间苯二酚与牛血清白蛋白的作用机理

采用荧光和紫外光谱法研究了间苯二酚与牛血清白蛋白(BSA)的相互作用。间苯二酚使BSA的构象发生改变,α-螺旋含量减小。同步荧光光谱发现间苯二酚使BSA色氨酸残基的疏水性降低,酪氨酸残基的疏水性增强。荧光光谱表明猝灭机理为静态猝灭,计算了复合物的结合常数,通过热力学参数得出间苯二酚与BSA之间的作用力主要是静电作用力。     

邻苯二酚与牛血清白蛋白的相互作用

采用荧光和紫外光谱法研究了邻苯二酚同牛血清白蛋白(BSA)的作用.邻苯二酚对BSA内源荧光猝灭机理为静态猝灭,两者之间生成了不发荧光的复合物.根据双对数方程计算了复合物的结合常数KA和结合位点数n.确定邻苯二酚与BSA只有一个结合位点(可能位于Site I).通过热力学参数得出邻苯二酚与BSA之间主要作用力是疏水作用.同步荧光的结果表明邻苯二酚改变了BSA的分子构象,使色氨酸残基的极性增加,酪氨酸残基的疏水性增强.     

The effects of ligand chain length, salt concentration and temperature on the adsorption of bovine serum albumin onto polypropyleneglycol-Sepharose

The interaction thermodynamics associated with bovine serum albumin adsorption on polypropylene glycol (n=3)-Sepharose CL-6B and polypropylene glycol (n=7)-Sepharose CL-6B, using ammonium sulfate as the modulator was studied. Analysis of data under linear conditions was accomplished with the stoichiometric displacement retention model, preferential interaction approach and van't Hoff plots applied to HIC systems. Preferential interaction analysis indicated a strong entropic driving force under linear conditions, due to the release of a large amount of solvent on adsorption. In contrast, flow microcalorimetry under overloaded conditions showed that the adsorption of bovine serum albumin may be entropically or enthalpically driven. It is postulated that adsorption in the nonlinear region is influenced by the degree of water release, protein-protein interactions on the surface, reorientation of ligand, and conformational changes in the protein.     

Interaction of polyethyleneimine-functionalized ZnO nanoparticles with bovine serum albumin

In biological fluids, nanoparticles are always surrounded by proteins. As the protein is adsorbed on the surface, the extent of adsorption and the effect on the protein conformation and stability are dependent on the chemical nature, shape, and size of the nanoparticle (NP). We have carried out a detailed investigation on the interaction of bovine serum albumin (BSA) with polyethyleneimine-functionalized ZnO nanoparticles (ZnO-PEI). ZnO-PEI was synthesized using a wet chemical method with a core size of ~3-7 nm (from transmission electron microscopy). The interaction of BSA with ZnO-PEI was examined using a combination of calorimetric, spectroscopic, and computational techniques. The binding was studied by ITC (isothermal titration calorimetry), and the result revealed that the complexation is enthalpy-driven, indicating the possible involvement of electrostatic interaction. To investigate the nature of the interaction and the location of the binding site, a detailed domain-wise surface electrostatic potential calculation was performed using adaptive Poisson-Boltzmann software (APBS). The result shows that the protein surface can bind the nanoparticle. On binding ZnO-PEI, the protein gets destabilized to some extent, as displayed by CD (circular dichroism) and FTIR (Fourier transform infrared) spectroscopy. Chemical and thermal denaturation of BSA, when carried out in the presence of ZnO-PEI, also indicated a small perturbation in the protein structure. A comparison of the enthalpy and entropy components of binding with those derived for the interaction of BSA with ZnO nanoparticles explains the effect of hydrophilic cationic species attached on the NP surface. The effect of the NP surface modification on the structure and stability of BSA would find useful applications in nanobiotechnology.     

Interaction of magnolol with bovine serum albumin: a fluorescence-quenching study

The interaction of magnolol with bovine serum albumin(BSA) was studied using fluorescence spectroscopy under physiological conditions. The binding constants, K, and the ratio of quantum yields of protein fluorescence for complex and free protein, f, at 298 K, 304 K, and 310 K were obtained; the values were 6.799×10⁵ L mol^–1, 5.541×10⁵ L mol^–1, and 4.344×10⁵ L mol^–1 and 0.17, 0.30, and 0.34, respectively. The standard enthalpy change (H°) and the standard entropy change (S°) were calculated to be –28.53 kJ mol^–1 and 15.88 J mol^–1 K^–1, which indicated that hydrophobic forces played major role in the interaction of magnolol and BSA. The binding average distance between magnolol and BSA (4.32 nm) was obtained on the basis of the theory of Förster energy transfer.     

