谷胱甘肽键合柱对蛋白的选择性研究

通过将谷胱甘肽键合到硅胶表面合成了同时具有弱阳离子交换(WCX)、疏水(HIC)和氢键作用的多功能色谱填料, 该固定相在HIC和WCX模式下对蛋白都有很好的分离效果. 实验通过计量置换保留模型对蛋白在谷胱甘肽键合柱上的色谱保留行为及机理进行了研究, 结果发现, 在流动相盐浓度较低时蛋白根据自身等电点高低通过静电作用力得以分离, 而在高盐浓度下疏水和氢键作用力共同决定蛋白的保留. 这种多作用力保留模式可有效提高色谱柱的选择性, 尤其为蛋白质、多肽及氨基酸的高效分离提供新的解决思路.     

关于混合模式色谱固定相对蛋白保留特征的研究

为使混合机理色谱(MMC)得到广泛地应用, 合成、表征和评价MMC固定相就成了首先要解决的问题. 依据离子交换色谱柱也具有疏水色谱(HIC)保留机理的特征, 选了4种弱阳离子交换(WCX)柱和一根二维[2D(WCX,HIC)]色谱柱, 研究了标准蛋白在这两类色谱柱上的保留行为. 这四种WCX色谱柱中的两种能在WCX和HIC两种分离模式下分离蛋白, 虽不如2D色谱柱效果好, 但有可能当成“准2D柱”来使用. 发现蛋白在这四种WCX柱上所显示的HIC分离特征各不相同, 且保留值随盐浓度变化呈现出的“U型”曲线也有大的差异. 实验结果显示, “U型”曲线的宽度和临界点分别与色谱动力学和热力学因素相关. 还对这两类色谱固定相的峰容量表征方法和命名提出了建议和说明.     

氨基己酸为配基的新型弱阳离子交换/疏水双功能色谱固定相对蛋白质的分离纯化

以硅胶为基质、氨基己酸为配基制备了一种新型弱阳离子交换/疏水（WCX/HIC）双功能混合模式色谱固定相。该固定相配基具有一定的疏水性且含有羧基,在高盐浓度下表现为HIC的性质,可作为HIC固定相使用;在低盐浓度条件下表现为离子交换的性质,可作为WCX固定相使用。分别考察了该介质在WCX和HIC两种模式下对标准蛋白质的分离性能,并与商品柱进行比较。结果表明,所合成的WCX/HIC双功能固定相在WCX和HIC两种模式下对蛋白质均有较高的分离度和选择性,且分离能力与商品柱相当,两种模式下标准蛋白质的质量和活性回收率均大于93%,表明该柱具有“一柱二用”的功能,适于生物大分子的分离纯化。基于此双功能色谱柱构建的在线单柱二维液相色谱（2DLC-1C）可在60 min内实现8种蛋白质的快速分离。在70 min内完成了对蛋清中溶菌酶的二维纯化,纯度可达到98.3%。该技术中一根色谱柱可当作两根色谱柱使用,对蛋白质组学研究和重组蛋白药物的生产具有重要的应用价值。     

动力学因素对液相色谱分离整体蛋白的影响

依据液相色谱分离整体蛋白的效果与色谱柱柱长基本无关的事实,研究了动力学因素对疏水相互作用色谱(HIC)分离整体蛋白的影响。首次提出了用于线性梯度洗脱条件下蛋白分离的“条件板高”(H)概念,并将其用于动力学因素对分离整体蛋白的影响的表征。分别用常用的色谱柱和色谱饼对标准蛋白进行了分离,绘制了类似于van Deemter的“条件板高”对流动相线速(u)的曲线图。发现对应于色谱柱最低“条件板高”的适合线速约为色谱饼的1/5～1/15,且色谱饼的适合线速范围也较色谱柱宽得多。据此,用装填有HIC填料的色谱饼(10 mm×20 mm i.d.)在12 min内便可完全分离7种标准蛋白。还用装填有HIC填料的色谱饼对重组人粒细胞集落刺激因子(rhG-CSF)进行了复性并同时纯化,在50 min内,仅用一步色谱法就可获得纯度≥97%的rhG-CSF,其质量回收率为39%,比活＞1×108 IU/mg。可以预计,装填极细颗粒的刚性色谱填料的色谱饼可在高负荷条件下进行整体蛋白的高速和高分离度的分离、纯化并同时复性,达到“三高”。     

