蛋白质与刚果红结合反应的研究

研究了酸性溶液中蛋白质(BSA)与刚果红(CGR)的结合反应。BSA与CGR相互作用形成复合物,溶液颜色由蓝色变为红色,最大吸收波长紫移,表明在蛋白质正电荷作用下,CGR由游离态酸色型变为结合态碱色型。测得CGR与BSA的结合最大结合数约为43,符合Scatchard模型。荧光光谱表明,CGR与BSA作用导致BSA荧光猝灭,结合位点为BSA第212位色氨酸残基,相互作用为非辐射能量转移。     

牛血清白蛋白与偶氮胂Ⅲ-镱?结合反应及其应用

研究了在酸性溶液中BSA与偶氮胂Ⅲ-镱(Ⅲ)络合物的结合反应.发现加入BSA后偶氮胂Ⅲ-镱?的吸收光谱产生减色效应和红移,探讨了实验条件对结合反应的影响.随着BSA量的增加,650 nm吸收峰线性下降,基于此建立了蛋白质定量分析方法,并运用于实际样品的测定,结果与紫外分光光度法测得的结果吻合.用分光光度法研究BSA与偶氮胂Ⅲ-镱?之间的结合模型,发现结合反应符合Scatchard模型.进一步的研究发现BSA与阳离子表面活性剂、偶氮胂Ⅲ-镱?之间的作用机理相类似.     

银纳米线与BSA相互作用的光谱学研究

主要研究了粒径为60 nm的银纳米线与牛血清白蛋白(BSA)之间的相互作用.利用紫外可见吸收光谱法和荧光光谱法对反应体系进行了光谱学实验研究.实验结果表明,随着银纳米线溶液浓度的增加,反应体系的紫外吸收峰强度增大.但是,荧光强度却明显猝灭.由荧光结果可以得知银纳米线和BSA的相互作用过程是静态猝灭;同步荧光光谱结果表明,银纳米线对蛋白质周围的环境产生了影响.由变温荧光实验结果还可获得银纳米线与BSA相互作用的结合常数、结合位点数以及吉布斯自由能变.由热力学数据可知银纳米与牛血清白蛋白可以自发结合发生反应,且主要结合力为范德华力和氢键.     

蒽醌及黄酮类化合物与牛血清白蛋白结合的反应研究

用离心超过滤法测定了十四种不同结构的蒽醌及黄酮类化合物与牛血清白蛋白(BSA)的结合常数和结合部位数目,发现这些化合物与BSA 的结合能力随其脂溶性增加而增大,龙胆苦苷不与BSA结合,研究了L-色氨酸,油酸与大黄素对BSA 的竞争结合反应,结果表明L-色氨酸和大黄素拥有一个相同的强结合部位,可以发生1:1 置换反应.低浓度油酸存在下使大黄素等同的6个结合部位区分为两类:n~1=2,n~2=4, 结合部位数目不变,但结合常数显著减小,油酸浓度足够大时,大黄素完全不与BSA结合,测得大黄素与BSA结合的△H≈0.根据上述结果,对蒽醌及黄酮类化合物与BSA结合反应的机理进行了初步探讨.     

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。     

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.     

小檗碱与牛血清白蛋白相互作用的核磁共振研究

采用核磁共振波谱技术(NMR)研究小檗碱与牛血清白蛋白(BSA)的相互结合作用.比较不同浓度小檗碱在一定浓度的BSA溶液中的化学位移、弛豫时间和扩散系数的变化情况.研究表明,小檗碱环上芳香质子与BSA的结合作用较强,其它烷基质子与BSA结合作用较弱;BSA的结合使得小檗碱各个质子的1HT1弛豫时间明显减少,质子在溶液中...     

蒽醌及黄酮类化合物与牛血清白蛋白结合的反应的光谱研究

用停留技术研究了大黄素与牛血清白蛋白(BSA)结合反应的动力学.发现在25℃,pH10.0时结合在场100ms即可达到平衡.大黄素等7种蒽醌及黄酮类化合物与BSA 结合后,可见区最大吸收波长红移.吸收强度增加. 荧光光谱研究表明. 这些化合物对BSA荧光有很强的猝灭作用.根据猝灭结果, 求出了它们与BSA 的结合常数, 并基于Forster非辐射能量转移机理,计算了它们的第一结合部位与BSA中212- 色氨酸残基的距离.提出了蒽醌及黄酮类化合物与BSA形成复合物的结构模型.     

