Wettability and surface free energy of bovine serum albumin films

Measurements of the contact angle for water, glycerol, formamide, ethylene glycol, and diiodomethane on polymethyl methacrylate covered by adsorptive bovine serum albumin (BSA) films were made. Adsorption was performed from solutions in the concentration range 0–100 g/L. From the obtained contact angles the Lifshitz-van der Waals components and the values of the electron-acceptor and electrondonor parameters of the acid-based components of the films were calculated for six triplets of liquids. The biggest changes in the BSA film structure occurred under a monolayer coverage (i.e., at BSA concentrations of <2.5 g/L). On the basis of the contact angles of glycerol, ethylene glycol, and formamide it was concluded that the density of BSA polar groups was almost constant. The surface density of the hydrophobic part of the BSA film also seemed constant regardless of the concentration of the solution from which the BSA adsorptive film was created. This conclusion could be drawn from the almost constant contact angle of diiodomethane.     

Multiple response optimization of heat shock process for separation of bovine serum albumin from plasma

Bovine serum albumin produced by heat shock from bovine plasma has been researched for the effects of sodium caprylate concentration [Cap], temperature (T), and pH on yield (Yield%) and purity (BSA%). Response surface methodology and desirability function approaches were applied to optimize its process. The best compromise solution was found with BSA% = 95.0 and Yield% = 28.5 for a [Cap] = 2 mM, T = 67.9°C, and pH = 5. A Monte Carlo simulation showed that it is possible to obtain excellent values for each individual response. However, a techno-economic feasibility study must be carried out to determine which one is the best option.     

同步荧光光谱法研究叶酸与牛血清白蛋白的相互作用

采用紫外光谱法和同步荧光光谱法分析研究了叶酸与牛血清白蛋白的相互作用,由实验结果表明:叶酸(FA)与牛血清白蛋白(BSA)之间具有较强的结合作用而导致荧光猝灭;利用实验数据结合Stern-Volmer方程和热力学方程求出了热力学参数、结合常数及结合位点数。此外,研究了常见金属离子对二者结合有较为显著的影响作用。     

以草甘膦,马拉·毒死蜱为模型研究有机磷农药与牛血清白蛋白的相互作用

利用了荧光发射光谱,同步荧光光谱,紫外吸收光谱进行了检测,研究有机磷农药(草甘膦和马拉硫磷)与牛血清白蛋白的相互作用,实验结果表明了有机磷农药对牛血清白蛋白有着明显的荧光猝灭作用,且方式为静态猝灭(BSA荧光分子与猝灭剂有机磷农药之间通过弱的结合生成复合物,该复合物会使得荧光完全猝灭的现象)为主。通过实验得出有机磷与牛血清白蛋白的结合位点数(n),与结合常数(K0)。     

Adsorption of bovine serum albumin to a polymer brush prepared by atom-transfer radical polymerization in a porous inorganic membrane

Protein adsorption was performed by a polymer brush prepared by atom-transfer radical polymerization (ATRP) to a porous inorganic membrane. The porous inorganic membrane, Shirasu Porous Glass made from silica, was modified with a halogen-containing compound to bind the active species for the polymerization. Glycidyl methacrylate was polymerized from the halogen compound by ATRP for a prescribed time, and subsequently chemically modified. The progression of the chemical modification allowed the membrane to lower the phosphate-buffer flux of the porous membrane due to the attachment of the polymer brush. Bovine serum albumin (BSA), as a model protein, was adsorbed at 12 mg per gram of the membrane in permeating BSA solution through the polymer-brush-attached porous membrane.     