Interaction of aspirin and vitamin C with bovine serum albumin

Vitamin C (L-ascorbic acid) has a major biological role as a natural antioxidant. Aspirin belongs to the nonsteroidal anti-inflammatory drugs and functions as an antioxidant via its ability to scavenge-OH radicals. Bovine serum albumin (BSA) is the major soluble protein constituent of the circulatory system and has many physiological functions including transport of a variety of compounds. In this report, the competitive binding of vitamin C and aspirin to bovine serum albumin has been studied using constant protein concentration and various drug concentrations at pH 7.2. FTIR and UV-Vis spectroscopic methods were used to analyze vitamin C and aspirin binding modes, the binding constants and the effects of drug complexation on BSA stability and conformation. Spectroscopic evidence showed that vitamin C and aspirin bind BSA via hydrophilic interactions (polypeptide and amine polar groups) with overall binding constants of K(vitamin C-BSA)=1.57×10(4)M(-1) and K(aspirin-BSA)=1.15×10(4)M(-1); assuming that there is one drug molecule per protein. The BSA secondary structure was altered with major decrease of α-helix from 64% (free protein) to 57% (BSA-vitamin C) and 54% (BSA-aspirin) and β-sheet from 15% (free protein) to 6-7% upon drug complexation, inducing a partial protein destabilization.     

Interaction of bovine serum albumin with chrysotile: spectroscopic and morphological studies

The biodurability of chrysotile fibers, which is related to their cytotoxicity and mutagenic responses, is strongly affected by the surface chemical adsorption of biological molecules. Natural chrysotile is a heterogeneous material in both structure and composition. The availability of synthetic stoichiometric chrysotile of constant structure and uniform morphology has allowed us to investigate its interaction with bovine serum albumin (BSA). By using transmission electron microscopy (TEM) and atomic force microscopy (AFM), we have obtained the first morphological evidence of albumin adsorption onto chrysotile nanocrystals. FTIR spectroscopy was used to quantify modifications of BSA secondary structure that were induced by the surface interaction. The protein transition to beta-turns allows a stronger interaction between the protein hydrophilic side-chains and the charged asbestos surface, which is consistent with hydrogen bonds involving the superficial OH groups. Synthetic stoichiometric chrysotile nanocrystals were shown to be an ideal reference standard with which to study the interaction of asbestos fibers with biological systems, in order to elucidate the chemical mechanisms of asbestos toxicity.     

Interaction of pyrene-end-capped poly(ethylene oxide) with bovine serum albumin and human serum albumin in aqueous buffer medium: a fluorometric study

The photophysical behavior of a hydrophobically tailored water-soluble polymer, pyrene-end-capped poly(ethylene oxide) (PYPY), has been studied in aqueous buffered bovine serum albumin (BSA) and human serum albumin (HSA) media. In buffered aqueous solution the polymer shows dual emission corresponding to the monomer and the excimer of pyrene moiety. The relative intensity of the monomer to the excimer emission shows interesting variation with the addition of BSA and HSA and is indicative of significant interaction of these albumin proteins with the polymer. The binding interaction has been shown to have a prominent role on the steady state fluorescence anisotropy of the two emission bands. Attempt has been made to determine the micropolarities of the protein microenvironments from a comparison of the variation of the monomer to excimer relative fluorescence intensities of the probe in water–dioxane mixtures with varying composition.     

Binding of oxovanadium(V) anion to bovine serum albumin,human serum albumin and bovine pancreatic trypsin

The binding of vanadium(V) to bovine serum albumin (BSA), human serum albumin (HSA), and bovine pancreatic trypsin in the absence and presence of urea has been studied at different pH values and temperatures by spectrophotometric and equilibrium dialysis methods. The binding data were found to be pH and temperature dependent. The binding data at pH 5.57, studied by the absorbance method, were found approximately identical with those obtained from the equilibrium dialysis method at this pH. The enthalpy change at pH 5.57 for vanadium(V)-protein was −368.4 cal Mole⁻¹ for BSA, −328.8 cal Mole⁻¹ for HSA and −1372 cal Mole⁻¹ for trypsin respectively. The association constants and the number of binding sites were calculated from Scatchard plots and found to be at maximum at lower pH and at lower temperature. The free energy of the combining sites was lowest at higher pH and highest at low pH. Therefore, a lower temperature and a lower pH offered more sites in the protein molecule for interaction with vanadium(V) ions. Statistical effects seem to be more significant at lower vanadium(V) ion concentrations, and electrostatic effects more significant at higher concentrations.     

