反离子对牛血清白蛋白在荷电葡聚糖接枝介质中色谱行为的影响

从前期开发的具有极高的吸附容量及传质速率的二乙氨乙基葡聚糖接枝离子交换介质中选取FF-D50-DexD100和FF-DexD100为典型代表,利用Cl^-、SCN^-、SO₄^2-、HPO₄^2-为模型反离子,以牛血清白蛋白（BSA）为模型蛋白,以商品化介质（Q Sepharose FF、Q Sepharose XL、DEAE Sepharose FF）为对照,在离子强度为0.06mol/L下,系统研究反离子对二乙氨乙基葡聚糖接枝介质的蛋白质吸附与洗脱行为的影响。结果表明,二乙氨乙基葡聚糖接枝介质对不同反离子的偏好性存在差异,且该偏好性差异与基团所处位置（接枝链配基或表面配基）无关。同时,介质偏好性弱的反离子会通过促进二乙氨乙基葡聚糖接枝介质的“链传递”效应加快蛋白质的传质速率,从而提高动态吸附容量。因此,在使用二乙氨乙基葡聚糖接枝介质进行蛋白质色谱柱分离过程中,可在吸附操作中使用HPO₄^2-,在洗脱操作中使用SCN^-来优化分离效果。     

反离子对部分电荷中和的聚乙烯亚胺接枝介质的蛋白质色谱行为的影响

前期研究表明部分电荷中和的聚乙烯亚胺接枝琼脂糖介质FF-PEI-R440具有较高静态吸附容量和快速传质速率。本文选取硫氰酸根离子、氯离子、磷酸氢根离子以及硫酸根离子这4种反离子,在离子强度为0.03、0.06mol·L~(-1)下,研究其对FF-PEI-R440吸附与洗脱行为的影响。结果表明:在两种离子强度下,饱和吸附容量的增加顺序均为SCN-SO_4~(2-)HPO42-Cl~-;在低离子强度下,除SCN-外,反离子种类对传质速率和动态结合容量没有显著影响;在高离子强度下,传质速率的增加顺序为SCN-SO_4~(2-)≈Cl~-HPO42-,而动态结合容量的增加顺序与饱和吸附容量序列一致;两种离子强度下Cl~-均保持最高的动态结合容量;反离子种类对蛋白质洗脱行为没有显著影响。上述结果说明反离子主要影响FF-PEI-R440的吸附性能,而不影响洗脱,且流动相中选择Cl~-为反离子最利于FF-PEI-R440的实际柱色谱操作。     

减电荷聚甲基丙烯酸钠接枝介质的制备及蛋白质吸附性能

离子交换容量（IC）为320mmol/L的聚甲基丙烯酸钠（pMA）接枝型介质（FF-pMA-320）对溶菌酶和γ-球蛋白具有较高的吸附容量,但其传质速率较低。在保持聚合物链长度的前提下,通过乙醇胺与接枝链上的羧基进行电荷中和反应,降低pMA接枝型介质的电荷密度,提升介质的蛋白质传质速率。将FF-pMA-320进行部分电荷中和修饰,制备得到离子交换容量分别为230mmol/L和170mmol/L的减电荷阳离子交换介质,分别命名为pMA-320-R230和pMA-320-R170。采用吸附平衡、吸附动力学和柱穿透实验,研究了溶菌酶和γ-球蛋白在这两种新型介质上的吸附行为,并与初始介质FF-pMA-320进行了比较。结果表明：随着介质的IC值（电荷密度）从320mmol/L降低到170mmol/L,介质对两种蛋白质吸附容量随之减少,这与电荷中和修饰降低蛋白质吸附位点有关。随着接枝聚合物电荷密度的降低,相邻聚合物链之间的静电排斥作用减弱,蛋白质吸附容量降低,造成接枝链的灵活性增加以及蛋白质排阻效应减弱。因此,溶菌酶和γ-球蛋白在pMA-320-R170上的传质速率分别是FF-pMA-320的1...     

共聚物接枝蛋白离子交换色谱介质制备及性能

高容量蛋白质色谱介质是色谱过程高效化的材料基础和重要前提。采用原子转移自由基聚合（ATRP）技术,以甲基丙烯酸3-磺酸丙酯钾和甲基丙烯酸甲酯（MMA）为单体化合物合成了多种无规共聚物接枝离子交换色谱介质,并对其蛋白质吸附性能进行研究。单体总浓度一定情况下共聚物接枝色谱介质孔道半径（r_pore）随MMA浓度升高而增大,反映出接枝共聚物链渐趋塌陷的特征。蛋白质吸附结果表明,溶菌酶吸附容量取决于介质的离子交换容量;而抗体吸附容量则与rpore及相应的聚合物层厚度变化密切相关。随着聚合物层厚度的增大,聚合物层对抗体的空间排阻作用增强,抗体吸附容量下降。此外,引入MMA优化共聚物分子链可显著提高蛋白质吸附量,在SEP-gS30/M30介质中抗体和溶菌酶的饱和吸附量分别达到237 mg·g^-1和380 mg·g^-1。无规共聚物接枝离子交换色谱介质孔道内聚合物层厚度和蛋白质吸附也受无机盐浓度调控。     

