Protein retention in dextran-grafted cation exchange chromatography:The influence of pHs,counterions and polymer structure

Polymer-grafted ion exchange adsorbents were of great interest for the development of high-performance protein chromatography in biopharmaceutical and related fields.In this work,protein retention was systematically investigated in ion exchange chromatography packed respectively with dextran-grafted cation exchange adsorbents containing sulphopropyl(SP)ligand,SP Sepharose XL and Capto S,and non-grafted cation exchange adsorbent,SP Sepharose FF,using five proteins.With an increase of buffer p Hs,retention factors of proteins decreased among all the adsorbents,demonstrating the dominant role of electrostatic interaction for protein binding on cation exchange adsorbents.The evidences further revealed that the scattered positive charges on the surface of protein molecules,rather than net charge of protein molecule,determined protein retention on cation exchange adsorbent.Likely,counterions including NH4^+,K^+,Na^+and Mg^2+exhibited distinct influence on protein retention.It was well ascribed to solvent-mediated indirect ion-macromolecule interactions and direct ion-macromolecule interactions.Compared with SP Sepharose FF,polymer structure in dextran-grafted cation exchange adsorbents ultimately brought about different ligand distributions and smaller pore sizes,thereby regulating protein retention in cation exchange chromatography.By comparing the retention of myoglobin andβ-lactoglobulin B in SP Sepharose XL and Capto S,we reasonably speculated that the enhancement of nonelectrostatic interaction caused by reducing the space arm length was a major reason for an increasing retention factor of myoglobin in Capto S.The results in this research help us understand adsorption mechanism of protein in polymer-grafted adsorbents and give scientific guidance for the development of chromatographic materials.

Possible Magnetic Resonance Signal Due to the Movement of Counterions around a Polyelectrolyte with Rotational Symmetry

Experimental, theoretical and computational studies revealed that the characteristic time scales involved in counterion dynamics in polyelectrolytes systems might span several orders of magnitude ranging from subnanosecond times to time scales corresponding to acoustic-like phonon mode frequencies, with an structural organization of counterions in charge density waves (CDWs). These facts raise the possibility of observing Magnetic Resonance (MR) signals due to the movement of counterions in polyelectrolytes. In case that this signal is detected in macroions or other biological systems, like micelles, vesicles, organeles, etc. with rotational symmetry, this method opens a new tool to measure with precission the counterions velocity.

Chiral Recognition of Binaphthyl Derivatives with L-Undecyl Leucine Surfactants in the Presence of Sodium and Lysine Counterions

This study investigates the effect of counterions on the chiral recognition of 1,1'-Binaphthyl-2,2'-diamine (BNA) and 1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate (BNP) enantiomers when using an amino acid-based surfactant undecanoyl L-leucine (und-Leu) as the chiral pseudostationary phase in capillary electrophoresis. The effects of using two different counterions (sodium and lysine) on the chiral recognition of binaphthyl derivatives were compared at varying pH conditions. The enantiomeric separation of BNA and BNP enantiomers via capillary electrophoresis, using und-Leu as the chiral recognition medium, significantly improved the enantiomeric resolution in capillary electrophoresis at pH 7 when using Lysine counterions as compared to using sodium as the counterion. More specifically, at a surfactant concentration of 45 mM, at pH 7, a significant increase in chiral selectivity was observed when lysine was used as the counterion compared to sodium. The enantiomeric resolution of BNA and BNP increased by 6-fold and 1.1-fold, respectively, in capillary electrophoresis experiments when lysine was utilized as the counterion compared to using sodium. Furthermore, the retention factor of BNA and BNP enantiomers also increased approximately 3.5-fold and 4-fold, respectively, in the presence of lysine counterions as compared to using sodium counterions. When running buffer in capillary electrophoresis was increased to pH 11, the resolution and retention factors were nearly identical when comparing the effects of the sodium and lysine counterions. This signifies the important role of lysine’s positive net charge on chiral recognition. This study provides insight into the potential advantages of using cationic, pH-dependent counterions such as lysine to significantly improve the chiral recognition of binaphthyl derivatives when using chiral anionic surfactants as the pseudostationary phase in capillary electrophoresis.