混合模式吸附中辛酸钠和牛血清白蛋白间相互作用

混合模式吸附是一种抗体分离新方法,适量添加辛酸钠,可以减弱血清白蛋白等杂质吸附,提高抗体结合的选择性。本文以MEP HyperCel介质和牛血清白蛋白（BSA）为模型,结合静态吸附平衡和等温滴定量热（ITC）法,考察了辛酸钠浓度、pH、盐和温度等影响,探讨了辛酸钠的作用机制。随辛酸钠浓度增大,BSA和牛血免疫球蛋白的饱和吸附量均呈现先降低后升高的趋势,不过辛酸钠对BSA影响更显著,ITC分析表明辛酸钠与BSA之间存在较强的相互作用,且以疏水作用为主导。添加辛酸钠后,BSA吸附量随pH或温度升高而降低,不同盐具有不同效果,ITC分析表明pH、盐和温度均不同程度影响辛酸钠-BSA相互作用,从而影响MEP HyperCel吸附BSA。结果表明,等温滴定量热分析与宏观吸附现象相一致,可量化分析小分子-蛋白间相互作用,为研究蛋白吸附过程中小分子添加物的作用机制提供了新思路。     

A study of the interaction between fluorescein sodium salt and bovine serum albumin by steady-state fluorescence

The binding of fluorescein sodium salt with three kinds of commercially available bovine serum albumin (BSA) of different grades of purity was investigated at 288, 298 and 313 K by fluorescence and absorption measurements at pH 7.50. The association and dissociation constants K_a and K_d were determined by the quenching of BSA fluorescence in the presence of fluorescein sodium salt. The best results were obtained by fitting raw data by non-linear regression and Lineweaver–Burk equations. The modified Stern–Volmer and Scatchard plots gave less reliable data since the fitting was much more difficult.The agreement of the constants for the three sets of measurements coming from the different BSA was not as good as expected. BSA binding properties differ depending on the different BSA grades of purity. Actually, the binding constants found for the three BSAs used differed in the same set of interactions, even by keeping the experimental conditions constant. These results are a novelty in the field of BSA–ligand binding studies and should be taken into account for future binding studies using BSA. Actually, a large number of aspects should be considered including the grade of purity and the presence of BSA covalent and non-covalent dimers, trimers and oligomers in solution which can affect the goodness of the binding results.     

Water-soluble quaternized mercaptopyridine-substituted zinc-phthalocyanines: Synthesis, photophysical, photochemical and bovine serum albumin binding properties

The synthesis and characterization of the new zinc phthalocyanine derivatives, tetra- (non-peripheral, 5) and octa-(peripheral, 6) substituted with 2-mercaptopyridine and their respective quaternized derivatives (8 and 9) are reported. Photochemical and photophysical properties of the new complexes are compared with those of the previously reported peripherally tetra-substituted complexes 7 and 10. The quaternized compounds exhibit excellent solubility in water, making them potential photosensitizers for use in photodynamic therapy (PDT) of cancer. Spectroscopic, aggregation, photophysical and photochemical properties of these complexes are also investigated and compared. Photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen and photodegradation quantum yield) properties of these phthalocyanine photosensitizers are very important for the assessment of these complexes as PDT agents. In this study, the effects of the position of the substituents and quaternization of the substituents on the photophysical and photochemical parameters of the zinc phthalocyanines are also reported. This study also showed that the water-soluble quaternized zinc phthalocyanines strongly bind to blood plasma proteins such as bovine serum albumin (BSA).     

Electrochemical site marker competitive method for probing the binding site and binding mode between bovine serum albumin and alizarin red S

A novel electrochemical site marker competitive method is proposed for the study of the binding site and the binding mode between bovine serum albumin (BSA) and alizarin red S (ARS). Two known site-selective markers for BSA, bilirubin (BR, for site I) and diazepam (DIA, for site II), were selected to bind to the two potential binding sites of BSA (site I and site II). The resulting BR–BSA or DIA–BSA complex was added into an ARS solution for binding site competition studies. From the current response of ARS after site competition, binding site I of BSA was identified as the binding site of BSA to ARS. Further investigation of the binding events by electrochemistry, fluorescence, and molecular docking techniques revealed that ARS was buried in the hydrophobic cavity of subdomain IIA, mainly through five hydrogen bonds between ARS and residues ARG(193), ARG(255), LYS(220), ARG(197), and ALA(289) of BSA. These efforts will aid in a better understanding of the toxicological action of active components in anthraquinone dyes.     

