刷状结构的阳离子性接枝微粒QPDMAEMA/SiO_2对牛血清白蛋白的吸附特性

以微米级硅胶微粒为基质,通过接枝聚合和大分子反应,制备了具有刷状结构的阳离子性接枝微粒,深入研究了其对牛血清白蛋白(BSA)的强吸附能力、吸附机理和吸附热力学.首先使含叔胺基团的单体甲基丙烯酸二甲基氨基乙酯(DMAEMA)在硅胶微粒表面发生接枝聚合,制得接枝微粒PDMAEMA/SiO2,然后以氯乙胺为试剂,使接枝大分子PDMAEMA链中的叔胺基团发生季铵化反应,获得了具有刷状结构的阳离子聚电解质的功能接枝微粒QPDMAEMA/SiO2.测定了微粒QPDMAEMA/SiO2的zeta电位,实施了对BSA的等温吸附实验,考察了介质pH值、离子强度及温度对吸附作用的影响,研究了吸附热力学.研究结果表明,功能接枝微粒QPDMAEMA/SiO2比接枝微粒PDMAEMA/SiO2具有更高的zeta电位,在静电相互作用驱动下,微粒QPDMAEMA/SiO2对BSA具有很强的吸附能力.吸附容量随介质pH值的增大呈现先增大后减小的变化趋势,当pH值等于BSA的等电点(pI=4.7)时,具有最高的吸附容量(高达112 mg?g-1).以等电点为界,离子强度对吸附容量会产生完全相反的影响作用:当介质pH值小于BSA的等电点时,电解质浓度增大,吸附容量增高;当介质pH值等于BSA的等电点时,吸附容量几乎不随电解质的浓度发生变化.吸附过程熵值减小而且放出热量,是一个焓驱动的吸附过程.     

功能接枝微粒PVI—SiO2的制备及其吸附特性初探

在偶联剂7-（甲基丙烯酰氧）丙基三甲氧基硅烷的媒介作用下,在溶液聚合体系中,采用“接出”法将功能单体1一乙烯基咪唑（VI）接枝聚合于微米级硅胶微粒表面,制得了功能接枝微粒PVI—SiO2。采用红外光谱（FT—IR）、扫描电镜（SEM）及热失重分析（TGA）等方法对PVI—SiO2进行了表征;测定了接枝微粒的Zeta电位;考察研究了主要因素对接枝聚合的影响;初步探索了其对铬酸根负离子及重金属离子的吸附特性。研究结果表明：本接枝聚合体系亦呈现在固体微粒表面接枝聚合的一般规律,即已接枝到硅胶微粒表面的聚合物层,会对后续的接枝聚合产生阻隔作用;温度及引发剂用量等因素显著影响接枝度,在适宜条件下每100gPVI—SiO2接枝PVI21．63g。在较大的pH范围内,接枝微粒的Zeta电位为较大的正值,在静电相互作用下,接枝微粒对铬酸根离子会产生很强的吸附作用,吸附量可高达120mg／g;凭借配位鳌合作用,接枝微粒对重金属离子具有强的吸附能力。     

刷状结构的阳离子性接枝微粒QPDMAEMA/SiO2对牛血清白蛋白的吸附特性

以微米级硅胶微粒为基质, 通过接枝聚合和大分子反应, 制备了具有刷状结构的阳离子性接枝微粒, 深入研究了其对牛血清白蛋白(BSA)的强吸附能力、吸附机理和吸附热力学. 首先使含叔胺基团的单体甲基丙烯酸二甲基氨基乙酯(DMAEMA)在硅胶微粒表面发生接枝聚合, 制得接枝微粒PDMAEMA/SiO₂, 然后以氯乙胺为试剂, 使接枝大分子PDMAEMA链中的叔胺基团发生季铵化反应, 获得了具有刷状结构的阳离子聚电解质的功能接枝微粒QPDMAEMA/SiO₂. 测定了微粒QPDMAEMA/SiO₂的zeta 电位, 实施了对BSA的等温吸附实验, 考察了介质pH值、离子强度及温度对吸附作用的影响, 研究了吸附热力学. 研究结果表明, 功能接枝微粒QPDMAEMA/SiO₂ 比接枝微粒PDMAEMA/SiO₂ 具有更高的zeta 电位, 在静电相互作用驱动下, 微粒QPDMAEMA/SiO₂对BSA具有很强的吸附能力. 吸附容量随介质pH值的增大呈现先增大后减小的变化趋势,当pH值等于BSA的等电点(pI=4.7)时, 具有最高的吸附容量(高达112 mg·g^-1). 以等电点为界, 离子强度对吸附容量会产生完全相反的影响作用: 当介质pH值小于BSA的等电点时, 电解质浓度增大, 吸附容量增高; 当介质pH值等于BSA的等电点时, 吸附容量几乎不随电解质的浓度发生变化. 吸附过程熵值减小而且放出热量,是一个焓驱动的吸附过程.     

