PeakMaster软件计算毛细管电泳缓冲液pH和离子强度

在介绍PeakMaster软件基本功能的基础上，重点对其在毛细管电泳背景电解质pH和离子强度计算方面的应用进行了详细介绍，并将PeakMaster计算出的毛细管电泳常用缓冲溶液的pH和离子强度值与文献报道值进行了比较。     

用于计算机模拟的ab initio N2-H2O势

用6-31G^*^*基组对N2-H2O体系作了量子化学ab initio计算研究。采用模拟褪火(Simulated anneal)算法将所得的计算结果用于拟合一个适用于计算机模拟的解析势能函数。函数的形式为10-6的Lennard-Jones势加指数项校正。鉴于非极性溶质的排斥能对第一水合层的形成起着重要作用, 在拟合过程中对势能的排斥部分和吸引部分作了等权考虑。     

用于计算机模拟的ab initio N2-H2O势

用6-31G基组对N_2-H_2O体系作了量子化学ab initio计算研究.采用模拟褪火(Simulated anneal)算法将所得的计算结果用于拟合一个适用于计算机模拟的解析势能函数.函数的形式为10-6的Lennard-Jones势加指数项校正.鉴于非极性溶质的排斥能对第一水合层的形成起着重要作用,在拟合过程中对势能的排斥部分和吸引部分作了等权考虑.     

水及有机溶剂中离子溶剂化焓的理论计算

离子溶剂化热力学的理论研究是一项令人感兴趣的工作.在Born理论的基础上人们先后提出了多种较详细的计算离子溶剂化热力学量的模型或公式,并对离子在不同溶剂中的溶剂化自由能进行了理论计算.本文从离子-溶剂间的相互作用力出发,分别考虑了离子溶剂化过程中造腔作用、静电吸引、静电排斥及非静电相互作用对离子溶剂化焓的贡献,得到了一个具有一定意义的、计算离子溶剂化焓的理论公式。     

荧光素钠互变异构体的表面增强共振喇曼散射光谱

本文报导了不同pH值下荧光素钠吸附于银岛膜的表面增强共振喇曼散射(SERRS)光谱。由于在不同pH值的溶液中荧光素钠具有不同的离子构型, 其SERRS光谱也有所不同, 其差异主要表现在谱线强度的变化而不是频率变化。谱线强度随pH值的变化形式可分为两种类型, 这与其相对应的振动模的性质有关。利用“四级能模型”和共振喇曼理论对实验结果进行了分析。     

三辛基甲基氯化铵萃取色氨酸的影响因素

研究了水相离子强度、无机盐类型、萃取剂浓度、水相初始 pH0 值对色氨酸在三辛基甲基氯化铵(TOMAC) /正辛烷体系中分配行为的影响。实验结果表明 ,色氨酸的分配系数随着离子强度的增加而降低 ,但是当离子强度增大到一定程度时变化趋于平缓 ;分析了由于离子强度的影响而使实际过程的分配系数与理想过程分配系数不同的原因 ,得出了离子强度与活度系数的关系式 ;在萃取过程中增加有机相萃取剂浓度可提高两相间的分配系数DA;提高水相 pH0 值能提高色氨酸在两相间的分配系数DA,但当 pH0 >11时 ,对分配系数的影响很小 ;阳离子均为Na+ 情况下 ,DCl- >DBr- ;阴离子均为Cl-时 ,DNa+ >DK+ 。     

壳聚糖-丝心蛋白合金膜的研究(Ⅱ)──半互穿聚合物网络型膜对pH和离子的敏感性

研究了壳聚糖-丝心蛋白半互穿聚合物网络型膜对pH值和离子的敏感性,发现该膜在pH<3.3时溶胀度剧烈增加;在pH=2时,是否出现溶胀极大值与膜组分的含量及交联剂的含量有关;膜在不同pH值溶液中可交替溶胀和收缩,且这种溶胀-收缩行为重复可逆。同时,该膜在不同离子溶液中的溶胀度亦不同;在相同离子强度的溶液中,此膜在3价离子中的溶胀度最大。     