接枝支链结构对聚乙烯多单体接枝共聚物结晶性能的影响

采用固相接枝法合成聚乙烯(PE)与甲基丙烯酸缩水甘油酯、苯乙烯、丙烯酸丁酯的固相接枝共聚物(PETM),利用差示扫描量热法、X射线衍射和偏光显微镜等测试手段研究了接枝支链对接枝共聚物的结晶过程的影响,并对接枝共聚物的X射线衍射峰进行分峰,计算接枝共聚物的晶胞参数。结果表明:接枝支链并没有改变PE的晶型,只是充当异相成核剂的作用并阻碍PE的晶体生长;受接枝支链影响,PE中存在不完善的结晶,PETM的结晶度比PE低。     

聚乙烯多单体接枝共聚物动态黏弹行为的研究

采用固相接枝法合成高密度聚乙烯(HDPE)与甲基丙烯酸缩水甘油酯(GMA)、苯乙烯(St)和丙烯酸丁酯(BA)的多单体接枝共聚物(PETM),并分析了接枝共聚物的结构和动态黏弹行为。结果表明,GMA,St,BA都参与了固相接枝反应,并接枝到HDPE主链。接枝支链对PETM有增塑作用。PETM中BA含量相对较多,柔性增加,弹性模量和损耗模量下降。HDPE接枝过程中容易产生凝胶物,引起损耗因子的增加。PETM中St含量增加,可以减少HDPE的交联反应和降低PETM中凝胶物含量,从而降低PETM的损耗因子。时温等效原理适合于描述PETM的动态力学行为。     

载体材料表面化学组成对蛋白质吸附行为的影响研究进展

蛋白质在载体表面的吸附行为,如其吸附速率、吸附量以及取向和构象的变化,在很大程度上依赖于载体材料的表面化学组成。调控载体材料的表面化学组成已成为控制蛋白质吸附行为的重要手段。本文主要对载体材料表面不同组成对蛋白质吸附行为的影响进行了归纳。介绍了材料表面的功能基团包括疏水基团（甲基和含氟基团）和亲水基团（羟基、氨基和羧基）对蛋白质吸附行为的影响。另外,在载体材料表面接枝聚合物链是一种常用的有效调控表面化学组成的方法。重点介绍了材料表面接枝不同聚合物链时,聚合物链的种类、长度、密度和链的结构对蛋白质吸附行为的影响。     

等离子接枝处理对高分子量聚乙烯纤维浸润性的影响

超高分子量聚乙烯纤维（UHMWPE纤维）经过苯乙烯和甲基丙烯酸低温等离子接枝处理后，通过观察悬挂在纤维上的乙二醇的液滴的形态，可计算纤维和液体表面的接触角；接触角的变小，说明纤维的浸润性能得到明显的改善。     

β成核剂对丙烯酸接枝聚丙烯结晶行为的影响

利用差示扫描量热仪(DSC)研究了一种聚丙烯常用的β成核剂(庚二酸/硬脂酸钙复合物)对聚丙烯接枝丙烯酸(PP-g-AA)的非等温结晶行为、结晶活化能、熔点和结晶度的影响。结果表明:添加β成核剂后,PP-g-AA的起始结晶温度明显提高,结晶活化能降低,这说明起到了异相成核的作用,而PP-g-AA的结晶速率下降。     

Lysozyme adsorption to cation exchanger derivatized by sequential modification of poly(ethylenimine)-Sepharose with succinic anhydride and ethanolamine: Effect of pH and ionic strength

In our previous work, a series of polyethylenimine(PEI)-derived cation exchangers were synthesized using PEIgrafted resin FF-PEI-L740(ionic capacity, 740 mmol·L~(-1)) as the basic resin to study lysozyme adsorption and chromatographic behavior. It was found that the resin with an ionic capacity of 630 mmol·L~(-1)(FF-PEI-CR630)possessed high adsorption performance towards lysozyme at 0–100 mmol·L~(-1) Na Cl. Therefore, in this work,FF-PEI-CR630 was selected to study the influences of pH and ionic strength(IS) on protein adsorption and chromatographic behavior towards lysozyme. The increase of lysozyme adsorption capacity in the pH range of 6 to 10 was observed. However, the uptake rate decreased in the pH range of 6 to 8 and then remained essentially unchanged from pH 8 to pH 10. Increasing IS led to decreased protein adsorption capacity and increased uptake rate in different pH ranges. Besides, FF-PEI-CR630 maintained dynamic binding capacity as high as over150 mg·ml~(-1) at pH 8–10 without NaCl. The research has thus provided insight into the selection of proper pH and IS conditions for protein purification by using FF-PEI-CR630.     

