离子液体双水相中PB与BSA的作用研究

运用荧光光谱,研究了在离子液体双水相体系中吡罗红B(PB)与牛血清白蛋白(BSA)的相互作用。结果表明,在离子液相中PB对BSA产生了荧光猝灭作用,且属于静态猝灭过程。计算得到在298K和308K下的结合常数分别为5.80×105Lomol-1和4.42×105Lomol-1,结合位点数分别为1.18和1.17。热力学参数表明PB与BSA之间的相互作用为静电作用力。用同步荧光法探讨了PB对BSA构象的影响。     

分子量为3000的壳聚糖与牛血清白蛋白相互作用的研究

在模拟人体生理条件下,利用荧光光谱、圆二色谱、紫外-可见吸收光谱法和三维荧光法研究了3 000分子量的壳聚糖(CS)与牛血清白蛋白(BSA)的相互作用。结果表明,CS对BSA的紫外吸收光谱具有增强作用,而对荧光光谱具有较强的荧光猝灭作用且峰位明显蓝移8~10 nm。用Stern-Volmer方程分别对实验数据进行分析,得出结论,CS对BSA的荧光猝灭作用是属于静态荧光猝灭;与其反应生成了新的复合物,发生了分子内的非辐射能量转移;并求得相互作用过程的结合常数KA(Kb)和热力学参数(ΔG、ΔH、ΔS),确定了它们之间的主要作用力是静电作用力,但疏水作用也不可忽略。圆二色谱、同步荧光光谱和三维荧光光谱法表明了CS对牛血清白蛋白的构象和所处的微环境发生了一定程度的变化。     

三维荧光光谱法和圆二色谱法研究氨基比林与牛血清白蛋白分子的相互作用

该文在模拟生理条件下,采用荧光光谱法、三维荧光光谱法以及圆二色谱法,研究氨基比林(PYM)与牛血清白蛋白(BSA)之间的相互作用。研究结果表明PYM对BSA有强烈的荧光猝灭作用,其荧光猝灭机制为静态猝灭。由热力学参数判定PYM和BSA的主要作用力为氢键和范德华力,并且相互作用是自发进行的。根据F觟rster的偶极-偶极非辐射能量转移理论可以得出PYM与BSA之间的结合距离为2.09 nm。利用三维荧光光谱和圆二色谱技术,分析PYM对BSA蛋白构象的影响,表明PYM与BSA相互作用后使BSA的微环境和构象发生改变。     

荧光光谱及分子模拟研究β-榄香烯与牛血清白蛋白的相互作用

在模拟生理p H条件(p H=7.40)下,用荧光光谱和分子模拟法研究β-榄香烯与牛血清白蛋白(BSA)的相互作用。在308 K和318 K温度下,激发波长(λex)为280 nm,测定BSA在340 nm的内源性荧光强度随着β-榄香烯浓度增加的变化,用分子对接方法研究β-榄香烯与牛血清白蛋白(BSA)的相互作用。β-榄香烯与牛血清白蛋白的反应机制为静态猝灭,作用力类型为疏水作用。分子模拟结果表明:β-榄香烯与牛血清白蛋白亚结构域A结合,二者之间有疏水作用和静电作用,且以疏水作用为主,这与荧光光谱结果一致。β-榄香烯与BSA具有较强的相互作用,以血清白蛋白为载体,β-榄香烯作为药物可通过血液循环到达病变部位,发挥药效。     

荧光光谱法研究桑色素与人血清白蛋白的相互作用

采用荧光猝灭光谱、紫外-可见吸收光谱研究了桑色素与人血清白蛋白(HSA)的结合作用。实验表明桑色素对HSA的荧光猝灭属于单一静态猝灭反应,在溶液中以摩尔比1:1牢固结合,各结合反应的平衡常数Kp>105,结合常数Kb>104;根据F rster非辐射能量转移机理,求算HSA与桑色素间距离r为3.81~3.58nm,能量转移效率E为0.18~0.13。并根据结合反应的热力学常数推测了药物与HSA之间的主要作用力类型为疏水作用力和偶极-偶极作用力。     

Pd(Ⅱ)与牛血清白蛋白相互作用的荧光光谱研究

采用荧光光谱法研究了Pd(Ⅱ)与牛血清白蛋白(BSA)的相互作用.使用高斯多峰拟合法对Pd(Ⅱ)-BSA体系荧光光谱的各荧光成分进行了解析.结果表明,BSA的荧光主要来源于色氨酸(Trp)残基,并推测Pd(Ⅱ)与BSA结合作用的位置在第212位Trp残基上.研究了Pd(Ⅱ)与BSA相互作用的荧光猝灭光谱,通过紫外吸收光谱的变化和猝灭速率常数Kq的比较对Pd(Ⅱ)与BSA相互作用的荧光猝灭机理进行了判别.结果表明,Pd(Ⅱ)对BSA的荧光猝灭属于静态猝灭.     