Silver ferrite and cobalt ferrite dispersed castor oil polyurethane nanocomposites: Quenching studies of bovine serum albumin

The use of renewable resource is a strategic opportunity to meet growing demands of eco-friendly materials. The present study reports the synthesis of castor-oil-based polyurethane (COPU), and its nanocomposites with CoFe₂O₄ and AgFeO₂ via sonication technique. Formation of the nanocomposite was confirmed by IR analysis while UV–visible studies revealed encapsulation of the ferrite particles by COPU. The interaction between COPU, AgFeO₂, CoFe₂O₄, and their nanocomposites with bovine serum albumin (BSA) was also investigated by fluorescence spectroscopy which revealed static quenching of BSA through complex formation. The quenching rate for COPU was determined to be 1.98?×?10⁴?LM^?1 while for pure CoFe₂O₄ and AgFeO₂, it was found to be 3?×?10⁴?LM^?1 and 3.2?×?10⁴?LM^?1, respectively. The interaction of BSA particularly with silver and cobalt ferrite nanoparticles within COPU matrix was found to be promising. It was found that by controlling the loading of ferrite in COPU matrix, desired binding could be achieved.     

光谱法研究十二烷基苯磺酸钠与牛血清白蛋白的相互作用

在pH=7.40的Tris-HCl缓冲溶液体系中,通过荧光光谱法研究了十二烷基苯磺酸钠与牛血清白蛋白的相互作用。运用Stern-Volmer方程和Lineweaver-Burk方程计算了其相互间的猝灭常数、结合常数及结合位点数,在298,308和318K时的表观结合常数分别为0.4108,0.3605和0.048 98 L.μmol-1,其相应的结合位点数分别为1.044,1.041和0.9026,利用热力学参数确定了分子间的作用过程是自发的,作用力主要是静电作用力。同步荧光光谱表明相互作用对蛋白质构象影响不大。     

The interaction between bovine serum albumin and the self-aggregated nanoparticles of cholesterol-modified O-carboxymethyl chitosan

The interaction between bovine serum albumin (BSA) and self-aggregated nanoparticles of cholesterol-modified O-carboxymethyl chitosan (CCMC) with different degrees of substitution (DS) of cholesterol moiety was studied by transmission electron microscopy (TEM), fluorescence quenching method and circular dichroism (CD) measurement. This interaction was started at the disaggregation of CCMC self-aggregated nanoparticles and reached equilibrium after 3-4 h. The apparent quenching constant (K_q) between BSA and CCMC self-aggregated nanoparticles calculated by the modified Stern-Volmer plot increased from 4.14 × 10⁴ to 1.95 × 10⁵ M⁻¹ with DS of cholesterol moiety increasing from 3.2% to 9.8%, whereas the fraction of tryptophan residues in BSA molecule involved in the interaction decreased at the same time. Compared with free BSA, the relative α-helix content of BSA decreased and the unfolding of BSA by a denaturant such as urea was largely suppressed upon interaction with CCMC self-aggregated nanoparticles. DS of cholesterol moiety significantly affected the interaction between BSA and CCMC self-aggregated nanoparticles.     

表面带磺酸基团的聚苯乙烯微球的制备及其对蛋白质的吸附

研究了运用分散聚合法,在乙醇/水混合介质中,制备2-丙烯酰胺基-2-甲基丙磺酸(AMPS)与苯乙烯(St)的共聚微球。运用红外、核磁共振、激光光散射和扫描电子显微镜对功能微球进行表征。阐述了该微球对牛血清蛋白(BSA)的吸附量与吸附时间和pH值的关系。结果表明:功能微球对BSA的吸附先随时间的增长而增大,一段时间后达到平衡吸附。当pH值接近BSA等电点(pI=4.7)时,BSA的吸附量达到最大值。     

Robust SiO2 gate dielectric thin films prepared through plasma-enhanced atomic layer deposition involving di-sopropylamino silane (DIPAS) and oxygen plasma: Application to amorphous oxide thin film transistors