Influence of poly(acrylic acid) grafting density on switchable protein adsorption/desorption of poly(2-methyl-2-oxazoline)/poly(acrylic acid) mixed brushes

Poly(dopamine) is employed as an anchor to obtain a series of poly(acrylic acid) (PAA) and poly(2-methyl-2-oxazoline) (PMOXA) mixed brush coatings by sequential grafting to methods with PAA chains longer than PMOXA chains. Then, the prepared mixed brush coatings are rigorously characterized. The results show that the grafting density of PAA in mixed brushes could be well adjusted by changing the concentration of PAA solution used for the preparation of mixed brush coatings and the amounts of lysozyme adsorbed on PMOXA/PAA mixed brushes increase with increasing the grafting density of PAA chains while the desorption amounts decrease significantly when the grafting density of PAA is higher than one-half of PMOXA chains. When the grafting density of PAA is about one-half of PMOXA chains, the mixed brush could absorb high amounts of lysozyme (898.4 ng cm⁻²), and then more than 90% of adsorbed proteins could be released sharply by changing pH and ionic strength (I). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48135.     

Analysis of statistical thermodynamic model for binary protein adsorption equilibria on cation exchange adsorbent

A study of nonlinear competitive adsorption equilibria of proteins is of fundamental importance in understanding the behavior of preparative chromatographic separation. This work describes the nonlinear binary protein adsorption equilibria on ion exchangers by the statistical thermodynamic (ST) model. The single-component and binary protein adsorption isotherms of bovine hemoglobin (Hb) and bovine serum albumin (BSA) on SP Sepharose FF were determined by batch adsorption experiments in 0.05 mol/L sodium acetate buffer at three pH values (4.5, 5.0 and 5.5) and three NaCl concentrations (0.05, 0.10 and 0.15 mol/L) at pH 5.0. The ST model was found to depict the effects of pH and ionic strength on the single-component equilibria well, with model parameters depending on the pH and ionic strength. Moreover, the ST model gave acceptable fitting to the binary adsorption data with the fitted single-component model parameters, leading to the estimation of the binary ST model parameter. The effects of pH and ionic strength on the model parameters are reasonably interpreted by the electrostatic and thermodynamic theories. Results demonstrate the availability of the ST model for describing nonlinear competitive protein adsorption equilibria in the presence of two proteins.     

Effect of plasticizer on the crystallization behavior of poly(lactic acid)

In this article, the spherulitic morphology and growth rate of the neat and plasticized poly(lactic acid) (PLA) with triphenyl phosphate (TPP) were compared and analyzed by polarizing optical microscopy with hot stage at a temperature range of 100?142°C. The spherulitic morphology of the neat PLA underwent a series of changes such as the typical Maltese Cross at less than 132°C, the disappearance of the Maltese Cross at 133°C, the irregular and distorted spherulites at higher than 134 and 142°C, respectively. For plasticized PLA, the spherulitic morphology exhibited the same changes as neat PLA, but these changes were shifted to lower temperature when compared with neat PLA. In the case of the spherulitic growth, neat PLA had the maximum value of 0.28 μm/s at 132°C, and plasticized PLA had higher values than that of neat PLA. Further analysis based on the Lauritzen–Hoffman theory was presented and results showed that the values of nucleation parameter K_g increased with TPP content. The crystallization behavior of PLA was analyzed by differential scanning calorimetry and wide‐angle X‐ray diffraction. The results showed that the degree of crystallinity of plasticized PLA markedly increased when compared with neat PLA sharply with the incorporation of plasticizer. The crystallization kinetics for the neat and plasticized PLA under isothermal crystallization at 114°C was described by the Avrami equation and the Avrami exponent is close to 2, implying that the crystallization mechanism did not change. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies of adsorption of alkaline trypsin by poly(methacrylic acid) brushes on chitosan membranes