用芳香醇同系物研究疏水色谱的保留机理

首次研究了芳香醇同系物在疏水色谱（HIC）中的保留行为。同系物的保留符合同系物规律。随绝对温度倒数的增加，保留值先增大而后减小，符合Van‘t Hoff曲线方程。用计量置换保留模型中的参数表征了同系物分子的性质，揭示了HIC中小分子的保留在本质上与反相色谱相同，均由非选择性疏水作用力所控制。证明了用中性小分子作为溶质研究HIC保留机理是一个新方法，为研究生物大分子在疏水色谱中的保留机理奠定了基础。     

两种带有不同间隔臂的环糊精键合固定相保留行为的评价

选取14种模型化合物对两种带有不同间隔臂的环糊精键合固定相(Click Alkyl-CD、Click OEG-CD)进行了反相液相色谱模式下的保留行为评价。通过梯度洗脱条件下保留参数计算方法和CSASS软件,根据3次线性梯度的保留值数据,测出14种溶质分子在两种固定相上的保留参数,在此基础上考察流动相含乙腈浓度与保留因子的关系后发现,Click Alkyl-CD和Click OEG-CD在分离非极性和中等极性化合物时主要基于反相液相色谱模式,而某些化合物(如吲唑)在Click OEG-CD上的保留受多种作用力影响,并不基于反相液相色谱模式。疏水性评价结果表明,反相分离模式下Click Alkyl-CD的保留参数和正辛醇-水分配常数的相关性较好(R=0.7),说明其具有比较强的疏水性;而Click OEG-CD的相关性不高(R＜0.3),说明疏水作用力以外的其他作用力对化合物在反相模式下的保留影响较大。     

厚朴酚键合硅胶高效液相色谱固定相分离嘌呤、嘧啶、蝶呤及黄酮

将新制备的厚朴酚键合硅胶固定相(MSP)用于嘌呤、嘧啶、蝶呤及黄酮类化合物的液相色谱分离分析。选取了4种嘌呤、8种嘧啶、4种蝶呤及5种黄酮类药物作为极性化合物的代表,以商品反相碳十八烷基键合硅胶柱(ODS)作参照,研究了新固定相对碱性化合物的选择性和相关分离机理。实验发现,在简单流动相条件下,厚朴酚键合硅胶固定相对上述药物表现出较高的选择性及分离效果。尽管MSP没有进行封尾处理,但含氮类极性化合物(嘌呤、嘧啶、蝶呤)仍表现出基本对称的色谱峰形。多数药物在两柱上的洗脱顺序大致相同,说明疏水作用始终存在,这说明新固定相具有反相色谱性能。比较研究还发现,MSP在分离上述极性药物时能够提供除疏水性作用之外的其他作用位点。例如,在分离嘌呤、嘧啶及蝶呤时,氢键和偶极作用明显存在;同时MSP与溶质结构中的芳环(硫唑嘌呤、紫花牡荆素)之间有较强的π-π电子相互作用等,使得含氮类极性化合物和黄酮的保留一般比ODS强,分离度也有一定的改善。多种作用可以合理地解释MSP柱对极性溶质有更强的分离能力,厚朴酚键合硅胶固定相可在一定程度上弥补ODS单一疏水作用的不足,有利于分类碱性化合物。     

基于二醛微晶纤维素功能化C18的反相/亲水色谱固定相的制备

通过十八烷基胺的氨基与二醛微晶纤维素的醛基共价键合,制备了基于二醛微晶纤维素(DMCC)官能化C₁₈的新型反相/亲水色谱固定相(C₁₈-DMCC/SiO₂),该色谱固定相被用于反相色谱(RPLC)和亲水相互作用色谱(HILIC)模式。C₁₈-DMCC/SiO₂色谱柱展现了良好的疏水选择性和芳香选择性,在反相色谱模式下可分离烷基苯和多环芳烃(PAHs)。苯胺类、酚类和糖苷类等极性化合物被用于评估该色谱柱在反相色谱模式下的极性选择性,商品C₁₈柱作对照柱,色谱评价结果令人满意。核酸碱基被用于评估C₁₈-DMCC/SiO₂色谱柱的亲水色谱性能。通过考察有机溶剂含量对分析物保留的影响,发现该新型色谱固定相具有反相/亲水色谱的典型特征。     

31ku激发子蛋白的液相色谱分离纯化

利用阴离子交换色谱和疏水相互作用色谱从烟草疫霉菌培养液中分离出一种新的31ku激发子蛋白，选择了阴离子交换色谱流动相的的最佳pH值6．0，建立了疏水相互作用色谱硫酸铵Tris缓冲液－水洗脱模式，简化了纯化步骤和减少了活性损失的危险。     