蒽醌及黄酮类化合物与牛血清的蛋白结合反应的光谱研究

用停留技术研究了大黄素与牛血清白蛋白(BSA)结合反应的动力学,发现在25℃,pH10.0时结合在100ms即可达到平衡.大黄素等7种蒽醌及黄酮类化合物与BSA结合后,可见区最大吸收波长红移,吸收强度增加.荧光光谱研究表明,这些化合物对BSA荧光有很强的猝灭作用.根据猝灭结果,求出了它们与BSA的结合常数,并基于F(?)rster非辐射能量转移机理,计算了它们的第一结合部位与BSA中212-色氨酸残基的距离.提出了蒽醌及黄酮类化合物与BSA形成复合物的结构模型.     

蒽醌及黄酮类化合物与牛血清白蛋白结合的反应的光谱研究

用停留技术研究了大黄素与牛血清白蛋白(BSA)结合反应的动力学.发现在25℃,pH10.0时结合在场100ms即可达到平衡.大黄素等7种蒽醌及黄酮类化合物与BSA 结合后,可见区最大吸收波长红移.吸收强度增加. 荧光光谱研究表明. 这些化合物对BSA荧光有很强的猝灭作用.根据猝灭结果, 求出了它们与BSA 的结合常数, 并基于Forster非辐射能量转移机理,计算了它们的第一结合部位与BSA中212- 色氨酸残基的距离.提出了蒽醌及黄酮类化合物与BSA形成复合物的结构模型.     

Electrochemical studies of the interaction of tetraphenylporphyrin tetrasulfonate (TPPS) with albumin

An electrochemical investigation of the interaction of TPPS with BSA on a Hg electrode is reported for the first time. The addition of BSA to TPPS solution results in a decrease of both the reduction and the oxidation current with no change of the peak potentials. In presence of BSA, no new peaks appear, and the standard rate constant k _s is not significantly changed. The reaction of TPPS with BSA yields a kind of supramolecular complex TPPS-BSA, which is electrochemically non-active. The equilibrium constant for the complex has been calculated. The decrease of the peak current can be used to determine BSA concentrations. Received: 2 August 1998 / Revised: 21 September 1998 / Accepted: 24 September 1998     

Electrochemical studies of the interaction of tetraphenylporphyrin tetrasulfonate (TPPS) with albumin

An electrochemical investigation of the interaction of TPPS with BSA on a Hg electrode is reported for the first time. The addition of BSA to TPPS solution results in a decrease of both the reduction and the oxidation current with no change of the peak potentials. In presence of BSA, no new peaks appear, and the standard rate constant k _s is not significantly changed. The reaction of TPPS with BSA yields a kind of supramolecular complex TPPS-BSA, which is electrochemically non-active. The equilibrium constant for the complex has been calculated. The decrease of the peak current can be used to determine BSA concentrations. Received: 2 August 1998 / Revised: 21 September 1998 / Accepted: 24 September 1998     

Preparation of Functional Fluorescent Microspheres Used for HTS and Their Interaction with Biomolecules

