氨基酸在固体表面的吸附*

介绍了氨基酸在固体表面吸附的常见吸附模式和吸附等温线类型。在常见的等温式中Sips等温式能处理液相中吸附质浓度从低到高、吸附剂表面从均匀到不均匀等各种情形下的固/液吸附体系,得到的等温线一般归属4类：S型、L型、H型和C型;总结和讨论了各吸附参数对氨基酸吸附的影响,具体考察了氨基酸种类、固体表面的性质、溶剂种类、介质的pH、介质离子强度和温度等因素对氨基酸吸附的影响,指出通过优化各吸附参数,可以调整氨基酸和固体吸附剂之间的静电吸引力或疏水作用,达到最好的吸附效果;对氨基酸的固体吸附剂进行了分类阐述。     

接枝微粒材料P4VP-SiO_2对酸性氨基酸的吸附性能与吸附机理

将4-乙烯基吡啶(4VP)接枝聚合于微米级硅胶表面,制得了接枝有聚4-乙烯基吡啶(P4VP)的接枝微粒P4VP-SiO_2,测定了P4VP-SiO_2的红外光谱,袁征了其化学结构,并测定了该复合型功能微粒材料的Zeta电位.采用静态法研究了P4VP-SiO_2对酸性氨基酸天冬氨酸与谷氨酸的吸附性能,考察了介质pH、离子强度及温度对其吸附性能的影响,探索了吸附机理.研究结果表明:在较大的pH范围内,P4VP-SiO_2的Zeta电位为较高的正值,即微粒表面携带有高密度的正电荷;酸性氨基酸天冬氨酸与谷氨酸等电点都较低,所以在一般的介质pH范围内,它们的分子带有负电荷;凭借静电相互作用,P4VP-SiO_2对酸性氨基酸天冬氨酸与谷氨酸均表现出很强的吸附能力,而对中性与碱性氨基酸(在一般的介质pH范围内分子带有正电荷)的吸附能力则很弱;随介质pH的增大,P4VP-SiO_2对天冬氨酸与谷氨酸的吸附能力呈现先增强后减弱的规律,在pH＝4处,吸附容量具有最大值,分别为280 mg/g与230 mg/g;温度升高,吸附容量减小;盐度增大,吸附容量降低.     

Adsorption of Amino Acids on Cellulose Diacetate Membranes

Adsorption of a series of amino acids on cellulose diacetate membranes was studied. Adsorption isotherms were constructed and thermodynamic characteristics of adsorption (chemical potential of the adsorbent and Gibbs energy) were determined.     

Adsorption of Some Essential Amino Acids on Hydroxyapatite

Samples of synthetic hydroxyapatite, Ca(10)(PO(4))(6)(OH)(2), obtained by wet method and calcined at 1173 K in air were used in an adsorption study of some essential amino acids, mainly histidine, methionine, and tryptophan. Adsorption isotherms were obtained using aqueous solutions of concentration range 2.7x10(-2)-1.3x10(-3) M at 303, 318, and 343 K, under near neutral conditions. The mode of adsorption was studied using IR spectroscopy. The results are discussed in terms of the dependence of the adsorption process both on the functional groups on the hydroxyapatite and on the solution chemistry of the aqueous amino acids solutions. Copyright 2001 Academic Press.     

表面改性SUS316L不锈钢的电化学行为研究

分别以表面镀Rh,表面离子束增强沉积Ta2O5膜及溶胶凝胶法沉积TiO2膜对冠状动脉支架用材料SUS316L不锈钢进行表面改性.采用电化学方法研究了该表面改性试样在Tyrode's模拟人工体液中的电化学行为.结果表明,上述3种表面改性方法均可提高SUS316L不锈钢在模拟人工体液中的阳极极化性能.其中对于采用离子束增强法沉积的Ta2O5膜和溶胶凝胶法沉积的TiO2膜,因Ta和Ti上的d轨道空位已被氧的电子占据,不利于氢吸附,从而抑制了阴极的析氢过程.X射线衍射分析发现,3种改性方法在SUS316L不锈钢表面依次形成均匀而致密的Rh金属层,Ta2O5的无序膜层和TiO2晶态膜层,阻止了合金元素的溶解,改善不锈钢的电化学性能.     