荧光光谱法研究4-硝基苯胺与牛血清白蛋白的相互作用

在模拟动物生理条件下利用荧光光谱法从分子水平上研究了4-硝基苯胺同牛血清白蛋白(BSA)的相互作用.4-硝基苯胺对BSA的荧光有较强猝灭作用.用Stern-Volmer方程和双对数方程分别处理实验数据发现BSA与4-硝基苯胺发生反应生成了新的复合物,猝灭机理以静态碎灭为主.根据双对数方程求出了不同温度下反应时复合物的形...     

Interaction of epicatechin with bovine serum albumin using fluorescence quenching combined with chemometrics

The interaction between BSA and epicatechin was studied using fluorescence quenching titrations combined with trilinear decomposition method and excitation-emission matrix(EEM)fluorescence.The resolved spectra were highly similar with the actual ones which indicated that the resolved results were reliable.The relevant parameters of the binding process were obtained by quantifying each substance in the complicated mixtures in situ.The quenching was static quenching,epicatechin had a weak interaction with BSA and the binding site was one.The total concentration and the free concentration of quenchers had different effect on the system.The results demonstrated that the method exploited in this article is a useful tool to investigate complicated interactions,avoiding complicated pretreatment and simplify experimental procedure.     

Interaction of 7-hydroxyflavone with human serum albumin: a spectroscopic study

Numerous recent investigations have revealed that various synthetic as well as therapeutically active natural flavonoids possess novel luminescence properties that can serve as highly sensitive monitors for exploring their interactions with relevant physiological targets. Here we report a detailed study on the interactions of the model flavone, 7-hydroxyflavone (7HF) with the plasma protein human serum albumin (HSA), employing electronic absorption, fluorescence (steady state and time resolved) and induced circular dichroism (ICD) spectroscopy. The spectral data indicate that in the protein matrix, the neutral 7HF molecules are predominantly transformed to a conjugate anion (7HFA) by a proton abstraction in the ground state. The protein (HSA) environment induces dramatic enhancements in the fluorescence emission intensity, anisotropy (r) and lifetime (tau) values, as well as pronounced changes in the fluorescence excitation and emission profiles of the fluorophore. Moreover, evidence for efficient F?rster type resonance energy transfer (FRET, from tryptophan to 7HFA) is presented, from which we infer that the binding site of 7HF in HSA is proximal (estimated distance, R=23.6A) to the unique tryptophan - 214 residue present in the inter-domain (between IIA and IIIA domains) loop region of the protein. The binding constant (K=9.44x10(4)M(-1)) and the Gibbs free energy change (DeltaG=-28.33kJ/mol) for 7HFA-HSA interaction have been estimated from the emission data. Finally, the near-UV circular dichroism (CD) studies show that the electronic transitions of 7HF are strongly perturbed on binding to the chiral host (HSA), leading to the appearance of ICD bands. Implications of these results are discussed.     

头孢噻肟-Cu(Ⅱ)-牛血清白蛋白相互作用的荧光光谱法研究

用荧光光谱法研究了生理酸度条件下,头孢噻肟对牛血清白蛋白,Cu(Ⅱ)对牛血清白蛋白以及Cu(Ⅱ)对头孢噻肟和牛血清白蛋白荧光光谱特性的影响。结果表明:Cu(Ⅱ)和头孢噻肟均可使牛血清白蛋白的荧光强度发生静态猝灭,并且在Cu(Ⅱ)存在下,头孢噻肟对牛血清白蛋白的荧光猝灭作用显著增强。根据荧光猝灭双倒数图计算头孢噻肟和牛血清白蛋白的结合常数为3.11×104L/mol,结合位点数为1.03;二元配合物Cu(Ⅱ)与牛血清白蛋白之间的结合常数为1.13×103L/mol,结合位点数为0.74。     

Comparative DSC study of human and bovine serum albumin

The thermal denaturation process of bovine and human both fatty acid containing and fatty acid free albumins in aqueous solution was studied by use of differential scanning calorimetry. Human serum albumins were found to be more stable than their bovine counterparts. Fatty acid free albumins were characterized as generally less stable, more susceptible to aggregation, their unfolding endothermic transition was less cooperative and with the smaller degree of reversibility. Deconvolution analysis with using a non-two-state model with two component transitions showed essential differences in the thermodynamic parameters between all studied albumins, particularly regarding the high-temperature component transition.     