稀土荧光共聚物与蛋白质作用机理的光谱研究

用含铕稀土配合物单体成功地合成出含铕稀土荧光聚合物(PPNEu)。通过荧光光谱仪、紫外可见分光光度计研究了含铕稀土荧光聚合物与牛血清蛋白(BSA)的相互作用机理。结果表明:含铕稀土荧光聚合物能够与BSA相互结合,并使BSA出现荧光猝灭现象,该猝灭效应属于静态猝灭;结合常数和结合位点数分别为:KA=8.49×104 L/mol,n=1.25(298K);KA=7.45×104 L/mol,n=1.25(308K);在与BSA的结合过程中,吉布斯自由能(ΔG)为负值,熵变(ΔS)为正值且焓变(ΔH)为负值,说明静电力在PPNEu与BSA结合过程中起着主要作用。基于Frster理论,结合距离为3.38nm。     

牛血清白蛋白荧光猝灭法测定药物中的头孢硫脒

应用牛血清白蛋白(BSA)荧光猝灭法建立一种测定药物中头孢硫脒(C-18)物质量浓度的新方法.BSA具有很强的内源荧光性,而C-18溶液本身不产生荧光.当C-18与BSA结合后,会导致其荧光强度下降.BSA在λex=340 nm处结合C-18后的荧光猝灭强度与C-18的量在一定范围内呈良好的线性关系,据此建立测定药品中C-18含量的新方法.该结合物的最大发射波长为λmax=340 nm,与C-18摩尔浓度在2.5×10-6～3×10-5mol/L范围内线性关系良好.其线性回归方程为△F=2.177 95× 107CC-18-28.007,相关系数r=0.9962,检出限为1.60×10-6mol/L,RSD为0.24％～0.30％,加标回收率为94.36％～97.52％.该方法操作简便、快速,可用于实际样本的测定,结果满足要求.     

采用荧光光谱法研究DDAF与BSA的相互作用

研究新型反离子季铵盐DDAF与BSA的相互作用。通过单因素法,选出适宜的作用时间、Na+浓度和pH值;并采用荧光光谱法和三维荧光光谱法研究DDAF与BSA的相互作用机制。作用时间15 min、钠离子浓度为0.04 mol/L、pH值为待测液的初始pH值为适宜的实验条件;不同温度(290.15,296.15,303.15,310.15 K)下二者的双分子猝灭常数(Kq)分别为7.03×10~(10),8.53×10~(10),1.09×10~(11),1.12×10~(11) L/(mol·s);结合位点数(n)分别为1.17、0.84、0.97和1.02;?H和?S均大于0;三维荧光光谱显示,加入DDAF后,BSA的荧光峰发生蓝移,且荧光强度下降16.63%。DDAF和BSA为混合猝灭;二者以1∶1结合;二者间的作用力是疏水作用力;DDAF使BSA氨基酸残基周围的疏水环境增强。     

碳量子点的制备及与牛血清蛋白的相互作用

以木炭为碳源,分别采用回流、微波及超声等不同方法制备碳量子点(Carbon quantum dots,CQDs)。比较不同方法的优劣并优化反应条件、考察不同因素对其荧光量子产率的影响。得到最佳制备方法,制得粒径较小的荧光CQDs,用钝化剂PEG2000修饰后,提高其荧光寿命和量子产率。将修饰后的CQDs应用于与牛血清白蛋白(Bovine serum albumin,BSA)的相互作用,采用紫外吸收光谱法和荧光光谱法探讨其相互作用机理。结果表明,经回流法所制CQDs的荧光量子产率最高,其与BSA之间的荧光猝灭为静态猝灭过程。     

Spectroscopic and electrochemical studies on the molecular interaction between copper sulphide nanoparticles and bovine serum albumin

The interaction of covellite hexagonal phase of copper sulphide nanoparticles (CuS NPs) with bovine serum albumin (BSA) was examined systematically by using fluorescence, UV–visible, circular dichroism (CD), Fourier transform infrared (FTIR), dynamic light scattering (DLS) and molecular modelling techniques. Electrochemical method was studied to further confirm the interaction of BSA with CuS NPs. The results of fluorescence studies demonstrated that fluorescence of BSA was quenched by CuS NPs via a static quenching mechanism. The negative values of thermodynamic parameters (ΔG, ΔH and ΔS) indicated that the binding process is spontaneous, exothermic and van der Waals force or hydrogen bonding plays major roles in the interaction of CuS NPs with BSA. The interaction of CuS NPs with Trp residue was established by synchronous studies, and competitive binding studies revealed that Trp-212 of subdomain IIA was involved in the interaction with these nanoparticles. Further, the efficiency of energy transferred and the distance between fluorophore (BSA) and acceptor (CuS NPs) were calculated using Forster’s resonance energy transfer theory. The results of UV–visible, CD, FTIR and DLS revealed that the CuS NPs interact with BSA by inducing the conformational changes in secondary structure and reducing the α-helix content of BSA. Molecular modelling studies suggested that CuS NPs bind to site I of sub domain IIA of BSA. The results of spectroscopic and molecular docking studies were complimented by the electrochemical techniques.     