接枝微球PMAA-HEMA/NVP对溶菌酶的吸附行为与吸附机理

采用反相悬浮聚合法制备了甲基丙烯酸羟乙酯(HEMA)与N-乙烯基吡咯烷酮(NVP)的交联共聚微球HEMA/NVP,然后采用"接出"法,实施了甲基丙烯酸(MAA)在交联微球表面的接枝聚合,制得了接枝微球PMAA-HEMA/NVP.以溶菌酶(LYZ)为模型碱性蛋白,深入研究了接枝微球PMAA-HEMA/NVP对碱性蛋白的吸附性能与吸附机理.测定了微球PMAA-HEMA/NVP的zeta电位,考察了PMAA接枝度、介质pH值及离子强度等因素对体系吸附性能的影响.结果表明,在较大的pH范围内,接枝微球PMAA-HEMA/NVP的zeta电位为绝对值较大的负值,即其表面携带有高密度的负电荷.在强静电相互作用的驱动下,接枝微球PMAA-HEMA/NVP对溶菌酶表现出很强的吸附能力.随介质pH值的增高,接枝微球对溶菌酶的吸附容量呈现先增大后减小的变化趋势,在与溶菌酶等电点接近的pH值处(pH=9),具有最大的吸附容量(90mg.g-1);离子强度对接枝微球的吸附能力也有较大的影响,当pH9时,溶菌酶吸附容量随NaCl浓度的增高而减小;当pH9时,吸附容量随NaCl浓度的增高而增大.     

功能接枝微粒PDMAEMA/SiO_2的制备及其吸附特性初探

凭借偶联剂γ-(甲基丙烯酰氧)丙基三甲氧基硅烷的媒介作用,在溶液聚合体系中,采用"接出"("graft from")法将单体甲基丙烯酸二甲氨基乙基酯(DMAEMA)接枝于硅胶微粒表面,制得了接枝微粒PDMAEMA/SiO2,重点考察了主要因素对接枝聚合的影响,并测定了接枝微粒的Zeta电位,初步考察了其吸附特性。研究结果表明,已接枝到硅胶表面的聚合物层,会对后续的接枝聚合产生阻隔作用;温度及引发剂用量等因素显著影响接枝度,在适宜条件下可制得接枝度为22g/100g的接枝微粒;在较大的pH范围内,接枝微粒的Zeta电位为较大的正值,在静电相互作用下,接枝微粒对铬酸根离子会产生强吸附作用.     

亚氨二乙酸型复合材料IDAA-PGMA/SiO2对重金属及稀土离子的吸附行为与吸附热力学

将甲基丙烯酸缩水甘油酯(GMA)接枝于硅胶微粒表面,制得了接枝微粒PGMA/SiO₂; 使亚氨二乙酸(IDAA)与接枝PGMA的环氧基团发生开环反应, 从而将亚氨二乙酸基团引入接枝微粒表面, 制得了复合螯合微粒材料IDAA-PGMA/SiO₂. 本文研究了IDAA-PGMA/SiO₂对重金属及稀土离子的螯合吸附行为, 深入地研究了吸附机理与吸附热力学. 研究结果表明: 凭借亚氨二乙酸基团与重金属离子之间的静电作用与配位螯合作用的协同, 复合微粒材料IDAA-PGMA/SiO₂对重金属离子可产生强的螯合吸附作用, 尤其对Pb²⁺离子表现出很强的螯合吸附能力, 常温下吸附容量可达0.235 g·g^-1; IDAA-PGMA/SiO₂对重金属离子的吸附过程为一放热过程, 且为焓驱动的过程, 升高温度, 吸附容量降低; 对稀土离子的吸附过程则为熵驱动的过程; 在可抑制金属离子水解的pH范围内, 介质的pH值越高, IDAA-PGMA/SiO₂的螯合吸附能力越强; IDAA-PGMA/SiO₂对重金属离子的吸附容量远高于对稀土离子的吸附容量.     