疏水作用色谱中流动相组成对溶质保留行为的影响

 首次研究了疏水作用色谱 (HIC)中芳香醇同系物在不同种类盐流动相中的保留行为。以计量置换保留模型中的参数Z分析了HIC中小分子与生物大分子保留行为的差别 ,以及不同流动相组成对两种类型溶质的洗脱范围及洗脱能力的影响。与反相色谱相似 ,芳香醇在HIC中的保留仍存在同系物规律。比较了小分子和生物大分子在不同盐溶液中的Z值变化 ,表明流动相中的盐仅改变小分子与固定相的水合程度 ,而对生物大分子 ,除改变其和固定相水合程度外 ,还会影响生物大分子与固定相接触区的分子构象     

Preparation and characterization of a novel dual‐retention mechanism mixed‐mode stationary phase with PEG 400 and succinic anhydride as ligand for protein separation in WCX and HIC modes

A novel dual‐retention mechanism mixed‐mode stationary phase based on silica gel functionalized with PEG 400 and succinic anhydride as the ligand was prepared and characterized by infrared spectra and elemental analysis. Because of the ligand containing PEG 400 and carboxyl function groups, it displayed hydrophobic interaction chromatography (HIC) characteristic in a high‐salt‐concentration mobile phase, and weak cation exchange chromatography (WCX) characteristic in a low‐salt‐concentration mobile phase. As a result, it can be employed to separate proteins with both WCX and HIC modes. The resolution and selectivity of the stationary phase was evaluated under both HIC and WCX modes with protein standards, and its performance was comparable to that of conventional ion‐exchange chromatography and HIC columns. The results indicated that the novel dual‐retention mechanism column, in many cases, could replace two individual WCX and HIC columns as a ‘2D column’. In addition, the mixed retention mechanism of proteins on this ‘2D column’ was investigated with stoichiometric displacement theory for retention of solute in liquid chromatography in detail in order to understand why the dual‐retention mechanism column has high resolution and selectivity for protein separation under WCX and HIC modes, respectively. Based on this ‘2D column’, a new 2DLC technology with a single column was developed. It is very important in proteome research and recombinant protein drug production to save column expense and simplify the processes in biotechnology. Copyright © 2013 John Wiley & Sons, Ltd.     

Weak anion and cation exchange mixed-bed microcolumn for protein separation

To separate proteins with a wide distribution of pIs under the conditions compatible to online tryptic digestion (with preferable pH=8.0), weak anion and cation exchange chromatography (WAX/WCX) mixed‐bed microcolumn has been developed. With a mixture of five proteins with pIs ranging from 4.2 to 11.4, the effect of WAX/WCX ratio on the separation performance was investigated, and an optimum packing ratio of 1:1 w/w was obtained. Moreover, the undesirable hydrophobic interaction between the proteins and the stationary phase was suppressed with 10% ACN v/v added in the mobile phases. Under the optimized conditions compatible to tryptic digestion, basic and acidic proteins were resolved simultaneously, with RSDs of relative retention time on six columns less than 6%, indicating the good resolution and packing reproducibility. Furthermore, one RPLC fraction of proteins extracted from rat middle brain and the whole protein mixture extracted from rat liver were analyzed, respectively. The results demonstrated better separation performance on WAX/WCX microcolumns than that on both weak anion exchange chromatography and weak cation exchange chromatography at pH ～8. We anticipate that WAX/WCX microcolumns are promising for the integration of protein separation and tryptic digestion aiming at high‐throughput proteome study.     

Mixed retention mechanism of proteins in weak anion-exchange chromatography

Using four commercial weak anion-exchange chromatography (WAX) columns and 11 kinds of different proteins, we experimentally examined the involvement of hydrophobic interaction chromatography (HIC) mechanism in protein retention on the WAX columns. The HIC mechanism was found to operate in all four WAX columns, and each of these columns had a better resolution in the HIC mode than in the corresponding WAX mode. Detailed analysis of the molecular interactions in a chromatographic system indicated that it is impossible to completely eliminate hydrophobic interactions from a WAX column. Based on these results, it may be possible to employ a single WAX column for protein separation by exploiting mixed modes (WAX and HIC) of retention. The stoichiometric displacement theory and two linear plots were used to show that mechanism of the mixed modes of retention in the system was a combination of two kinds of interactions, i.e., nonselective interactions in the HIC mode and selective interactions in the IEC mode. The obtained U-shaped elution curve of proteins could be distinguished into four different ranges of salt concentration, which also represent four retention regions.     