电子计算机在分析化学上的应用——掩蔽剂存在下微溶化合物沉淀pH值的计算

本文从理论上计算掩蔽剂存在下,微溶化合物沉淀pH值的通用方程;运用BASLC语言将此通式编制成计算机程序,并使用该程序对几种类型沉淀的pH值改变以及不同离子间获得定量分离的pH范围进行了计算,结果均令人满意。     

弱电解质解离热力学研究 Ⅰ.对硝基苯酚-NaCl-水体系

本文在298.15±0.2K 测定了九个恒定离子强度不同 pH 值缓冲溶液中对硝基苯酚有等吸收点的紫外谱图.在恒定总离子强度为 I=0.1-2.0mol/kg 条件下,利用谱图中的光密度数据和测定的 pH 值,根据扩展的 Debye-Hückel 公式外推得到 pK°=7.246.K°为对硝基苯酚的热力学解离常数.本文又提出了用多项式拟合法确定 pK°,其值为7.308.两者在实验误差范围内一致.     

Cr~(3 )的水解聚合作用的研究Ⅰ.

本文报道对水合Cr(III)离子的聚合过程及其生成多核化合物进行研究的结果.配制几组硝酸铬溶液,使其中Cr(III)离子浓度和pH值不同而离子强度相同.一般约需一个月始达平衡,然后测定其pH值.数据按“根 节”理论处理,结果表明溶液中生成一系列通式为Cr[Cr(OH)_2]_n~((3 n) )的络合物,式中n=1,2和3.用曲线拟合法、投影带法、曲线外推法等三种方法计算,所得平衡常数K_n极为一致.     

用解析Ross变分微扰理论研究蛋白质盐溶液的渗透压

采用软球三Yukawa势代替文献中的硬核双Yukawa势描述带电蛋白质分子之间的色散吸引、色散排斥和屏蔽静电排斥作用, 采用Ross变分微扰理论推导出解析状态方程(EOS), 克服了文献中常用的平均球近似对多Yukawa势存在的困难. 应用新理论研究了牛血清蛋白(BSA)-NaCl水溶液在不同pH值、不同浓度下的渗透压. 结果表明该理论独立参数的个数仅比林阳政等人最近提出的理论多一个, 而精确度有很大提高. 分析表明, 对于分子量大的蛋白质溶液体系采用新的软球理论比硬球理论会有明显的改进.     

Protein—Protein Interactions in Aqueous Ammonium Sulfate Solutions. Lysozyme and Bovine Serum Albumin (BSA)

Osmotic pressures have been measured to determine lysozyme—lysozyme,BSA—BSA, and lysosyme—BSA interactions for protein concentrations to 100 g-L^–1in an aqueous solution of ammonium sulfate at ambient temperature, as a functionof ionic strength and pH. Osmotic second virial coefficients for lysozyme, forBSA, and for a mixture of BSA and lysozyme were calculated from theosmotic-pressure data for protein concentrations to 40 g-L^–1. The osmotic second virialcoefficient of lysozyme is slightly negative and becomes more negative withrising ionic strength and pH. The osmotic second virial coefficient for BSA isslightly positive, increasing with ionic strength and pH. The osmotic second virialcross coefficient of the mixture lies between the coefficients for lysozyme andBSA, indicating that the attractive forces for a lysozyme—BSA pair areintermediate between those for the lysozyme—lysozyme and BSA—BSA pairs. For proteinconcentrations less than 100 g-L^–1, experimental osmotic-pressure data comparefavorably with results from an adhesive hard-sphere model, which has previouslybeen shown to fit osmotic compressibilities of lysozyme solutions.     

pH对氟喹诺酮药物与BSA之间相互作用影响的研究

采用毛细管区带电泳法,通过测定在不同pH值、不同牛血清白蛋白(BSA)浓度缓冲溶液的条件下药物迁移时间的变化,并分别计算出了pH为6.8、7.4和8.0时培氟沙星、左氧氟沙星、氧氟沙星、环丙沙星等四种氟喹诺酮类药物与BSA相互作用的结合常数.结果表明:pH对结合常数有较大影响,四种药物分子结合常数的最大值均出现在pH=6.8时,并随着pH的增大,结合常数值明显下降.根据实验结果,还对四种氟喹诺酮类药物与BSA之间相互作用的类型、作用位置进行了分析探讨.研究结果对于进一步阐明药用机理并迅速开发出更高效的广谱抗菌药物具有较强的理论意义.     