采用分子表面印迹技术构建手性空穴实现对天冬氨酸对映体的识别拆分

在溶液聚合体系中,采用"接出"法("graft from"method)将功能单体4-乙烯基吡啶(4VP)接枝聚合于微米级硅胶表面,制得了功能接枝微粒P4VP/SiO2,采用本课题组建立的新型分子表面印迹技术,以天冬氨酸(Asp)的一种对映体L-Asp为模板分子,二溴己烷为交联剂,对接枝在硅胶表面的大分子P4VP实施了分子印迹,制备了L-Asp分子表面印迹材料MIP-P4VP/SiO2.以天冬氨酸另一种对映体D-Asp为对比物,采用静态与动态两种方法深入研究了MIP-P4VP/SiO2对L-Asp分子的识别性能,重点探索了采用MIP-P4VP/SiO2对天冬氨酸两种对映体进行拆分的可行性.实验结果表明,印迹材料MIP-P4VP/SiO2对模板分子L-Asp具有良好的识别选择性与结合亲和性,相对于D-Asp,识别选择性系数为3.85,对天冬氨酸的外消旋体具有良好的拆分性能.印迹材料MIP-P4VP/SiO2也具有良好的解吸性能,以稀NaOH水溶液作为洗脱液,12个床体积内解吸率即可达到98.52%.     

螯合吸附材料PAO/SiO_2对重金属离子的螯合吸附行为

将丙烯腈接枝聚合在微米级硅胶微粒表面,经偕胺肟化转变,制得了接枝有聚偕胺肟(PAO)的复合型螯合吸附材料PAO/SiO2。本文重点考察了螯合吸附材料PAO/SiO2对几种重金属离子的螯合吸附行为,深入地研究了吸附机理。研究结果表明,偕胺肟基团与重金属离子之间的静电作用与配位螯合作用的协同,导致PAO/SiO2对重金属离子产生强的螯合吸附作用。在可抑制金属离子水解的pH范围内,介质的pH值越高,PAO/SiO2的螯合吸附能力越强;PAO/SiO2对性质不同的金属离子的吸附性能是有差别的,吸附容量的顺序为Cu2+Ni2+Pb2+Cd2+。     

接枝微粒PMAA/SiO2在水介质中对杀虫剂抗蚜威的吸附机理

以硅胶表面接枝聚甲基丙烯酸(PMAA)的复合型功能微粒PMAA/SiO2为固体吸附剂, 对水介质中的抗蚜威进行了静态吸附实验, 通过考察温度、pH值及盐度(NaCl浓度)对吸附容量的影响, 重点研究了PMAA/SiO2对抗蚜威的吸附机理. 为确认所提出的机理的正确性, 还采用紫外光谱吸收法, 研究了单体甲基丙烯酸与抗蚜威之间的相互作用, 也考察了在非水介质CCl4中PMAA/SiO2对抗蚜威的吸附作用. 研究结果表明, PMAA/SiO2对抗蚜威具有强的吸附作用, 吸附的驱动力是氢键、静电以及疏水相互作用三种作用的协同, 其中主驱动力是静电相互作用. 温度升高, 吸附容量减小; 盐度增大, 吸附容量降低; 当pH<8时, 吸附容量随pH升高而增大; 当pH>8时, 吸附容量随pH升高而减小; 当pH=8 时,吸附容量最大.     

接枝微粒PMAA/SiO2对胆红素吸附性能的研究

采用溶液聚合法将甲基丙烯酸(MAA)接枝于硅胶微粒表面,制得了接枝微粒PMAA/SiO2；并通过静态吸附实验研究了该功能微粒对胆红素的吸附性能,考察了介质pH值、离子强度及温度等因素对吸附性能的影响,研究了在牛血清白蛋白(BSA)存在下该微粒的吸附性能.静态吸附实验结果表明,接枝微粒PMAA/SiO2对胆红素具有较强吸...     

Shape control of anatase TiO2 nanoparticles by amino acids in a gel-sol system

Ellipsoidal anatase TiO2 nanoparticles of different aspect ratios were obtained by the gel-sol method in the presence of amino acids in which the resulting particles were basically single crystals, but highly rough surfaces or partly polycrystalline structures were observed with a high concentration of glutamic acid or aspartic acid.     