There is considerable interest in protein adsorption onto microspheres because of its importance in a wide range of biomedical applications, such as artificial tissues and organs, drug delivery systems, biosensors, solid-phase immunoassays, immunomagnetic cell separation and immobilized enzymes or catalyst. It has been well known that the interaction between proteins and microspheres plays important roles in this process. Major interaction involved in the adsorption can be classified as electrostatic, hydrophobic and hydrogen-bonding. Indeed, adsorption of proteins onto microspheres is a complex process and often can involve many dynamic steps, from the initial attachment of the protein on the surface of microspheres to the equilibrium. Also the conformation of proteins probably occurs to a certain degree of deformation or structural change due to the large area of contact. Recently, much interest has been shown in sulfonated microspheres, since sulfonate-group itself is one of components in bio-bodies, as well as is sensitive to the change of pH or ionic strength. Indeed, so far, scanty investigations have been performed in the full range. Also few researches have involved the data on adsorption rate and the maximum amount of protein adsorbed, or the reversibility of the process and conformational change of protein adsorbed as well.In present study, BSA (bovine serum albumin) was chosen as the model protein and sulfonated PMMA [poly(methyl methacrylate)] microspheres as the matrix to investigate the adsorption process.The purpose is to show some information especially the intrinsic information involved by the adsorption process Adsorption of BSA onto sulfonated microspheres (MS) has been investigated as a function of time, protein concentration and pH. The adsorption appears to be a reversible process and the presence of sulfonate groups can play important roles in the adsorption process, so as to increase the amount of protein adsorbed and influences the interaction of BSA molecules. Fig. 1 also shows that the reciprocation between unadsorbed and adsorbed BSA or rearrangement of adsorbed BSA molecules does not produce visible change in the properties of the adsorbed protein. Close to the isoelectric point of BSA (pI 4.7), the amount of protein adsorbed exhibits a maximum. A higher or lower pH results in the significant decrease of the adsorption amount. This is related to the dependence of BSA conformations at different pH conditions.     

Competitive adsorption of sodium dodecyl sulfate and polyethylene oxide at the air/water interface

Geoinspired synthetic chrysotile, which represents an ideal asbestos reference standard, has been utilized to investigate homomolecular exchange of bovine serum albumin (BSA), the major plasma protein, between the adsorbed and dissolved state at the interface between asbestos fibers and biological medium. FTIR spectroscopy has been used to quantify BSA structural modifications due to surface adhesion on chrysotile fibers as a function of the surface coating extent. Circular dichroism spectroscopy has been used to investigate the adsorption/desorption equilibrium through analysis of the BSA structural perturbations after protein desorption from chrysotile surface. Data results show clearly that in the solid state BSA modifications are driven by surface interaction with the substrate, following a bimodal adsorption evidenced by two different binding constants. On the other hand, BSA desorbed in solution is able to rearrange, in the lack of substrate, although keeping irreversible modifications with respect to the native species. The lack of regaining its native structure certainly affects albumin interaction with biological environment. The present investigation on the stoichiometric synthetic geoinspired chrysotile nanocrystals is the first approach toward a deeper attempt to use standard synthetic chrysotile reference samples in mimicking the behavior of asbestos fibers and allows to better understand their interaction with a biological environment.     

Interactions of tannic acid and its derivatives (ellagic and gallic acid) with calf thymus DNA and bovine serum albumin using spectroscopic method

In the present investigation, an attempt has been made to study the interaction of chosen polyphenols (tannic, ellagic and gallic acids) with calf thymus DNA and bovine serum albumin (BSA) employing spectrofluorimetric technique. The fluorescence quenching of DNA-bound ethidium bromide (EB) and BSA-bound 1-anilinonaphthalene-8-sulfonic acid (ANS) by phenolic acids has been examined. As BSA contains two tryptophan residues, the polyphenols influence on protein by measuring the changes in the fluorescence of BSA in the presence of phenolic acids was also evaluated. Our experiments prove that there is a direct interaction between phenols and DNA or BSA. The obtained data suggest that used acids can intercalate to DNA and interact strongly with BSA. The strongest interactions were observed between DNA and ellagic acid and between BSA and tannic acid. The conformational changes were revealed in DNA and BSA after incubation with tested phenolic acids and the extent depended on the phenol structure and the used concentration.     

Binding equilibrium of I- to serum albumin with resonance Rayleigh scattering

The binding equilibrium between l- and human serum albumin (HSA) or bovine serum albumin (BSA) has been studied by means of the resonance Rayleigh scattering (RRS) and equilibrium dialysis. It has been found for the first time that RRS and multiple frequency scattering (MFS) are enhanced as the l- binding to the HSA and BSA, but fluorescence quenches. The equilibrium dialysis results suggest that the binding of l- to HSA and BSA fits a phase-distribution model other than Scsitchard model, and that the order of magnitude of its phase-distribution constant was found to be 104. It is most probable that Cl~ or other anion ions influence the binding of P by changing the ionic strength in the solution. The dialysis at different pH indicates that the binding mechanism is due to the electrostatic forces between the T-and protonated basic amino-acid residues.     