Study on protein conformation and adsorption behaviors in nanodiamond particle-protein complexes

In the present research, the conformation of bovine serum albumin (BSA) in the nanodiamond particle (ND)-BSA complex was studied by Fourier transform infrared spectroscopy, fluorescence spectroscopy, UV-vis spectroscopy, and circular dichroism spectroscopy. The spectroscopic study revealed that most BSA structural features could be preserved in the complex though the BSA underwent conformational changes in the complex due to ND-BSA interaction. In addition, BSA adsorption isotherms and zeta-potential measurements were employed to investigate the pH dependence of the ND-BSA interaction. The changes in surface charge of the ND-BSA complex with pH variations indicated that the binding of BSA to ND might lead to not only the adsorption of BSA onto the ND surface but also the partial breakup of ND aggregates into relatively small ND-BSA aggregates because of the strong binding force between ND and BSA. The results show that ND is an excellent platform for protein immobilization with high affinity and holds great potential to be used for biosensor applications.     

Interaction of malachite green with bovine serum albumin: determination of the binding mechanism and binding site by spectroscopic methods

The interaction between malachite green (MG) and bovine serum albumin (BSA) under simulative physiological conditions was investigated by the methods of fluorescence spectroscopy, UV-vis absorption and circular dichroism (CD) spectroscopy. Fluorescence data showed that the fluorescence quenching of BSA by MG was the result of the formation of the MG-BSA complex. According to the modified Stern-Volmer equation, the effective quenching constants (K(a)) between MG and BSA at four different temperatures were obtained to be 3.734 x 10(4), 3.264 x 10(4), 2.718 x 10(4), and 2.164 x 10(4)L mol(-1), respectively. The enthalpy change (Delta H) and entropy change (DeltaS) were calculated to be -27.25 kJ mol(-1) and -11.23 J mol(-1)K(-1), indicating that van der Waals force and hydrogen bonds were the dominant intermolecular force in stabilizing the complex. Site marker competitive experiments indicated that the binding of MG to BSA primarily took place in sub-domain IIA. The binding distance (r) between MG and the tryptophan residue of BSA was obtained to be 4.79 nm according to F?rster theory of non-radioactive energy transfer. The conformational investigation showed that the presence of MG decreased the alpha-helical content of BSA (from 62.6% to 55.6%) and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of BSA molecules.     

Characterization of the interaction between 4-(tetrahydro-2-furanmethoxy)-N-octadecyl-1,8-naphthalimide and human serum albumin by molecular spectroscopy and its analytical application

A novel 4-(tetrahydro-2-furanmethoxy)-N-octadecyl-1,8-naphthalimide (TNN) was synthesized as a spectrofluorimetric probe for the determination of proteins. The effect of different solvents on the spectral characteristics of TNN was investigated. The results showed that TNN displayed dependent solvent polarity properties due to the effect of internal charge transfer. The interactions between TNN and human serum albumin (HSA) were studied by fluorescence and absorption spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by TNN was the result of the formation of TNN-HSA complex. The binding parameters of interactions between TNN and HSA at different temperatures were obtained according to the Stern-Volmer equation. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS), for the interactions were calculated to be -7.31 kJ mol(-1) and 72.75 J mol(-1) K(-1) according to the van't Hoff equation, indicating that the hydrogen bonds and hydrophobic interactions were the dominant intermolecular force in stabilizing the complex. The effect of TNN on the conformation of HSA was analyzed by circular dichroism and synchronous fluorescence spectroscopy. Furthermore, the results of displacement experiments using warfarin indicated that TNN could bind to site I of HSA. The fluorescence of TNN could be largely quenched by HSA, based on which a new fluorometric method for detecting HSA in the HCl-Tris buffer solution (pH = 7.4) was developed. The linear ranges of the calibration curves were 0.1~14.2 μM for HSA, 0.1~13.0 μM for bovine serum albumin (BSA), 0.2~9.7 μM for γ-globulin, and 0.3~11.3 μM for hemoglobin (Hb), with detection limits (3σ) of 1.37 × 10(-10) M for HSA, 1.84 × 10(-10) M for BSA, 3.14 × 10(-10) M for γ-globulin, and 6.86 × 10(-10) M for Hb. The effect of metal cations on the fluorescence spectra of TNN in ethanol was also investigated. The method has been applied to the determination of total proteins in human serum samples collected from the hospital and the results were in good agreement with those reported by the hospital.     