DIPAS (di-isopropylamino silane, H₃Si[N(C₃H₇)₂]) and O₂ plasma were employed, using plasma-enhanced atomic layer deposition (PEALD), to deposit silicon oxide to function as the gate dielectric at low temperature, i.e., below 200 °C. The superior amorphous SiO₂ thin films were deposited through the self-limiting reactions of atomic layer deposition with a deposition rate of 0.135 nm/cycle between 125 and 200 °C. PEALD-based SiO₂ thin layer films were applied to amorphous oxide thin film transistors constructed from amorphous In-Ga-Zn-O (IGZO) oxide layers, which functioned as channel layers in the bottom-gated thin film transistor (TFT) structure, with the aim of fabricating transparent electronics. The SiO₂ gate dielectric exhibited the highest TFT performance through the fabrication of heavily doped n-type Si substrates, with a saturation mobility of 16.42 cm²/V·s, threshold voltage of 2.95 V and large on/off current ratio of 3.69 × 10⁸. Ultimately, the highly doped Si was combined with the ALD-based SiO₂ gate dielectric layers, leading to a saturation mobility of 16.42 cm²/V·s, threshold voltage of 2.95 V, S-slope of 0.1944, and on/off current ratio of 3.69 × 10⁸. Semi-transparent and transparent TFTs were fabricated and provided saturation mobilities of 22.18 and 24.29 cm²/V·s, threshold voltages of 4.18 and 2.17 V, S-slopes of 0.1944 and 0.1945, and on/off current ratios of 9.63 × 10⁸ and 1.03 × 10⁷, respectively.     

Preparation and characterization of nanosized P(NIPAM-MBA) hydrogel particles and adsorption of bovine serum albumin on their surface

Thermosensitive polymer hydrogel particles with size varying from 480 to 620 nm were prepared through precipitation copolymerization of N-isopropylacrylamide with N,N′-methylenebisacrylamide (MBA) in water with ammonium persulfate as the initiator. Only polymer hydrogels without any coagula were obtained when MBA concentration in the monomer mixture was kept between 2.5 and 10.0 wt%; with increased MBA concentration, the monomer conversion was enhanced, the size of the hydrogels was increased, and their shrinking was lessened when heated from 25°C to 40°C. Bovine serum albumin adsorption on the surface of the hydrogels of different MBA content was measured at different pH levels and under different temperatures. The results demonstrated that the adsorption of the protein on the hydrogels could be controlled by adjusting the pH, the temperature of adsorption, and the crosslinking in the hydrogels. The results were interpreted, and the mechanisms of the polymerization were proposed.     

牛血清白蛋白纳米球接枝杨梅单宁的制备以及吸附去除水体中Pb2+的性能

采用去溶剂法和杨梅单宁-戊二醛固化接枝制备得到杨梅单宁（BT）接枝牛血清白蛋白（BSA）纳米球（BSA-BT-NSs）吸附材料，并系统探讨了其在不同吸附条件下对水体中Pb²⁺的吸附去除性能。研究结果表明：50%用量杨梅单宁（基于BSA-NSs量）接枝固化得到的BSA-BT-NSs具有较好的球形结构和良好的分散性。在吸附实验中，Pb²⁺初始浓度为250mg/L、pH 5.0、温度为298K 条件下吸附20min，BSA-BT-NSs（0.4g/L）对Pb²⁺的吸附效果最佳，最大吸附容量为76mg/g，优于多数同类型吸附材料。BSA-BT-NSs对Pb²⁺吸附过程符合Langmuir方程和准二级吸附动力学模型，且吸附后的BSA-BT-NSs经0.1mol/L 硝酸进行解吸取得了92.04％的良好解吸效果，并可再次重复使用。进一步分析其Pb²⁺吸附机理，表明BSA-BT-NSs中的氨基氮原子、羟基和羧基氧原子作为电子供体参与了与Pb²⁺的空轨道发生配位作用。     

Determination of effective diffusion coefficient and interfacial mass transfer coefficient of bovine serum albumin (BSA) adsorption into porous polyethylene membrane by microscope FTIR-mapping study