Poly(methacrylic acid)‐grafted chitosan membranes (chitosan‐g‐poly(MAA)) were prepared in two sequential steps: in the first step, chitosan membranes were prepared by phase‐inversion technique and then epichlorohydrin was used as crosslinking agent to increase its chemical stability in acidic media; in the second step, the graftcopolymerization of methacrylic acid onto the chitosan membranes was initiated by ammonium persulfate (APS) under nitrogen atmosphere. The chitosan‐g‐poly(MAA) membranes were first used as an ion‐exchange support for adsorption of trypsin from aqueous solution. The influence of pH, equilibrium time, ionic strength, and initial trypsin concentration on the adsorption capacity of the chitosan‐g‐poly(MAA) membranes have been investigated in a batch system. Maximum trypsin adsorption onto chitosan‐g‐poly(MAA) membrane was found to be 92.86 mg mL^?1 at pH 7.0. The experimental equilibrium data obtained for trypsin adsorption onto chitosan‐g‐poly(MAA) membranes fitted well to the Langmuir isotherm model. The adsorption data was analyzed using the first‐ and second‐order kinetic models, and the experimental data was well described by the second‐order equation. More than 97% of the adsorbed trypsin was desorbed using glutamic acid solution (0.5M, pH 4.0). In addition, the chitosan‐g‐ poly(MAA) membrane prepared in this work showed promising potential for various biotechnological applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Physicochemical investigation of radiation‐grafted poly(acrylic acid)‐graft‐poly(tetrafluoroethylene–ethylene) copolymer membranes and their use in metal recovery from aqueous solution

ET‐g‐PAAc membranes were obtained by radiation grafting of acrylic acid onto poly(tetrafluoroethylene–ethylene) copolymer films using a mutual technique. The ion selectivity of the grafted membranes was determined toward K⁺, Ag⁺, Hg²⁺, Co²⁺, and Cu²⁺ in a mixed aqueous solution. The ion‐exchange capacity of the grafted membranes was measured by back titration and atomic absorption spectroscopy. The Hg²⁺ ion content of the membrane was more than that of either the K⁺ or Ag⁺ ions. The presence of metal ions in the membranes was studied by infrared and energy‐dispersive spectroscopy measurements. Scanning electron microscopy of the grafted and metal‐treated grafted membranes showed modification of the morphology of the surface due to the adsorption of K⁺ and Ag⁺ ions. No change was observed for the surface of the membrane that was treated with Hg²⁺ ions. The thermal stability of different membranes was improved more with Ag⁺ and Hg²⁺ ions than with K⁺ ions. It was found that the modified grafted membranes possessed good hydrophilicity, which may make them promising candidates for practical applications, such as for cation‐exchange membranes in the recovery of metals from an aqueous solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2692–2698, 2002     

Blood protein adsorption onto macroporous semi‐interpenetrating polymer networks (IPNs) of poly(ethylene glycol) (PEG) and poly(2‐hydroxyethyl methacrylate) (PHEMA) and assessment of in vitro blood compatibility

This work reports a study of the adsorption of fibrinogen (Fgn) onto the surface of semi‐interpenetrating polymer networks (IPNs) of poly(ethylene glycol) (PEG) and poly(2‐hydroxyethyl methacrylate) (PHEMA). The semi‐IPNs were prepared by polymerizing 2‐hydroxyethyl methacrylate with a redox system and in the presence of PEG and crosslinker ethyleneglycol dimethacrylate. The proposed spongy IPNs were characterized by Fourier transform infrared and environmental scanning electron microscopy methods, and network structural parameters, such as molecular weight between crosslinks and crosslink density, were calculated using swelling measurements. The adsorption of Fgn was carried out onto the spongy IPNs and kinetic constants of the adsorption process as well as isotherm constants were evaluated. The adsorption process was also studied under varying pH, ionic strengths, and chemical architecture of the IPNs. The anti‐thrombogenic behaviour of the polymer matrices was judged using in vitro tests. Copyright © 2006 Society of Chemical Industry     

Surface DEAE groups facilitate protein transport on polymer chains in DEAE‐modified‐and‐DEAE‐dextran‐grafted resins

Sepharose FF was modified with diethylaminoethyl‐dextran (DEAE‐dextran, DexD) and/or DEAE (D) to fabricate three types of ion exchangers FF‐DexD (grafting‐ligand resin), FF‐D (surface‐ligand resin), and FF‐D‐DexD (mixed‐ligand resin), for protein adsorption equilibria and kinetics study. It was found that both adsorption capacity and uptake rate (effective diffusivity, D_e) were significantly enhanced by grafting DEAE‐dextran. Notably, the D_e values on FF‐DexD and FF‐D‐DexD (D_e/D₀ > 1.4) were six times greater than those on FF‐D (D_e/D₀ < 0.3). More importantly, the increase of surface‐ligand density greatly enhanced uptake kinetics on FF‐D‐DexD. The results indicate that the surface ligands assisted the transport of bound proteins on polymer chains in the mixed‐ligand resins. That is, surface ligands worked as “transfer stations” between two neighboring chains, resulting in enhanced transport of bound proteins on chains. The research thus disclosed the unique role of surface ligands in facilitating protein uptake kinetics onto polymer‐grafted ion‐exchangers. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3812–3819, 2016