Adsorption and desorption of lysozyme on nano-sized magnetic particles and its conformational changes

Adsorption and desorption of lysozyme on nano-sized magnetic particles and its conformational change were studied in this work. Adsorption of lysozyme on nano-sized magnetic particles (Fe₃O₄) was carried out at different pH. Maximum adsorption of lysozyme (4.65 mg/m²) occurred at its isoelectric point (pI=11.1). Differential scanning calorimetry (DSC) results show that the lysozyme adsorbed on magnetic particles did not show any thermal transition over the range 20–100 °C. High desorption of lysozyme from magnetic particles was achieved using NaH₂PO₄ (pH 4.0) (90%) and NaSCN (pH 6.0) (97%) as desorbents. The conformational change of the lysozyme desorbed by NaH₂PO₄ was small, while the lysozyme desorbed by NaSCN underwent a significant conformational change as measured by the intrinsic fluorescence. Eighty-eight and 82% activity was retained in the desorbed enzyme for desorption by NaH₂PO₄ and NaSCN, respectively.     

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.     

Thermosensitive polymer (N-isopropylacrylamide) coated nanomagnetic particles: preparation and characterization

Thermosensitive polymer coated nanomagnetic adsorbents were synthesized by seed polymerization using surface modified nanomagnetic particles as the seeds. The Fe3O4 nanomagnetic particles were prepared by chemical precipitation of Fe2+ and Fe3+ salts in the ratio of 1:2 under alkaline and inert condition. The surface of these particles was modified by surfactants to achieve stability against agglomeration. These stable particles were then polymerized using N-isopropylacrylamide (NIPAM) as the main monomer, methylene-bis-acrylamide as the crosslinker and potassium per sulfate as the initiator. The thermosensitive adsorbents were characterized by using transmission electron micrography (TEM) and vibrating sample magnetometer (VSM). TEM showed that the particle remained discrete with a mean diameter of 12 nm. Magnetic measurements revealed that the particles are superparamagnetic only with a decrease of magnetism after binding with the polymer due to the increase in surface spin disorientation. Pure Fe3O4 spinel structure of these nanoparticles was indicated by the X-ray diffraction (XRD) patterns. The polymerization of NIPAM with the surface modified nanomagnetic particles was confirmed by Fourier transform spectroscopy (FTIR), Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). In addition, the adsorption/desorption of BSA molecule on these thermosensitive nanoparticles was investigated as a function of temperature. More than 60% desorption efficiency was achieved under appropriate condition.     

Interfacial properties of amiodarone: the stabilizing effect of phosphate anions

Amiodarone, a drug used in heart therapy, is poorly soluble in water at room temperature, but forms transparent phases much more concentrated than the critical micellar concentration (CMC), when crystals are heated (above 60 degrees C) in presence of water and cooled down to room temperature. These pseudosolutions were supposed to be made of a complex system of micelles. In order to better understand the effects of pH and ion species on the supramolecular organization of amiodarone, interfacial pressure measurements were performed at the air/water interface on a Langmuir trough. Monolayers spread from chloroformic solutions over non bufferered subphases were insoluble at basic pH (NaOH, pH 10) but soluble at acidic pH (HCl, pH 4). However, a higher ionic strength obtained by adding NaCl (0.15 N) or NaH(2)PO(4) (0.15 N) to the subphase stopped the amiodarone solubilization. On an acidic phosphate subphase (NaH(2)PO(4), pH 4.4, 0.15 N), abnormally high surface pressures (>1 mN/m) were measured for high molecular areas (80-200 ?(2)/molecule) suggesting a supramolecular organization of the surface film. Insoluble monolayers were also obtained when the amiodarone supramolecular pseudosolution was spread on neutral (NaH(2)PO(4), pH 6.25, 0.15 N) or acidic (NaH(2)PO(4), pH 4.4, 0.15 N) subphases. However, a great instability on basic subphase (phosphate buffer pH 8.8) indicated the breakage of the supramolecular structure during spreading. These results are discussed taking into account the amiodarone state of ionization and the electrostatic interactions with counterions. Combining the use of phosphate counterions and that of acidic pH opens new perspectives in the optimization of amiodarone intravenous formulations.     