Interactions of adsorbed albumin with underpotentially deposited copper on gold piezoelectrodes

The adsorption of a model protein, bovine serum albumin (BSA), on Au electrodes was investigated using the Cu adatom probe method and Electrochemical Quartz Crystal Nanobalance (EQCN) technique. The adsorption of BSA was confirmed by AFM imaging and has been found to be controlled by kinetics. Using the Cu adatom probe method, we were able to reconstruct the entire BSA adsorption transient Theta(BSA) vs. t. The adsorption rate constant k(1), determined from this transient is k(1)=2.45x10(5) L mol(-1) s(-1). We have found that the bulk Cu(0) deposition process is blocked by BSA adsorption and it decays exponentially with time during BSA adsorption. It ceases completely when a full monolayer of BSA is formed. In contrast to that, the mass associated with Cu-u.p.d. decreases only to ca. 50% of that in the absence of BSA, indicating that Cu adatoms can penetrate (wedge) into the space between the surface Au atoms and the adsorbed BSA molecules. In addition to that, we have found that the degree of penetration of Cu adatoms can be controlled by the applied deposition potential. By selecting a sufficiently cathodic potential, we were able to deposit a full Cu-u.p.d. monolayer, independent of the BSA surface coverage extending from Theta(BSA)=0 to Theta(BSA) approximately 1. The positive shift of Cu(ad) desorption peak potential E(p), observed in the presence of adsorbed BSA, has been interpreted in terms of Frumkin exchange interaction forces between Cu(ad) and BSA(ad), on the basis of our earlier theoretical model, expanded here to include adsorbed species in two monolayers. This expansion is possible owing to the fast rate of Cu adatom penetration in the interfacial region. From the plots of E(p) vs. Theta(BSA), the presence of strong attractive interactions between Cu(ad) and BSA(ad) was deduced. These interactions result in a super-shift of the Cu-u.p.d. desorption peak potential, corresponding to the exchange interaction coefficient g(M,X)<-4, indicating on a possibility of the formation of a stable interface complex.     

牛血清白蛋白与铬天青S作用机理的研究

用三种不同方法相互对照,求出了铬天青S与牛血清白蛋白的结合常数和结合个数,提出了蛋白质等电点前后或不同铬天青S浓度下,两者存在不同的结合模式。利用Forster非辐射能量转移理论确定了铬天青S在牛血清白蛋白上的结合位置,利用铬天青S对BSA的荧光猝灭,对两者的作用机理作了初步探讨。     

丹皮酚及其两种同分异构体与牛血清白蛋白相互作用的热力学研究

在298.15 K下利用等温滴定微量热法研究了丹皮酚(2'-羟基-4'-甲氧基苯乙酮, Pae)及其两种同分异构体(2'-羟 基-5'-甲氧基苯乙酮, Hma; 4'-羟基-3'-甲氧基苯乙酮, Ace)与牛血清白蛋白(BSA)在缓冲溶液(pH≈7.0)中的相互作用. 从药物分子在蛋白质分子上有多种类型相互独立的结合位点的假定出发, 应用Langmuir吸附模型对这三种同分异构体与 BSA 相互作用的量热数据进行了处理. 结果表明, 有两类结合位点存在, 同时计算出了两类结合模式的结合常数、焓变、熵变及吉布斯自由能变等热力学数据. 这两类结合主要以焓驱动为主, 并且在同一类结合位点上, Pae, Hma以及 Ace与BSA结合过程的焓变绝对值依次减小, 这主要是由于客体分子苯环上取代基的相对位置不同而引起热力学数据的差异. 圆二色谱研究表明这三种同分异构体的加入均使BSA的二级结构发生变化, 说明这种生物大分子-药物分子相互作用既包含结合反应也包含小分子诱导BSA分子部分结构改变的过程.