Thermoanalytical study of acid-treated clay containing amino acid immobilized on its surface

The aim of this study is to investigate the incorporation of amino acid molecules in an acid-activated montmorillonite by means of solid characterization after the incorporation of these biomolecules. The acid activation procedure was carried out for the purpose of increasing the acid sites in the clay as well as the impurity elimination in the mineral. Cysteine, aspartic, and glutamic acids were adsorbed on montmorillonite K10 which was previously treated with a hydrochloric acid solution. The clay was put in contact with amino acid solutions at two different concentrations. Each amino acid was adsorbed at identical conditions, with the pH fixed to ensure the charge of molecules and surface clay. The solid was characterized by means of X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption at 77 K. After the amino acid adsorption, the powders showed changes in their characteristics as well as in their thermal behavior, which depended on both the concentration and the nature of the adsorbed amino acid. The thermal decomposition and elimination of cysteine occurred at a higher temperature than the aspartic and glutamic acid; the complete removal of glutamic acid molecules was not observed at 850 °C. The differences observed in the solid characteristic after the adsorption of each amino acid were discussed. Both the thermoanalytical study and characterization of materials after the interaction with amino acid molecules can be useful to understand the adsorption mechanism of biomolecules on solid surfaces.     

Adsorption Behavior of Amino Acids on a Stainless Steel Surface

The adsorption behavior of various amino acids on a stainless steel surface was investigated at 30 degrees C and over a pH range of 3-10. Acidic and basic amino acids except histidine adsorbed remarkably at pH 3-4 and 7-10, respectively, and showed Langmuir-type adsorption isotherms. The effects of pH and ionic strength on the adsorption isotherms were investigated to analyze the interactions between amino acids and adsorption sites on the stainless steel. Hydrophobic amino acids and glycine showed only small adsorbed amounts at all pHs tested. For the acidic and basic amino acids, reversibility of the absorption and the influence of the ionic strength on the adsorption behavior were examined. The adsorption isotherms of the derivatives of aspartic acid were also measured in order to examine the contribution of the carboxylic groups of acidic amino acids to the adsorption. Furthermore, a Fourier-transform infrared spectroscopic analysis and semiempirical molecular orbital calculation were carried out to analyze the ionization states and the configuration of the amino acids adsorbed on a stainless steel surface. These investigations suggest that the acidic and basic amino acids adsorb through two electrostatic interactions of two ionized groups in the amino acid with a stainless steel surface. Copyright 2000 Academic Press.     

聚乙烯醇接枝微粒对黄酮类物质的吸附特性

以硅胶表面接枝有聚乙烯醇(PVA)的接枝微粒PVA/SiO₂为固体吸附剂, 对槲皮素和芦丁2种黄酮类化合物进行了吸附研究, 结果表明, 由于接枝微粒PVA/SiO₂表面含有高密度的羟基, 使得该接枝微粒与黄酮类化合物分子之间可形成多位点的常规氢键和π型氢键, 溶剂的竞争吸附对黄酮化合物的吸附容量产生很大的影响. 以弱极性的1,2-二氯乙烷(DCE)为溶剂时, 几乎不存在溶剂的竞争吸附, 槲皮素和芦丁具有最高的吸附容量, 分别为0.32 mmol/g(96 mg/g)和0.23 mmol/g(140 mg/g); 而在质子溶剂乙醇中, 强烈的溶剂竞争吸附使两者的吸附容量降至0.22 mmol/g(65 mg/g)和0.14 mmol/g(87 mg/g). 升高温度会减弱氢键作用, 甚至使氢键断裂, 导致吸附容量减小. 质子溶剂中电解质的存在, 对吸附作用产生负性影响. 功能微粒PVA/SiO₂对黄酮类化合物的吸附为放热过程, 且为焓驱动的吸附过程.     

