍与牛血清白蛋白(BSA)的相互作用。结果表明:随着壳聚糖镍浓度的增加,BSA的紫外光谱表现增色效应和较小的蓝移;壳聚糖镍可以猝灭BSA的内源荧光,其猝灭机理属于静态猝灭。在室温下,壳聚糖镍与BSA的的结合常数KA为7.08×106。     

光谱法研究尼泊金乙酯钠与牛血清白蛋白的相互作用

在模拟生理条件下(pH=7.40),应用荧光光谱、吸收光谱和同步荧光光谱法探讨了不同温度下尼泊金乙酯钠(Ethylparaben Sodium,EPS)与牛血清白蛋白(Bovine Serum Albumin,BSA)相互作用的机制.荧光光谱和吸收光谱分别表明:尼泊金乙酯钠对BSA内源荧光有明显猝灭作用,属于静态猝灭,二者的猝灭作用是由于尼泊金乙酯钠与BSA形成基态复合物导致的.运用双对数方程求得291、310 K时的结合常数分别为3.23×106、3.63×105L·mol-1,结合位点数分别为0.99和0.84.运用热力学方程得出热力学参数(ΔH,ΔS),通过ΔH0,ΔS0可知二者之间的作用力主要是氢键或范德华力.同步荧光光谱表明尼泊金乙酯钠对BSA结构的构象会产生影响.本研究为EPS的毒理和生物学效应提供了重要的参考信息.     

Study on the binding of puerarin to bovine serum albumin by isothermal titration calorimetry and spectroscopic approaches

The interaction of a flavonoid molecule (puerarin) with bovine serum albumin (BSA) was characterized by isothermal titration calorimetry (ITC), optical spectroscopic technique, and molecular modeling method under physiological conditions. The binding parameters for the reaction were calculated according to ITC experiments at different temperatures. The thermodynamic parameters, negative enthalpy changes (ΔH), and positive entropy (ΔS) indicated that the binding processes were entropically driven. The alterations of protein secondary structure in the presence of puerarin in aqueous solution were estimated by the evidences from FT-IR and CD spectroscopy with reductions of α-helices. On the basis of fluorescence resonance energy transfer (FRET) between excited tryptophan in BSA and BSA bound puerarin, the critical transfer distance and mean distance between tryptophan in BSA and puerarin were estimated.     

甲基紫与牛血清白蛋白作用的荧光光谱研究

在pH 7.40的Tris-HC1缓冲溶液体系中,采用荧光光谱法和同步荧光光谱法研究了甲基紫(MV)与牛血清白蛋白(BSA)相互作用.结果表明MV与BSA相互作用两者存在一个结合位点,结合常数(KA)为7.628×103 L/mol,MV与BSA主要发生疏水作用,反应是一个吸热、熵增的自发过程.     

Study of the interaction of indirubin with bovine serum albumin

This study examined the interaction of indirubin with bovine serum albumin (BSA) at three temperatures (286, 297, 308 K) at pH 7.40. In the presence of indirubin, the drug-BSA binding mode, binding constant and the protein structure changes in aqueous solution were determined by fluorescence quenching methods including Fourier transform infrared (FT-IR) spectroscopy and UV-Vis spectroscopy. The FT-IR change indicates that indirubin binds to BSA. The change in protein secondary structure accompanying ligand binding has been proved by fluorescence spectra data. The thermodynamic parameters, the enthalpy change (DeltaH), and the entropy change (DeltaS) calculated by the van't Hoff equation possess small negative (-2.744 kJ.mol(-1)) and positive values (112.756 J.mol(-1).K(-1)), respectively, which indicated that hydrophobic interactions play the main role in the binding of indirubin to BSA. Furthermore, the displacement experiment shows that indirubin can bind to the subdomain IIA and the distance between the tryptophan residues in BSA and indirubin bound to site I was estimated to be 2.24 nm according to F?ster's equation on the basis of fluorescence energy transfer.     