Preparation of Polymer Particles Coated with Hydroxyapatite

Polymer particles coated with hydroxyapatite were prepared by treating Pd0 immobilized polystyrene-co-acrylic acid particles in aqueous CaCl2 and NaH2PO2 solutions. Hydroxyapatite coating took place at neutral to alkaline pH conditions, and the homogeneous growth of the hydroxyapatite layer on the surface of polymer particles was observed at relatively low temperature (30-50 degrees C). The thickness of the hydroxyapatite layer increased with reaction time. Copyright 1999 Academic Press.     

Conformational change of adsorbed and desorbed bovine serum albumin on nano-sized magnetic particles

Adsorptions of bovine serum albumin (BSA) on nano-sized magnetic particles with and without the presence of carbodiimide were studied. Desorption of BSA from magnetic particles were carried out in either NaOH or Na₂HPO₄ solutions. The structures of native BSA, adsorbed BSA on magnetic particles, and desorbed BSA were studied by several methods, circular dichroism (CD), fluorescence spectroscopy and differential scanning calorimetry (DSC). The magnitude of conformational changes of protein was determined by calculating the α-helix content from the circular dichroism (CD) spectra and by evaluating fluorescence spectrum and DSC thermograms. Adsorbed BSA on magnetic particles shows no thermal transition with respect to the native BSA. The structural change of BSA when desorbed by Na₂HPO₄ solution is much smaller in comparison to that when desorbed by NaOH solution. Hence, this indicates that BSA could be desorbed from nano-sized magnetic particles using Na₂HPO₄ without much conformational change.     

Comparison of adsorption performances of metal–chelated polyamide hollow fibre membranes in lysozyme separation

Commercially available microporous polyamide hollow fibres are modified by acid hydrolysis to activate the reactive groups and subsequently binding of the ligand, i.e. Cibacron Blue F3GA. Then the Cibacron Blue F3GA-derived hollow fibres were loaded with different metal ions (i.e. Zn(II), Cu(II), Ni(II)) to form the metal chelate. The internal polymer matrix was characterised by scanning electron microscopy. The effects of pH, initial concentration of lysozyme, metal type and temperature on the adsorption of lysozyme to the metal–chelated hollow fibres were examined in a batch reactor. The non-specific adsorption of lysozyme onto the polyamide hollow fibres was 1.8 mg/g. Cibacron Blue F3GA immobilisation increased the lysozyme adsorption up to 62.3 mg/g. Metal–chelated hollow fibres showed a significant increase of the adsorption efficiency. Lysozyme adsorption capacities of Zn(II), Cu(II) and Ni(II)-chelated hollow fibres were different. The maximum capacities of Zn(II), Cu(II) or Ni(II)-chelated hollow fibres were 144.2, 75.2 and 68.6 mg/g, respectively. Significant amount of the adsorbed lysozyme (up to 97%) was eluted in 1 h in the elution medium containing 1.0 M NaSCN at pH 8.0 and 25 mM EDTA at pH 4.9. Repeated adsorption–desorption process showed that this novel metal–chelated polyamide hollow fibres are suitable for lysozyme adsorption.     

酸性化学镀镍中次亚磷酸钠阳极氧化行为的研究

采用线性电位扫描和交流阻抗法研究了酸性化学镀镍过程中还原剂次亚磷酸钠的阳极氧化行为。结果表明,次亚磷酸钠的氧化是一个复杂的电化学过程,其阳极氧化行为受本身浓度、溶液温度、阳极扫描速度以及Ｎｉ＾２＋的影响,在其氧化反应之前可能存在异相界面转化步骤,该步骤成为整个氧化过程的控制步骤。     

Analysis and confirmation of synthetic anorexics in adulterated traditional Chinese medicines by high-performance capillary electrophoresis.