微纳米多孔不锈钢表面高效吸附活性生物大分子

不锈钢(AISI 316L)是目前在医药器械中应用最为广泛的商业化材料. 下一代的不锈钢智能材料将特殊功能的生物活性分子(或纳米粒子)修饰在金属表面以模拟组织功能、提高生物/细胞相容性, 这是目前材料科学研究的热点领域之一. 本文研究了具有微纳米多孔表面结构的316L 不锈钢对抗体和生物酶分子的吸附作用,并与这些生物分子在光滑表面以及镀金表面的吸附进行了比较. 研究发现不锈钢可通过简单的电化学腐蚀方法在表面产生微纳米多孔结构. 微纳米孔不锈钢表面可稳定地吸附抗体或辣根过氧化物酶分子, 其吸附量与喷镀金表面相当或更好. 用表面活性剂(10%牛血清白蛋白(BSA)或0.2% Tween-20)洗涤不能除去吸附的蛋白.用5% Tween-20 预处理金属表面, 则可减少一半的抗体吸附量; 但表面活性剂预处理对辣根过氧化物酶的吸附没有影响. 吸附蛋白质后的金属表面湿润度大大增加; 蛋白质修饰的微纳米孔不锈钢表面表现出了很好的亲水性(水接触角小于50°), 指示了很好的生物相容性. 而金属表面的湿润度则主要取决于蛋白质物种, 并与蛋白质的吸附量正相关. 吸附于不锈钢微纳米孔表面的抗体仍保持了良好的生物活性; 用此种方式制备的抗CD34抗体修饰的不锈钢血管支架可以高密度并高选择性地吸附其目标细胞(如KG-1细胞). 本文工作为未来制备新型的无高聚物涂层的不锈钢智能医学生物材料提供了基础.     

Interfacial Behavior of beta-Lactoglobulin at a Stainless Steel Surface: An Electrochemical Impedance Spectroscopy Study

The electrochemical impedance spectroscopy technique was used to investigate the interfacial behavior of beta-lactoglobulin at an austenitic stainless steel surface over the temperature range 299 to 343 K at an open circuit potential. The electrode/electrolyte interface and corresponding surface processes were successfully modeled by applying an equivalent-electrical-circuit approach. A charge-transfer resistance value was found to be very sensitive to the amount of adsorbed protein (surface concentration), thus indicating that the adsorption of the protein (i) was accompanied by the transfer of the charge, via chemisorption, and (ii) influenced the mechanism and kinetics of the corrosion reaction. This was also apparent from the large decrease in the corrosion activation energy (16 kJ mol(-1)) caused by the adsorption of the protein. Adsorption of beta-lactoglobulin onto the stainless steel surface at an open circuit potential resulted in a unimodal isotherm at all the temperatures studied and the adsorption process was described with a Langmuir adsorption isotherm. From the calculated Gibbs free energies of adsorption it was confirmed that beta-lactoglobulin molecules adsorb strongly onto the stainless steel surface. The enthalpy and entropy values indicated that the molecule partially unfolds at the surface upon adsorption. The adsorption process was found to be entirely governed by the change in entropy. Copyright 2000 Academic Press.     

The Conformations of Amino Acids on a Gold(111) Surface

The interactions of amino acids with inorganic surfaces are of interest for biologists and biotechnologists alike. However, the structural determinants of peptide–surface interactions have remained elusive, but are important for a structural understanding of the interactions of biomolecules with gold surfaces. Molecular dynamics simulations are a tool to analyze structures of amino acids on surfaces. However, such an approach is challenging due to lacking parameterization for many surfaces and the polarizability of metal surfaces. Herein, we report DFT calculations of amino acid fragments in vacuo and molecular dynamics simulations of the interaction of all amino acids with a gold(111) surface in explicit solvent, using the recently introduced polarizable gold force field GolP. We describe preferred orientations of the amino acids on the metal surface. We find that all amino acids preferably interact with the gold surface at least partially with their backbone, underlining an unfolding propensity of gold surfaces.     

Calcium-Mediated Adsorption of Neutral Amino Acids to Carboxymethylated Chitin

Among various divalent metal ions, calcium has been found to be adsorbed tightly onto carboxymethylated chitin. The adsorption was completed not only by induced carboxyl groups but also by the support of acetamide, as well as primary and secondary hydroxyl groups. Although the adsorption capacity for transition metal ions was enhanced appreciably by regeneration into fibrous form, only that of calcium ion, among alkali-earth metals, was at the same level as that of transition metals. Since little effect was shown on the adsorption of phenylalanine by the blocking of α-amino and α-carboxyl groups of L-Phe, and since D-Phe was so a little adsorbed, the chiral specific adsorption of phenylalanine might be supported by mediation of calcium ion and by the contribution of hydrophobicity of the β-phenyl group.     

Effect of Structure on the Adsorption of Amino Acids on Copper Electrodes

The adsorption of amino acids on copper electrodes was studied at negative potentials. The effect of the amino acid structure on the mechanism and extent of adsorption was elucidated. Glycine, alanine, and asparagine molecules were found to reorient upon adsorption. An adsorption mechanism involving either neutral molecules or anions was proposed.     