Interaction of chlorin p6 with bovine serum albumin and photodynamic oxidation of protein

The binding of chlorin p6, a photosensitizer having basic tetrapyrrole structure, to bovine serum albumin (BSA) and oxidation of the protein following photodynamic treatment is studied. The Stern-Volmer plot indicates that binding of chlorin p6 to BSA was of single class. Binding parameters, binding association constant and number of binding sites, were found to be 1.62+/-0.27 x 10(5)M(-1) and 1.086+/-.019, respectively. Photodynamic oxidation of protein was studied by (i) loss of intrinsic fluorescence of protein, (ii) protein carbonyl formation, (iii) protein hydroperoxide (iv) formation of TCA soluble amino groups and (v) SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Intrinsic protein fluorescence was observed to decrease almost linearly as a function of irradiation time at a fixed concentration of chlorin p6 and with increasing concentration of chlorin p6 at fixed time of irradiation. Protein carbonyl and hydroperoxide formation was found to increase with increasing photodynamic treatment. No significant increase in 5% TCA soluble amino groups was observed. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) reveals that photodynamic treatment of BSA in presence of chlorin p6, rose bengal and riboflavin causes non-specific fragmentation of protein. Photodynamic carbonyl formation by chlorin p6 was not inhibited by sodium formate (100 mM) or mannitol (25 mM) but was significantly inhibited by sodium azide (2 mM). Protein carbonyl formation increased almost 90% when H2O was replaced by D2O. The results show that chlorin p6 induced photodynamic oxidation of BSA was mainly mediated by singlet oxygen.     

Interaction of colloidal AgTiO2 nanoparticles with bovine serum albumin

The interaction between colloidal AgTiO₂ nanoparticles and bovine serum albumin (BSA) was studied by using absorption, steady state, time resolved and synchronous fluorescence spectroscopy measurements. Absorption spectroscopy proved the formation of a ground state BSA?AgTiO₂ complex. Upon excitation of BSA, colloidal AgTiO₂ nanoparticles effectively quenched the intrinsic fluorescence of BSA. The number of binding sites (n = 1.06) and apparent binding constant (K = 3.71 × 10⁵ M⁻¹) were calculated by the fluorescence quenching method. A static mechanism and conformational changes of BSA were observed.     

Interaction between Janus Green B and bovine serum albumin:Electrochemistry and spectroscopy studies

In this study,voltammetric and spectroscopic investigation of the interaction between Janus Green B(JGB) and bovine serum albumin(BSA) was reported.The interaction was observed at Britton-Robinson buffer(pH 7.0).When JGB was added to solution containing BSA,the peak currents of BSA decrease with the increasing of JGB concentrations which is due to the interaction of JGB and BSA.The binding constant of JGB with BSA was obtained by voltammetric data.Also,this interaction was supported by means of UV-vis spectroscopic measurements.The UV-vis absorption spectra of JGB in the presence of BSA decrease with the increasing of BSA concentrations.     

Interaction of tetrandrine with human serum albumin: a fluorescence quenching study.

The interaction of tetrandrine with human serum albumin (HSA) was studied by measuring fluorescence quenching spectra, synchronous fluorescence spectra and ultra-violet spectra. The fluorescence quenching spectra of HSA in the presence of tetrandrine showed that tetrandrine quenched the fluorescence of HSA. The quenching constants of tetrandrine on HSA were determined using the Stern-Volmer equation. Static quenching and non-radiation energy transfer were the two main reasons leading to the fluorescence quenching of HSA by tetrandrine. According to the F?rster theory of non-radiation energy transfer, the binding distances (r) and the binding constants (K(A)) were obtained. The thermodynamic parameters obtained in this study revealed that the interaction between tetrandrine and HSA was mainly driven by a hydrophobic force. The conformational changes of HSA were investigated by synchronous spectrum studies.