“Click chemistry” preparation of WCX packings for protein separation

Click chemistry was applied to immobilize three kinds of alkyne-carboxylic acids onto azide-modified silica gel to prepare three novel stationary phases for weak cation exchange chromatography(WCX).The developed protocol combines the benefits of operational simplicity,exceptionally mild conditions and high surface loadings.Six kinds of standard proteins were separated completely on the novel packings.Compared with commercial WCX columns,the three kinds of novel WCX packings prepared by click chemistry approach have better resolution and selectivity.Lysozyme was purified successfully from egg white with the novel WCX column by one step.The purity was more than 97%and a high specific activity was achieved to be 81,435 U/mg.The results illustrate the potential of click chemistry for preparation of stationary phase for IEC.     

Preparation of poly(vinyltetrazole) chain-grafted poly(glycidymethacrylate-co-ethylenedimethacrylate) beads by surface-initiated atom transfer radical polymerization for the use in weak cation exchange and hydrophilic interaction chromatography

A novel stationary phase for weak cation exchange (WCX) and hydrophilic interaction chromatography (HILIC) was prepared with surface-initiated atom transfer radical polymerization (SI-ATRP). Vinyltetrazole was grafted onto the surface of the beads in water medium with the polyglycidylmethacrylate beads (P_GMA/EDMA) previously modified with 2-bromoisobutryl bromide as the macromolecule initiators and CuCl as catalyst. The poly(vinyltetrazole)-grafted beads obtained with different atom transfer radical polymerization (ATRP) formulations were tried as chromatographic packings in ion-exchange chromatography. The results showed that the prepared columns could separate the tested proteins with high efficiency and high capacity, and the retention time of protein had a positive relationship with increasing the chain lengths of the grafted poly(vinyltetrazole) (PVT). The prepared column was also found to be able to separate nucleosides by hydrophilic interaction chromatographic mode.     

Comparison and evaluation of HIC columns of different hydrophobicity

Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log k_w values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (k_g) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Effect of surface hydrophobicity distribution on retention of ribonucleases in hydrophobic interaction chromatography

The effect of surface hydrophobicity distribution of proteins on retention in hydrophobic interaction chromatography (HIC) was investigated. Average surface hydrophobicity as well as hydrophobic contact area between protein and matrix were estimated using a classical thermodynamic model. The applicability of the model to predict protein retention in HIC was investigated on ribonucleases with similar average surface hydrophobicity but different surface hydrophobicity distribution. It was shown experimentally that surface hydrophobicity distribution could have an important effect on protein retention in HIC. The parameter "hydrophobic contact area," which comes from the thermodynamic model, was able to represent well the protein retention in HIC with salt gradient elution. Location and size of the hydrophobic patches can therefore have an important effect on protein retention in HIC, and the hydrophobic contact area adequately describes this.     

亲水作用色谱柱与阳离子交换树脂柱结合分离无机离子（英文）

A combination of hydrophilic interaction chromatographic(HILIC) column and a weakly acidic cation-exchange resin(WCX) column was used for simultaneous separation of inorganic anions and cations by ion chromatography(IC).Firstly,the capability of HILIC column for the separation of analyte ions was evaluated under acidic eluent conditions.The columns used were SeQuant ZIC-HILIC(ZIC-HILIC) with a sulfobetaine-zwitterion stationary phase(ZIC-HILIC) and Acclaim HILIC-10 with a diol stationary phase(HILIC-10).When using tartaric acid as the eluent,the HILIC columns indicated strong retentions for anions,based on ion-pair interaction.Especially,HILIC-10 could strongly retain anions compared with ZIC-HILIC.The selectivity for analyte anions of HILIC-10 with 5 mmol/L tartaric acid eluent was in the order of I-> NO-3 > Br-> Cl-> H2PO-4.However,since HILIC-10 could not separate analyte cations,a WCX column(TSKgel Super IC-A/C) was connected after the HILIC column in series.The combination column system of HILIC and WCX columns could successfully separate ten ions(Na+,NH+4,K+,Mg2+,Ca2+,H2PO-4,Cl-,Br-,NO-3 and I-) with elution of 4 mmol/L tartaric acid plus 8 mmol/L 18-crown-6.The relative standard deviations(RSDs) of analyte ions by the system were in the ranges of 0.02%-0.05% in retention times and 0.18%-5.3% in peak areas through three-time successive injections.The limits of detection at signal-to-noise ratio of 3 were 0.24-0.30 μmol/L for the cations and 0.31-1.2 μmol/L for the anions.This system was applied for the simultaneous determination of the cations and the anions in a vegetable juice sample with satisfactory results.