Six synthetic anorexics, clobenzorex, diethylpropion, fenfluramine, methamphetamine, phenylpropanolamine and phentermine, which can be found as adulterants in traditional Chinese medicines were assayed simultaneously by high-performance capillary electrophoresis. The electrolyte was a buffer solution containing 120 mM phosphate buffer (NaH2PO4/H3PO4, pH 2.0) and 15% acetonitrile. Applied voltage was 16 kV and temperature was 30 degrees C. Fluoren-2,7-diammonium chloride was used as an internal standard and detector set at 200 nm. The recoveries of the synthetic anorexic adulterants in traditional Chinese medicinal formula using C8-SCX mixed solid-phase extraction were studied. Several traditional Chinese medicinal powders obtained from clinics were also studied by the above HPCE method and confirmed by GC-MS. Clobenzorex, diethylpropion and fenfluramine were found and determine in these samples.     

芦丁在离子液体双水相中分配性能

建立了室温离子液体四氟硼酸1-丁基-3-甲基咪唑([Bmim]BF4)和NaH2PO4组成的双水相萃取体系并用于对芦丁的萃取分离研究。考察了离子液体用量、芦丁的浓度、盐的加入量、溶液酸度和加入其它物质对芦丁在两相中分配的影响。结果表明,离子液在1.0~2.5 mL,磷酸二氢钠加入量在1.0~2.0 g,加入卢丁溶液0.5~2.5 mL,酸度在pH值为2~7范围,卢丁在离子液体双水相体系中有较高的萃取率(E%>90)。除阳离子表面活性剂外,其余大部分物质不影响相比和卢丁的测定。离子液相中卢丁的最大吸收波长为358 nm,与乙醇水溶液中比较,最大吸收波长发生紫移,表明离子液与卢丁发生了作用。利用离子液体双水相体系,测定了银杏叶中卢丁的含量。     

纳米金标记-膜过滤分光光度法检测免疫球蛋白G

采用10 nm的纳米金标记羊抗人免疫球蛋白G获得免疫球蛋白G(IgG)的探针(AuIgG)。在pH 6.8的NaH2PO4-Na2HPO4磷酸盐缓冲溶液及聚乙二醇6000、KCl溶液存在下,IgG与AuIgG探针发生免疫反应,用0.15μm滤膜过滤反应生成的免疫复合物溶液,滤液在524 nm处有一最大吸收峰。其降低值ΔA524 nm随着IgG浓度的增加线性增加,据此建立了一种测定IgG的分光光度法。在最佳实验条件下,免疫球蛋白G浓度在0.025~0.375μg/mL范围内与ΔA呈良好的线性关系,其线性回归方程为ΔA=0.783ρ+0.0232,相关系数为0.9927,检出限(3σ)为0.0082μg/mL。该法用于分析人血清中免疫球蛋白G,结果与免疫透射比浊法结果一致,相对标准偏差在2.0%~5.6%之间。     

十二烷基苯磺酸钠与苯酚的导数同步荧光法同时测定

研究了十二烷基苯磺酸钠和苯酚及其混合物在pH 6.0的磷酸二氢钠-磷酸氢二钠缓冲液中的一阶导数同步荧光光谱,确定了最佳实验条件:波长差Δλ=60 nm,十二烷基苯磺酸钠的测定波长为224 nm,苯酚的测定波长为258 nm,建立了一阶导数同步荧光法同时测定混合物中十二烷基苯磺酸钠和苯酚的新方法。十二烷基苯磺酸钠和苯酚的线性范围分别为0.05~8.00 mg/L和0.10~5.50 mg/L;线性相关系数分别为0.995 5和0.999 7;检出限分别为8.4μg/L和5.3μg/L;回收率分别为95%~100%和98%~102%;相对标准偏差分别为3.8%和1.9%。该方法可用于水中十二烷基苯磺酸钠和苯酚的同时检测,结果满意。     