Correlation and Prediction of Osmotic Pressures for Aqueous Bovine Serum Albumin-NaCl Solutions Based on Two Yukawa Potentials

A new equation of state is proposed to correlate and predict the osmotic pressure data for aqueous bovine serum albumin (BSA) solutions with different NaCl concentrations and pH values with only one adjustable parameter. The Carnahan-Starling equation represents the contribution of the hard sphere repulsion to the osmotic pressure. The attractive dispersion and double-layer repulsion interactions are represented by two Yukawa potentials, respectively. The equation of state of Duh and Mier-Y-Teran for one Yukawa potential is expanded to two Yukawa potentials to describe the nonidealities of the charged BSA-aqueous NaCl solution, instead of the classical DLVO theory. The average relative deviation of correlation of the osmotic pressure in 0.15 M NaCl solution is 18%. The average relative deviation of prediction in 1-5 M NaCl solutions is 20.33%. A comparison with other models and the limitations of our model are discussed. Copyright 2001 Academic Press.     

A modified box model including charge regulation for protein adsorption in a spherical polyelectrolyte brush

Recent experiments showed significant adsorption of bovine serum albumin (BSA) in spherical polyelectrolyte brushes (SPB) consisting of polyacrylic acid, even for pH values above the isoelectric point of the protein, when both protein and polyion are negatively charged. To describe these experimental findings theoretically, we have constructed a spherical box model for an annealed brush consisting of a weak polyelectrolyte that includes the adsorption of BSA. At equilibrium the chemical potential of BSA in solution equals that at each location in the brush, while the net force on the polyions (including osmotic, stretching, and excluded volume terms) is zero at each location. Protein adsorption is predicted above the isoelectric point and--in agreement with experimental data--is a strong function of ionic strength and pH. Adsorption of protein in the brush is possible because the pH in the brush is below the isoelectric point and protein reverses its charge from negative to positive when it adsorbs.     

Selective and sequential adsorption of bovine serum albumin and lysozyme from a binary mixture on nanosized magnetic particles

Magnetic particles about 10 nm in size were prepared by chemical precipitation under nitrogen and used for the selective and sequential adsorption of bovine serum albumin (BSA) (pI = 4.7) and lysozyme (LSZ) (pI = 1.1) under different conditions, such as pH and initial protein concentration. The separation ratio of BSA over LSZ at pH 4.6 is about 5, which is about 1.5 times the separation ratio of LSZ over BSA at pH 11.0. Only 10% of the preadsorbed BSA could be displaced by the sequential adsorption of LSZ at pH 11.0. On the other hand, 60% of the preadsorbed LSZ was desorbed due to the sequential adsorption of BSA at pH 4.6. Over 50% desorption of BSA or LSZ could be achieved either by 0.5 M Na(2)HPO(4) or 0.5 M NaH(2)PO(4) after 2 h. Over 80% of the enzymatic activity of LSZ was preserved when it was desorbed from magnetic particles.     

Interfacial behavior of N-nitrosodiethylamine/bovine serum albumin complexes at the air-water and the chloroform-water interfaces by axisymmetric drop tensiometry