Counterion Binding in Aqueous Solutions of Poly(vinylpyridines) as Assessed by Potentiometric Titration

The extent to which counterions bind to polyelectrolytes influences a variety of polymer-based applications, including polyelectrolyte enhanced ultrafiltration and forward osmosis using polyelectrolytes as draw agents. Potentiometric titrations of poly (2-vinylpyridine) (P2VP), poly (3-vinylpyridine) (P3VP), and poly (4-vinylpydine) (P4VP) were performed using HBr, HCl, HNO3, and HClO4 in both the presence and absence of added NaCl. Because of the systematic differences among the three polyelectrolytes, titration results provide insight into the role of polymer structure in the relative extents to which various counterions bind. Titration data reveal that ionization properties vary as functions of polymer investigated, titrant used, degree of protonation, and added salt concentration. Acid dissociation constants of the pyridinium moieties were found to generally increase with increasing degree of protonation, though appreciable differences were exhibited among the three polymers investigated. For all three polymers, Cl- demonstrated the lowest affinity for the charged pyridinium residues, while the affinities associated with Br- and NO-3 were nearly identical to each other. The relative extent of binding for CIO-4 varied across the polymers investigated, and was greatest for P4VP.

Counterion-Mediated Hydrogen Bonding Making Strong Polyelectrolytes pH-Responsive:Current Understanding and Perspectives

The counterion-mediated hydrogen bonding(CMHB)is related to the hydrogen bonding between bound counterions and polyelectrolyte chains in polyelectrolyte systems,where the counterions can both electrostatically bind to the charged groups of polyelectrolyte chains and act as hydrogen bond donors or acceptors to form hydrogen bonds with the hydrogen bond sites associated with polyelectrolyte chains simultaneously.A large number of literatures illustrate that strong polyelectrolytes(SPs)are insensitive to pH,which severely limmits the applications of SPs as smart materials.However,our studies have demonstrated that the CMHB makes SPs pH-responsive.This perspective discusses the mechanism of pH responsiveness of SPs and the pH-tunable properties of SPs,based on the pH-controlled CMHB effect.The future research directions on the pH responsiveness of SPs are also discussed here.It is anticipated that the study of the pH responsiveness of SPs not only will provide a new understanding of the fundamental properties of SPs,but also will greatly expand the applications of SPs in the field of smart materials.

Tuning the local coordination environment of silver(Ⅰ) coordination networks with counterions for enhanced electrocatalytic CO_(2) reduction

Very recently, the local coordination environment of active sites has been found to strongly influence their performance in electrocatalytic CO_(2) reduction by tuning the intrinsic kinetics of CO_(2) activation and intermediate stabilization. It is imperative to elucidate the mechanism for such an influence towards the rational design of efficient catalysts;however, the complex interactions between the multiple factors involved in the system make it challenging to establish a clear structure–performance relationship. In this work, we chose ion-intercalated silver(I)-based coordination networks(AgCNs) with a well-defined structure as a model platform, which enables us to understand the regulation mechanism of counterions as the counterions are the only tuning factor involved in such a system. We prepared two isostructural Ag CNs with different intercalation ions or counterions of BF_(4)^(-) and ClO_(4)^(-)(named as AgCNs-BF_(4) and AgCNs-ClO_(4)) and found that the former has a more competitive CO_(2) electroreduction performance than the latter. AgCNs-BF_(4) achieves the highest Faradaic efficiency for CO_(2) to CO of 87.1% at-1.0 V(vs. RHE) with a higher partial current density, while AgCNs-ClO_(4) exhibits only 77.2% at the same applied potential.Spectroscopic characterizations and theoretical calculation reveal that the presence of BF_(4)^(-)is more favorable for stabilizing the COOH^(*) intermediate by weakening hydrogen bonds, which accounts for the superior activity of Ag CNs-BF_(4).

Effect of Variant Counterions on Stability and Particle Size of Silica Sol

The effects of variant counterions with ionic strength of 0.05, 0.10, 0.20 and 0.25 mol·kg^-1 on the stability and particle size of silica sols have been studied using the traditional methods of Ubbelohde viscosity measurement, TEM and titration respectively, finding that the stability and particle size of the silica sols are all concerned with the acidic, positively electric properties and the sizes of the counterions, as well as the attraction between the counterions and surface silicon hydroxyl groups of the silica sols. The small positively charged counterions lead to the decrease in particle sizes, making the silica sol the most stable. But the larger weakly acidic counterions can restrict the particle sizes of the silica sols and easily make the sols coagulate. It was also found that there existed a linear relationship between log r and log η, which has not ever been reported. The effect of temperature on the stability and particle sizes was also discussed.

A Novel Fluorescent Probe for ATP Detection Based on Synergetic Effect of Aggregation-induced Emission and Counterion Displacement

In this work,a fluorescent probe(TPEBe-I)was developed for adenosine triphosphate(ATP)detection based on the synergetic effect of aggregation-induced emission and counterion displacement.TPEBe-I gave weak emission in aqueous solution due to the heavy-atom effect of counter iodide ion.However,upon the addition of ATP,the new aggregate complex(TPEBe-ATP)was formed between the cationic unit of TPEBe-I and ATP through electrostatic interactions,which not only restricted the intramolecular motion of luminogen but also eliminated the quenching effect of iodide ion.As a result,the fluorescent light-up detection for ATP was successfully achieved.Moreover,TPEBe-I exhibited high selectivity towards ATP and showed a wide linear detection region towards the logarithm of ATP concentration(5—600µmol/L)with a detection limit of 1.0µmol/L,enabling TPEBe-I as a promising probe for ATP quantitative analysis.