Enhanced and selective adsorption of mercury ions on chitosan beads grafted with polyacrylamide via surface-initiated atom transfer radical polymerization

Enhanced and selective removal of mercury ions was achieved with chitosan beads grafted with polyacrylamide (chitosan-g-polyacrylamide) via surface-initiated atom transfer radical polymerization (ATRP). The chitosan-g-polyacrylamide beads were found to have significantly greater adsorption capacities and faster adsorption kinetics for mercury ions than the chitosan beads. At pH 4 and with initial mercury concentrations of 10-200 mg/L, the chitosan-g-polyacrylamide beads can achieve a maximum adsorption capacity of up to 322.6 mg/g (in comparison with 181.8 mg/g for the chitosan beads) and displayed a short adsorption equilibrium time of less than 60 min (compared to more than 15 h for the chitosan beads). Coadsorption experiments with both mercury and lead ions showed that the chitosan-g-polyacrylamide beads had excellent selectivity in the adsorption of mercury ions over lead ions at pH < 6, in contrast to the chitosan beads, which did not show clear selectivity for either of the two metal species. Mechanism study suggested that the enhanced mercury adsorption was due to the many amide groups grafted onto the surfaces of the beads, and the selectivity in mercury adsorption can be attributed to the ability of mercury ions to form covalent bonds with the amide. It was found that adsorbed mercury ions on the chitosan-g-polyacrylamide beads can be effectively desorbed in a perchloric acid solution, and the regenerated beads can be reused almost without any loss of adsorption capacity.     

Evaluation of the synergistic effect with amino acids for enantioseparation of basic drugs using capillary electrophoresis

The synergistic effect of two acidic amino acids, aspartic and glutamic acid, on the electrophoretic enantioseparation of four basic drugs was evaluated in the BGE containing a CD and at different pHs. Chlorpheniramine, hydroxyzine, propranolol and tramadol were used as the basic model drugs. However, no enantioseparations were achieved with a BGE containing sole amino acid, but the combined use of an acidic amino acid and a CD showed improved enantioseparations (synergistic effect) compared with the single CD system. The results demonstrated that at optimized pH, the electrostatic interactions of the anionic amino acids with the positively charged basic drugs could result in a decrease of the analyte migration velocity and it consequently improved the enantioseparation. The effective parameters such as the amino acid and chiral selector type and concentration, buffer pH, applied voltage, and capillary temperature were optimized. Favorable enantiomeric resolution and migration times of the model drugs were achieved with a 100 mM phosphate buffer solution (pH 3.0) containing 5.0 mM HP‐α‐CD/HP‐β‐CD and 20 mM aspartic acid with an 18 kV applied voltage at 25°C. ¹H NMR experiments were also carried out in a mixture of an analyte and CD in the absence and presence of aspartic acid. The NMR results were consistent with the results obtained by CE which showed the synergistic effect of amino acid.     

Adsorption kinetics and thermodynamics of acid dyes on a carboxymethylated chitosan-conjugated magnetic nano-adsorbent

The monodisperse chitosan-conjugated Fe(3)O(4) nanoparticles with a mean diameter of 13.5 nm were fabricated by the carboxymethylation of chitosan and its covalent binding onto Fe(3)O(4) nanoparticles via carbodiimide activation. The carboxymethylated chitosan (CMCH)-conjugated Fe(3)O(4) nanoparticles with about 4.92 wt.-% of CMCH had an isoelectric point of 5.95 and were shown to be quite efficient as anionic magnetic nano-adsorbent for the removal of acid dyes. Both the adsorption capacities of crocein orange G (AO12) and acid green 25 (AG25), as the model compounds, decreased with increasing pH, and the decreasing effect was more significant for AO12. On the contrary, the increase in the ionic strength decreased the adsorption capacity of AG25 but did not affect, obviously, the adsorption capacity of AO12. By the addition of NaCl and NaOH, both AO12 and AG25 could desorb and their different desorption behavior could be attributed to the combined effect of pH and ionic strength. From the adsorption kinetics and thermodynamics studies, it was found that both the adsorption processes of AO12 and AG25 obeyed the pseudo-second-order kinetic model, Langmuir isotherm, and might be surface reaction-controlled. Furthermore, the time required to reach the equilibrium for each one was significantly shorter than those using the micro-sized adsorbents due to the large available surface area. Also, based on the weight of chitosan, the maximum adsorption capacities were 1 883 and 1 471 mg x g(-1) for AO12 and AG25, respectively, much higher than the reported data. Thus, the anionic magnetic nano-adsorbent could not only be magnetically manipulated but also possessed the advantages of fast adsorption rate and high adsorption capacity. This could be useful in the fields of separation and magnetic carriers. [formula in text].