Thermodynamics of binding cationic detergents to bovine serum albumin

Molar ratio (Γ_a) for binding cetyl trimethyl ammonium bromide (CTAB), myristyl trimethyl ammonium bromide (MTAB), dodecyl trimethyl ammonium bromide (DTAB) and cetyl pyridinium chloride (CPCL) to globular protein bovine serum albumin have been measured by equilibrium dialysis technique under various conditions of pH, ionic strength and temperatures. In all cases binding isotherms are S-shaped and at high concentrations of an amine, Γ_a appears to reach a constant value Γ^m_a, Γ^m_a may vary from 1 to 836 depending upon temperature, nature of amines and other solution parameters. The standard free energy changes (ΔG°) for BSA-amine binding have been calculated using appropriate reference states. The order of ΔG° for various systems is found to be in agreement with the order of the maximum extent of binding Γ^m_a. The effects of chain length of the surfactants on ΔG° and Γ^m_a are found to be irregular. ΔS° and ΔH° for binding reactions are also found to be significant in magnitude. Binding interactions at various pH and ionic strengths do not exhibit regularities in terms of electrostatic effects. All these observations lead to the conclusion that the binding sites of BSA are highly heterogeneous so that binding interactions become irregular in nature. All types of interactions are involved in the binding process so that the mechanism of binding in an individual system is complex in nature. The thermal stability and intrinsic viscosity of bovine serum albumin in the presence of amines have been examined in the light of the binding process.     

Thyroxine binding properties of glycosylated bovine serum albumin.

Thyroid hormone, thyroxine (T4) binding properties of glycosylated bovine serum albumin (G-BSA), and intact BSA were studied by the fluorescence method. The apparent binding constants for intact BSA were 0.8 (0.16) x 10(6) M-1 at pH 5.0 and 2.18 (0.06) x 10(6) M-1 at pH 9.5 at 25 degrees C. T4 binding for G-BSA was independent of pH and the apparent binding constant was 1.4 x 10(6) M-1. Thermodynamic parameters were also evaluated from the Van't Hoff plots of the apparent binding constants at pH 7.4 and 8.5. At both pH's, the free energy, enthalpy and entropy changes were almost the same for both G-BSA and BSA.     

Spectroscopic study on the inherent binding information of cationic perfluorinated surfactant with bovine serum albumin

UV-vis, FT-IR, fluorescence and synchronous fluorescence spectra are applied to discuss the inherent binding information of model protein bovine serum albumin (BSA) with perfluorinated surfactant trimethyl-1-propanaminium iodide (FC-134). According to the results analyzed from Stern-Volmer equation, FC-134 can quench the fluorescence intensity of BSA via a dynamic quenching mechanism with complex formation. The thermodynamic parameters are calculated, revealing that hydrophobic force is the main interaction driven force. The binding constants and number of binding sites are also obtained. With the aid of site markers—warfarin and ibuprofen, we first report that FC-134 primarily binds to tryptophan residue Trp-214 of BSA within site I (sub-domain IIA).     

Study on the interaction between antibacterial drug and bovine serum albumin: A spectroscopic approach

The binding of sulfamethoxazole (SMZ) to bovine serum albumin (BSA) was investigated by spectroscopic methods viz., fluorescence, FT-IR and UV–vis absorption techniques. The binding parameters have been evaluated by fluorescence quenching method. The thermodynamic parameters, ΔH°, ΔS°and ΔG° were observed to be −58.0 kJ mol⁻¹, −111 J K⁻¹ mol⁻¹ and −24 kJ mol⁻¹, respectively. These indicated that the hydrogen bonding and weak van der Waals forces played a major role in the interaction. Based on the Forster's theory of non-radiation energy transfer, the binding average distance, r, between the donor (BSA) and acceptor (SMZ) was evaluated and found to be 4.12 nm. Spectral results showed the binding of SMZ to BSA induced conformational changes in BSA. The effect of common ions and some of the polymers used in drug delivery for control release was also tested on the binding of SMZ to BSA. The effect of common ions revealed that there is adverse effect on the binding of SMZ to BSA.     

Structural relationship and binding mechanisms of five flavonoids with bovine serum albumin

Flavonoids are structurally diverse and the most ubiquitous groups of dietary polyphenols distributed in various fruits and vegetables. In this study, the interaction between five flavonoids, namely formononetin-7-O-β-D-glucoside, calycosin- 7-O-β-D-glucoside, calycosin, rutin, and quercetin, and bovine serum albumin (BSA) was investigated by fluorescence and UV-vis absorbance spectroscopy. In the discussion, it was proved that the fluorescence quenching of BSA by flavonoids was a result of the formation of a flavonoid-BSA complex. Fluorescence quenching constants were determined using the Stern-Volmer and Lineweaver-Burk equations to provide a measure of the binding affinity between the flavonoids and BSA. The binding constants ranked in the order quercetin>rutin>calycosin>calycosin-7-O-β-D-glucoside ≈ formononetin-7-O-β-D-glucoside. The results of thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures indicated that the hydrophobic interaction played a major role in flavonoid-BSA association. The distance r between BSA and acceptor flavonoids was also obtained according to F?rster's theory of non-radiative energy transfer.