Interfacial properties of N-nitrosodiethylamine/bovine serum albumin (NDA/BSA) complexes were investigated at the air-water interface. The interfacial behavior at the chloroform-water interface of the interaction product of phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), dissolved in the chloroform phase, and NDA/BSA complex, in the aqueous phase, were also analyzed by using a drop tensiometer. The secondary structure changes of BSA with different NDA concentrations were monitored by circular dichroism spectroscopy at different pH and the NDA/BSA interaction was probed by fluorescence spectroscopy. Different NDA/BSA mixtures were prepared from 0, 7.5 x 10(-5), 2.2 x 10(-4), 3.7 x 10(-4), 5 x 10(-4), 1.6 x 10(-3), and 3.1 x 10(-3) M NDA solutions in order to afford 0, 300/1, 900/1, 1 500/1, 2 000/1, 6 000/1, and 12 500/1 NDA/BSA molar ratios, respectively, in the aqueous solutions. Increments of BSA alpha-helix contents were obtained up to the 2 000/1 NDA/BSA molar ratio, but at ratios beyond this value, the alpha-helix content practically disappeared. These BSA structure changes produced an increment of the surface pressure at the air-water interface, as the alpha-helix content increased with the concentration of NDA. On the contrary, when alpha-helix content decreased, the surface pressure also appeared lower than the one obtained with pure BSA solutions. The interaction of DPPC with NDA/BSA molecules at the chloroform-water interface produced also a small, but measurable, pressure increment with the addition of NDA molecules. Dynamic light scattering measurements of the molecular sizes of NDA/BSA complex at pH 4.6, 7.1, and 8.4 indicated that the size of extended BSA molecules at pH 4.6 increased in a greater proportion with the increment in NDA concentration than at the other studied pH values. Diffusion coefficients calculated from dynamic surface tension values, using a short-term solution of the general adsorption model of Ward and Tordai, also showed differences with pH and the NDA concentration. Both, the storage and loss dilatational elastic modulus were obtained at the air-water and at the chloroform-water interfaces. The interaction of NDA/BSA with DPPC at the chloroform-water produced a less rigid monolayer than the one obtained with pure DPPC (1 x 10(-5) M), indicating a significant penetration of NDA/BSA molecules at the interface. At short times and pH 4.6, the values of the storage elastic modulus were larger and more sensible to the NDA addition than the ones at pH 7.1 and 8.4, probably due to a gel-like network formation at the air-water interface.     

放射标记法研究壳聚糖与牛血清白蛋白的自组装超薄膜

基片在两种带有相反电荷的聚电解质溶液中交替吸附 ,其表面形成致密有序的超薄膜的自组装 (ＥＳＡ ｅｌｅｃｔｒｏｓｔａｔｉｃｓｅｌｆ ａｓｓｅｍｂｌｙ)技术是由Ｄｅｃｈｅｒ及其合作者在 1 991年提出[1] ,由于简单易行 ,从一出现就受到了广大研究者的极大兴趣[2～ 4 ] .对生物材料来说 ,这无疑是一项非常重要且方便的表面改性手段 .因为生物材料在生物体内种植时 ,是否会被机体视为异物 ,关键在于机体与材料表面的相互作用 ,而与材料的本体性质基本无关[5] .因此利用这种技术 ,可对生物材料 ,特别是对那些生物相容性不好的材料表面进行…     

Effect of pH on the interaction of vitamin B12 with bovine serum albumin by spectroscopic approaches

The interaction mechanism between vitamin B12 (B12, cyanocobalamin) and bovine serum albumin (BSA) has been investigated by fluorescence, synchronous fluorescence, ultraviolet-vis (UV) absorbance, and three-dimensional fluorescence. The intrinsic fluorescence of BSA was strongly quenched by the addition of B12 in different pH buffer solutions (pH 2.5, 3.5, 5.0, 7.4, and 9.0) and spectroscopic observations are mainly rationalized in terms of a static quenching process at lower concentration of B12 (C(B12)/C(BSA)<5) and a combined quenching process at higher concentration of B12 (C(B12)/C(BSA)>5). The structural characteristics of B12 and BSA were probed, and their binding affinities were determined under different pH conditions. The results indicated that the binding abilities of B12 to BSA in the acidic and basic pH regions (pH 2.5, 3.5, 5.0, and 9.0) were lower than that at simulating physiological condition (pH 7.4). In addition, the efficiency of energy transfer from tryptophan fluorescence to B12 was found to depend on the binding distance r between the donor and acceptor calculated using F?rster's theory. The effect of B12 on the conformation of BSA was analyzed using UV, synchronous fluorescence and three-dimensional fluorescence under different pH conditions. These results showed that the binding of B12 to BSA causes apparent change in the secondary and tertiary structures of BSA.