Changes in porphyrin nonlinear absorption owing to interaction with bovine serum albumin

The changes in the nonlinear absorption of meso-tetrakis (p-sulfonatophenyl) porphyrin (TPPS(4)) caused by its binding to bovine serum albumin (BSA) were investigated in aqueous solutions. The nonlinear absorption depended on the excitation wavelength and pH. It is noteworthy that, for excitation at 640 nm, saturated absorption was observed in a TPPS(4) solution (pH 4.0), whereas reverse saturated absorption occurred for all pH values from 4.0 to 7.0 when BSA was added to TPPS(4). The presence of BSA also initiates an increase in the saturation intensity and a reduction of the nonlinear absorption coefficient. The interpretation of the results based on the binding of TPPS(4) to BSA is corroborated by linear absorption, fluorescence, light scattering, and flash-photolysis data.     

Probing the interaction of bovine haemoglobin with gold nanoparticles

The interaction between gold nanoparticles (GNPs) and bovine haemoglobin (BHb) was studied by ultraviolet-visible (UV-Vis) absorption, circular dichroism (CD) and fluorescence spectroscopic techniques. The UV-Vis absorption spectrum demonstrated that there was interaction between GNPs and BHb, but no direct interaction between GNPs and haem groups of BHb. The fluorescence data revealed that GNPs effectively quenched the intrinsic fluorescence of BHb via static quenching. The binding of GNPs to BHb occurred at a single site. The binding process was a spontaneous molecular interaction procedure, in which hydrophobic force and hydrogen bonds played a major role. The alternations of protein secondary structure in the presence of GNPs were also determined by CD spectroscopy. This work is helpful to understand the interaction mechanism of GNPs with haemoglobin, which can guide the applications of GNPs in biomedicine.     

Characterization of Alizarin Red S binding sites and structural changes on human serum albumin: a biophysical study

Alizarin Red S (ARS), is a water-soluble, widely used anthraquinone dye synthesized by sulfonation of alizarin. In this report, the binding of ARS to human serum albumin (HSA) was characterized by employing fluorescence, UV/vis absorption, circular dichroism (CD), and molecular modeling methods. The data of fluorescence spectra displayed that the binding of ARS to HSA is the formation of HSA-ARS complex at 1:1 stoichiometric proportion. Hydrophobic probe 8-anilino-1-naphthalenesulfonic acid (ANS) was employed and elucidated that the dye was located in subdomain IIIA. This phenomenon corroborates the result of site-specific probe displacement experiments, which demonstrate the dye is at indole-benzodiazepine site (Sudlow's site II); and it is also consistent with guanidine hydrochloride (GuHCl) induced HSA unfolding studies and molecular modeling simulations. The features of the dye, which led to structural perturbations of HSA, have also been studied in detail by methods of UV/vis, CD and three-dimensional fluorescence spectroscopy.     

Direct visualization of RecQ helicase–DNA interaction with fluorescence microscopy and atomic force microscopy

RecQ helicase–DNA interactions were directly visualized with fluorescence microscopy. DNA–RecQ complexes formed in binding and unwinding reaction were stretched onto the hydrophobic surface by molecular combing method. The complexes can be observed with fluorescence microscope because the DNA molecules were labeled with dye molecules of YOYO-1. The DNA binding and unwinding activity of RecQ helicase leads to reduced lengths of the observed DNA molecules. More direct observations with atomic force microscopy were also made. It was seen that RecQ is mainly monomeric both in solution and after binding to DNA.     

A spectroscopic study on the interaction between gold nanoparticles and hemoglobin

The interaction between horse hemoglobin and gold nanoparticles was studied using optical spectroscopy. UV-vis and fluorescence spectra show that a spontaneous binding process occurred between hemoglobin and gold nanoparticles. The Soret band of hemoglobin in the presence of gold nanoparticles does not show significant changes, which proves that the protein retained its biological function. A shift to longer wavelengths appears in the plasmonic band of gold nanoparticles upon the attachment of hemoglobin molecules. Gold nanoparticles quench the fluorescence emission of tryptophan residues in the structure of hemoglobin. The Stern-Volmer quenching constant, the binding constant and the number of binding sites were also calculated. Thermodynamic parameters indicate that the binding was mainly due to hydrophobic interactions.