Effect of Alkylpyrazinium Counterions on the Host-guest Recognition Based on Dimethoxypillar[5]arenes

In this work, we synthesized n-octylpyrazinium bromide（G-Br） and n-octylpyrazinium hexafluorophos- phate（G-PE6） as model guests and studied their host-guest complexation with 1,4-dimethoxypillar[5]arene（DMP5A）. Effect of alkylpyrazinium counterions on the host-guest recognition was investigated. Based on the lH NOESY spectra, the binding site of DMP5A with G-PF6 is the same as that of DMP5A with G-Br. However, G-PF6 forms a stronger complex with DMP5A than G-Br, owing to that hexafluorophosphate forms weaker doubly inonic H-bonds with ammonium cation than bromide ion in chloroform, which leads to some aggregates that could be dissociated with the addition of DMP5A.

Conformational Behavior of Single Circular Semiflexible Polyelectrolyte in the Presence of Multivalent Counterions

Langevin dynamics simulations are employed to explore the effects of chain stiffness and electrostatic interaction(EI) on the conformational behavior of a circular semiflexible polyelectrolyte(CSPE) in presence of trivalent counterions.We investigate the effect of bending energy b and the dimensionless Bjerrum length A on the conformational behavior of the CSPE with a fixed chain length.The competition among the EIs,chain stiffness and entropy of the system leads to rich conformations for the CSPE.As the b is less than or equal to 50,The shape of the CSPE changes from a oblate ring to a rod at small A,then to a toroid at intermediate A,and finally to a globule at very large A.However,the globular conformation is not observed for large b.In addition,we find that the number of torus ring increases with A increase,while decreases with b increase.This study should be helpful in gaining insight into the conformational behaviour of charged biopolymer.

前沿科研成果融入分析化学实验教学——高亮度荧光聚合物纳米颗粒的合成及表征

荧光纳米颗粒在生物成像、传感和诊断等领域展现了广阔的应用前景。然而,传统的有机染料常受到聚集导致荧光猝灭效应的限制。本文以自组装聚合物纳米颗粒的制备和表征为例,将反离子增强荧光策略引入分析化学实验教学,为学生提供了一种新型荧光增强方法的实践体验。通过这一实验,学生能够掌握聚合物纳米颗粒的合成、表征技术及反离子增强荧光发射的原理,深入理解荧光聚集导致猝灭效应及其解决方法。该实验设计不仅有效提升了学生对分析化学知识的理解和应用能力,还拓展了其对纳米材料科学的认知,为未来在相关领域的研究奠定了坚实基础。

κ-卡拉胶研究进展

结合作者的研究工作 ,综述了κ 卡拉胶 (KC)的化学结构、性质。

κ-卡拉胶热可逆凝胶化行为研究

用固体小角激光散射方法研究κ 卡拉胶 (KC)的热可逆凝胶化行为 .以散色斑点的突停点温度为体系的凝胶化点Tgel,考察了溶液中加入Na+ ,K+ ,NH+4,Ca2 + ,Cu2 + ,Zn2 + 等抗衡离子对Tgel的影响 .结果是随抗衡离子浓度增大Tgel上升 ;Tgel与Na+ 的浓度呈线性关系 ,与K+ ,NH+4,Ca2 + ,Cu2 + ,Zn2 + 等离子浓度的平方根成线性关系 ;另外 ,还得到 30℃时KC在KCl盐溶液中的溶胶 凝胶相图 ,并对比了KC在NaCl溶液中透析前后Tgel的变化 .

反离子对氟表面活性剂的影响1.表面活性及胶团化作用

通过表面张力和荧光探针法研究了全氟辛酸钠、全氟辛酸铵以及全氟辛酸四烷基铵[C7F15COON(CnH2n+14),n=1,2,3,4]的表面活性以及胶团化作用,系统地讨论了各种反离子,特别是反离子大小的影响.结果表明,与普通碳氢表面活性剂不同,反离子对这类氟表面活性剂的表面活性以及胶团化作用有很大影响.表面活性剂的临界胶束浓度(cmc)随反离子的增大而下降;饱和吸附层中平均每个分子所占的面积则大致随反离子的增大而增大.而表面张力的变化则较为复杂.cmc时的表面张力随反离子的增大先上升(从全氟辛酸铵到全氟辛酸四乙铵)后下降(从全氟辛酸四乙铵到全氟辛酸四丁铵).通过反离子的空间位阻、疏水性、插入以及电荷屏蔽效应对上述结果做了解释.