Here, a new method for simultaneous determination of diffusion coefficient D and interfacial mass transfer coefficient (or convective mass transfer coefficient) k was proposed for bovine serum albumin (BSA) adsorption into porous polymeric membranes. The experimental data for BSA concentration at different membrane depth and different time were determined from FTIR-mapping measurements. Then the diffusion coefficient D and interfacial mass transfer coefficient k were estimated from the calculated dimensionless concentration data at different time and membrane depth by a trial-and-error method based on the diffusion equation initiated in this paper. The diffusion coefficient D and interfacial mass transfer coefficient k evaluated in this manner are respectively: and . The theoretical concentration values calculated from the determined parameters were compared with experimental reading from FTIR mappings, which showed a good agreement between them, especially for the case of a relatively long-time adsorption.     

Continuous production of biodiesel from cottonseed oil and methanol using a column reactor packed with calcined sodium silicate base catalyst☆

Sodium silicate and that calcined at 400 °C for 2 h were used to catalyze the transesterification of cottonseed oil with methanol. Calcined sodium silicate(CSS) catalyst exhibited much higher catalytic activity and stability. A maximum biodiesel yield of 98.9% was achieved at methanol/oil mole ratio of 12:1, reaction temperature65 °C, reaction time 3.0 h, and CSS/oil mass ratio of 2 wt%. After 7 consecutive reactions without any treatment,biodiesel yield reduced to 82.5%. Considering technological and economic feasibility, CSS base catalyst supported on θ rings was prepared for continuous transesterification. The maximum yield was 99.1% under optimum conditions(reaction temperature 55 °C, methanol velocity 1 ml·min-1, oil velocity 3 ml·min-1, and 5 tower sections). These results indicate that this new continuous biodiesel production process and apparatus present a great potential for industrial application in biodiesel.     

Ni0.5Zn0.5Fe2O4 nanoparticles and their magnetic properties and adsorption of bovine serum albumin

Ni_0.5Zn_0.5Fe₂O₄ nanoparticles were synthesized by the facile citrate-gel process and the preliminary measurement for adsorption of bovine serum albumin (BSA) protein on these nanoparticles was carried out. The gel precursor and resultant nanoparticles were characterized by TG-DSC, FTIR, XRD, TEM and VSM techniques and the BSA adsorption on the nanoparticles was analyzed by UV spectrophotometer at room temperature. The results show that the single phase of spinel Ni_0.5Zn_0.5Fe₂O₄ is formed at 400 °C. With increasing calcination temperature from 400 to 700 °C, the average grain size increases from about 14 to 45 nm and consequently, the specific saturation magnetization of Ni_0.5Zn_0.5Fe₂O₄ nanoparticles increases from about 46 to 68 Am²/kg. The coercivity initially increases and then decreases with increasing calcination temperature, with a maximum value 9.2 kA/m at 500 °C. The as-prepared Ni_0.5Zn_0.5Fe₂O₄ nanoparticles exhibit a good adsorbing ability for BSA and the optimized adsorption is achieved for the Ni_0.5Zn_0.5Fe₂O₄ nanoparticles calcined at 500 °C with grain size about 24 nm.     

Electrochemical cleaning of microporous metallic filters fouled with bovine serum albumin and phosphate under low cross-flow velocities

A three-electrode electrochemical cell has been designed to test the cleaning efficiency of applying potentials or currents to 0.2 m pore size silver membranes fouled with bovine serum albumin and phosphate under low cross-flow velocities. It was found that with the improved electrochemical efficiency of the three-electrode design (compared to two-electrode cells) only relatively small current densities (about –40 A cm^–2) needed to be applied in order to charge the membranes sufficiently to cause the reduction of water. The best results for electrochemically cleaning fouled membranes were obtained when negative currents were applied to membranes in a moderate strength acid environment. It was found that the interfacial pH changes associated with the reduction of water were important in cleaning the membranes in addition to the agitation action of bubbles of hydrogen gas.