超细非晶镍合金的化学制备及类金属元素对性质的影响

常温下分别使用KBH4和NaH2PO2在水溶液中还原Ni^2^+制得了Ni65B35和Ni89P11超细非晶合金(UFAAP), 同时使用KBH4和NaH2PO2还原Ni^2^+制得了Ni73P13B14UFAAP. Ni-P的粒径较大, 约为110nm, Ni-B的粒径较小, 约为20nm,Ni-P-B的粒径居其之间, 约为40nm。XPS表明, Ni-P间的相互作用强于Ni-B间的相互作用, Ni-P-B中P的电子状态与Ni-P中的相似。Ni-P-B比Ni-P的比表面积高得多,Ni-P-B比Ni-B和Ni-P具有更好的非晶态稳定性, 在573K热处理, 它的非晶态保持完好。晶化结果也表明Ni-P-B中Ni-P间的相互作用比Ni-B间的强。     

相转化对均匀胶粒的形貌及团聚度的影响

金属盐溶液高温强迫水解是制备均分散胶体粒子的重要手段K’1．多年来人们致力于制备方法的研究，并对形成机理也有较系统的讨论．就。－FeZ（此胶粉的形成而言；张玉亭门和Moral，s山先后研究了0．02mol·L－’的F，CI。－HCI及FeCI。－NaH。PO。体系经100t陈化制备均匀球形和     

掺杂ZrO＿2的Pt／Al＿2O＿3表面氧性质及一氧化碳氧化性能研究

用ＴＰＤ－ＭＳ、ＴＰＳＲ－ＭＳ及ＣＯ氧化活性测定等方法研究了Ｐｔ／Ａｌ２Ｏ３和掺杂超细ＺｒＯ２的样品的表面氧脱出－恢复性能、ＣＯ表面氧化性能及催化氧化性能．结果表明，在Ｐｔ／Ａｌ２Ｏ３中掺杂ＺｒＯ２后，样品表面上的氧物种脱出和氧化恢复性能明显提高，脱氧量也明显增大；并发现在ＣＯ－ＴＰＳＲ过程中程脱物ＣＯ２的脱附量大小及峰顶温度次序与对ＣＯ的催化氧化活性也有一致的关系     

化学镀镍过程中丙酸作用的机理研究

利用循环伏安法和红外漫反射光谱法研究化学镀镍过程中丙酸的作用机理. 不同丙酸浓度下的循环伏安曲线表明,丙酸能同时促进Ni^2＋的还原和H₂PO^-₂的氧化.根据丙酸分别与NaH₂PO₂和NiSO₄共存时镍基体上吸附物的红外漫反射光谱变化,推断丙酸是通过与NaH₂PO₂和Ni^2＋形成表面络合物来促进化学沉积的. 丙酸能与NaH₂PO₂形成分子间氢键,促使P-H键断裂并生成·PHO^-₂中间物,从而提高H₂PO^-₂的氧化速度; 同时,丙酸以其-OCO-官能团与Ni^2＋生成桥式配合物,有利于加速Ni^2＋的沉积. H₂PO^-₂氧化速度的提高有助于磷的沉积,从而增大了化学镀层中的磷含量.     

Electrospray ionization tandem mass spectrometric study of salt cluster ions: part 2--salts of polyatomic acid groups and of multivalent metals