交联壳聚糖对氨基酸的吸附性能

本文研究了交联壳聚糖对甘氨酸、谷氨酸和赖氨酸的吸附性能，吸附率依次为甘氨酸＞赖氨酸＞谷氨酸，并决定于上柱液的ＰＨ值及其浓度。用０．０５和０．１ｍｏｌ／ｌＮＨ４ＯＨ可以解吸。     

N2在Pd金属表面的吸附行为

对Pd原子采用相对论有效原子实势(RECP/SDD), N原子采用AUG-cc-pVTZ基函数, 利用B3LYP方法计算了PdN和PdN2分子的微观结构以及不同温度下的热力学函数. 以气态分子总能量中的振动能EV代替该分子处于固态时的振动能量, 以电子运动和振动运动熵SEV代替分子处于固态的熵的近似方法, 计算了不同温度下金属Pd与N2反应的ΔHӨ、ΔSӨ、ΔGӨ及氮化反应平衡压力, 导出了氮化反应平衡压力与温度的关系. 由此可看出, 在常压及298.15～998.15 K温度条件下, N2在金属Pd表面的吸附过程以Pd(s) + N2 = PdN2(s)反应进行. 计算得出在标准条件下, PdN(s)的生成焓为254.37 kJ·mol-1, PdN2(s)的生成焓为－80.59 kJ·mol-1. 并与Pd氢化反应平衡压力比较, 得到平衡常数Kp(N2)比Kp(H2)约小两个数量级, 说明N2较难被金属Pd表面吸附, 在热力学上有利于氢置换氮.     

芳香氨基酸在吸附树脂上的传质速度的研究

本文建立了测量芳香氨基酸在吸附树脂上传质速度的方法。引用Boyd方程模型测定了苯丙氨酸和酪氨酸的有效内扩散系数;研究了树脂结构与芳香氨基酸扩散速度之间的关系;同时考察了温度、pH值诸因素对扩散速度的影响。     

奥氏体不锈钢中氮的溶解行为

本文测定不同温度、氮分压和化学组成时奥氏体不锈钢中氮的溶解行为,为含氮奥氏体不锈钢生产过程中的氮含量控制提供了理论依据.     

疏水蛋白在云母表面的吸附

采用分子动力学模拟方法研究了疏水蛋白(HFBI)在亲水云母表面的吸附过程.通过6组平行的分子动力学模拟得到了2种不同的稳定吸附结构,即通过N端和通过亲水的α螺旋与表面吸附,得到了5种吸附残基.进一步用自适应偏置力方法计算了所有吸附残基与表面的结合自由能.结果表明,残基Lys是吸附过程的关键残基,即当HFBI通过含有Lys残基的α螺旋与云母表面作用时,其吸附构象最稳定.静电作用是吸附过程的主要驱动力.在该吸附结构中,HFBI的疏水面暴露在溶液中,有效降低了云母表面的润湿性.     

缓蚀剂在N80钢上吸附行为研究

应用极化曲线和交流阻抗技术研究了 4种缓蚀剂在N80钢基体和碳酸亚铁膜上的吸脱附行为 .实验表明 ,对同一种缓蚀剂 ,其在N80钢光洁表面和在腐蚀产物膜上的吸附力强度不同 ,而酸性缓蚀剂和小分子缓蚀剂在N80钢光洁金属表面和碳酸亚铁膜上各表现出不同的缓蚀行为     

Thermodynamic Behavior of Systems Containing Amino Acids in Aqueous-Lactose Solutions

The hydration of proteins plays a vital role in biological systems, which inspires us to study the molecular interactions in solutions containing amino acids + water + lactose at different temperatures. Therefore, in view of the biological implications of the hydration behavior of amino acids, in the present document we report the key thermodynamic properties: standard molar volumes, $$V_{2,phi }^{0}$$, and standard molar compressions, $$kappa_{S,2,phi }^{0}$$ of glycine, l-serine, l-proline, l-arginine and l-asparagine in 0.10, 0.30 and 0.50 mol·kg−1 aqueous solutions of lactose from density and ultrasonic velocity data at different temperatures, which helps us to understand the effect of lactose on the hydration of the amino acids. We have also reported refractive indices and molar refractions of the studied systems. The results reveal that lactose has a significant effect on the hydration and electrostriction behavior of the amino acids in general and has a dehydration effect in particular on the amino acids. The results have implications in the role of proteins in biological systems.     

氨基酸缓蚀剂在盐酸溶液中对钢的缓蚀作用

应用极化曲线、电化学阻抗谱等测试技术,研究了以谷氨酸作缓蚀剂在10%盐酸介质中对X65钢的缓蚀作用,测试腐蚀参数包括腐蚀电位(Ecorr)、极化电阻(Rp)、缓蚀效率(η)等.研究表明:该缓蚀剂是一种抑制阴极为主的混合型缓蚀剂,在较低的浓度具有良好缓蚀效果;缓蚀效率随着浓度的增加而提高,并在0.3g.L-1时达到最大值(90%以上).     

Electrochemical Behavior and Nonlinear Mott-Schottky Characterization of a Stainless Steel Passive Film

The electrochemical behavior of 304-stainless steel in solutions with different pH values and chloride concentrations was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and a nonlinear Mott-Schottky analysis method. The results showed that the corrosion behavior of 304-stainless steel was affected by various factors, such as pH, chloride ion concentration, and dissolved oxygen. The pit initiation and propagation stage were observed in EIS plots through the addition of sodium chloride. In addition, the effect of pH on the passive film dominated one of the film growth kinetic reactions. The effect of chloride ion concentration was caused by the generation of more cation vacancies, leading the passive film more susceptible to pitting, which was also demonstrated by X-ray Photoelectron Spectroscopy. The results are consistent with the point defect model.