Salt cluster ions formed from 0.05 M solutions of CaCl(2), CuCl(2) and Na(A)B (where A = 1 or 2 and B = CO(3)(2-), HCO(3)(-), H(2)PO(4)(-) and HPO(4)(2-)) were studied by electrospray ionization tandem mass spectrometry. The effects on salt cluster ions of droplet pH and of redox reactions induced by electrospray provide information on the electrospray process. CaCl(2) solution yielded salt cluster ions of the form (CaCl(2))(n)(CaCl)(x)(x+) and (CaCl(2))(n)(Cl)(y)(y-), where x, y = 1-3, in positive- and negative-ion modes, respectively. Upon collision induced dissociation (CID), singly charged CaCl(2) cluster ions fragmented, doubly charged cluster ions generated either singly or both singly and doubly charged fragment ions, depending on the cluster mass, and triply charged clusters fragmented predominantly by the loss of charged species. CuCl(2) solution yielded nine series of cluster ions of the form (CuCl(2))(n)(CuCl)(m) plus Cu(+), CuCl(+), or Cl(-). CuCl, the reductive product of CuCl(2), was observed as a neutral component of positively and negatively charged cluster ions. Free electrons were formed in a visible discharge that bridged the gap between the electrospray capillary and the sampling cone brought about the reduction of Cu(2+) to Cu(+). Upon CID, these cluster ions fragmented to lose CuCl(2), CuCl, Cl, and Cl(2). Na(2)CO(3) and NaHCO(3) solutions yielded cluster ions of the form (Na(2)CO(3))(n) plus Na(+) or NaCO(3)(-). Small numbers of NaHCO(3) molecules were found in some cluster ions obtained with the NaHCO(3) solution. For both Na(2)HPO(4) and NaH(2)PO(4) solutions, ions of the form (Na(2)HPO(4))(h), (NaH(2)PO(4))(i), (Na(3)PO(4))(j), (NaPO(3))(k) plus Na(+), PO(3)(-) or H(2)PO(4)(-) were observed. In addition, ions having one or two phosphoric acid (H(3)PO(4)) molecules were observed from the NaH(2)PO(4) solution while ions containing one sodium hydroxide (NaOH) molecule were observed from the Na(2)HPO(4) solution. The cluster ions observed from these four salts of polyatomic acid groups indicate that changes in pH occur in both directions during the electrospray process principally by solvent evaporation; the pH value of the acidic solution became lower and that of the basic solution higher.     

Selective adsorption of phosphate from seawater and wastewater by amorphous zirconium hydroxide

Phosphate adsorption from single electrolyte (NaH2PO4), phosphate-enriched seawater, and model wastewater was studied using amorphous zirconium hydroxide, ZrO(OH)2(Na2O)0.05 1.5H2O, as an adsorbent. Batch experiments were carried out to investigate the adsorption of phosphate. The effect of pH on phosphate adsorption from seawater showed that the uptake of phosphate increased with an increase in pH up to 6, and then decreased sharply with a further increase in pH of the solution. The equilibrium data of phosphate adsorption were followed with a Freundlich isotherm. The uptake of phosphate at the adsorbent/solution ratio 0.05 g/2 L was 10 and 17 mg-P/g for the phosphate-enriched seawater and the model wastewater, respectively. A much higher adsorptivity toward phosphate ions in seawater was observed on ZrO(OH)2(Na2O)0.05 1.5H(2)O than on other representative adsorbents based on layered double hydroxides of Mg(II)-Al(III), Mg(II)-Fe(III), and Ni(II)-Fe(III). The effective desorption of phosphate ions on ZrO(OH)2(Na2O)0.05 1.5H2O could be achieved using a 0.1 M NaOH solution. The usefulness of experimental data for practical applications in removing phosphate in seawater and wastewater is discussed.     

ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE

The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4^- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0,respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus,the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm^-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here.     

高效液相色谱法分离和测定酒石酸和马来酸

１引言 酒石酸（２,３一二羟基丁二酸）和马来酸（顺丁烯二酸）都是重要的有机化工原料,它们被广泛地应用于有机合成和其它化工生产领域［１］． 酒石酸的制备常用钨酸作为催化剂,由马来酸识水溶液与过氧化氢进行环氧化反应再经水解精制而成,其中常含有微量的没有反应的马来酸,因此,建立有效的分离和测定酒石酸和马来酸的方法,对于酒石酸生产条件的选择与控制,以及产品的质量检测等都有十分重要的意义． 目前尚未发现有关同时分离和测定酒石酸和马来酸的文献报道．我们首次采用反相高效液相色谱法,跟踪监测了酒石酸生产过程中的物…