全氟辛酸、全氟辛基磺酸乙醇胺盐表面活性剂的性质研究

通过测试表面张力、泡沫性质与粘度性质,研究全氟辛酸乙醇铵/二乙醇铵/三乙醇铵和全氟辛基磺酸乙醇铵/二乙醇铵/三乙醇铵的性质。实验表明,反离子对全氟辛酸盐和全氟辛基磺酸盐表现出相同规律的影响,这种影响体现在反离子的疏水性和空间体积两个方面,分别导致了cmc顺序:乙醇铵>二乙醇铵>三乙醇铵,以及与之相反的γcmc顺序:乙醇铵<二乙醇铵<三乙醇铵。粘度大小顺序为:乙醇铵<二乙醇铵<三乙醇铵,有机反离子的粘度要大于无机反离子。这与分子量、氢键大小的关系是一致的。总体来说发泡能力:乙醇铵>二乙醇铵>三乙醇铵,这和γcmc的顺序相符。有机反离子的发泡能力要高于无机反离子。另外,对于同种反离子,全氟辛基磺酸盐的胶束化能力、粘度和发泡能力均明显高于全氟辛酸盐,但是全氟辛基磺酸盐的γcmc要略高于全氟辛酸盐。通过量子化学计算表明分子结构中磺酸根头基的负电荷要小于羧酸根,这样表面活性剂全氟辛基磺酸根的头基与反离子的结合能力要弱于全氟辛酸根,从而导致了溶液表面吸附层中全氟辛酸盐在反离子的协同作用下排列更为紧密。

阴离子蠕虫状胶束的研究进展及油田应用

目前构建蠕虫状胶束主要是使用黏弹性阳离子表面活性剂,而对阴离子蠕虫状胶束的研究和利用还较少。针对这一问题,本文首先介绍了表面活性剂构建蠕虫状胶束的分子几何学特征参数理论;以此为基础,详细阐述了使用无机类反离子和有机类反离子诱导阴离子表面活性剂形成蠕虫状胶束的机理和方法;介绍了黏弹性阴离子蠕虫状胶束溶液在油田开发中的应用;最后指出阴离子表面活性剂构建蠕虫状胶束的发展方向。

原子力显微镜分析聚二甲基二烯丙基铵盐的吸附和絮凝行为:反离子的影响

通过对聚二甲基二烯丙基氯化铵(PDADMAC)改性得到了高分子量的聚二甲基二烯丙基硝酸铵(PDADMANO3)和聚二甲基二烯丙基硫酸铵(PDADMASO4).通过电导率,比浓粘度,原子力显微镜,以及高岭土悬浊液絮凝试验的残余浊度,Zeta电位和絮凝指数,研究了一价阴离子(Cl-,ON3-)和二价阴离子(SO42-)对聚二甲基二烯丙基铵盐(PDADMAX)的溶液性质、吸附的结构与形貌和絮凝性能的影响.结果表明:不同的反离子对PDADMAX的溶液性质、吸附的结构与形貌和絮凝性能有显著影响.PDADMANO3具有更高的絮凝效率和“电中和作用”,而PDADMASO4具有更宽的最佳絮凝范围和更大的絮体粒径,及更强的“吸附架桥作用”.特别对于聚电解质的吸附和絮凝机理的研究,单个高分子的原子力显微镜图象是一种非常有效地分析方法.

芳香反离子与离子表面活性剂胶团的相互作用

用紫外吸收光谱的方法研究了多种芳香反离子与离子表面活性剂胶团之间的相互作用.发现阳离子表面活性剂和阴离子表面活性剂胶团对芳香反离子的吸收光谱有着显著不同的影响,芳香反离子结构的细微变化可导致光谱特性显著不同.这被解释为阳离子表面活性剂胶团与芳香环之间的阳离子-π相互作用.阳离子-π相互作用需要阳离子表面活性剂分子与芳香反离子具有合适的相对位置与距离.通过测定各混合体系的吸附量证明,不同的芳香反离子在胶团表面有不同的排列方式.NMR的实验结果支持了上述解释.

无机盐对正负表面活性剂混合体系性质的影响

用滴体积法测定了四种离子强度下(μ=0.02,0.05,0.1,0.2mol·kg^(-1),支持电解质为NaBr)C_(12)H_(25)SO_4Na/C_6H_(13)(NC_5H_5)Br 混合体系在五种比例(10:1,3:1,1:1,1:3,1:10)时的临界胶团活度cma(25.℃).提出了无机盐对正负表面活性剂混合体系临界胶团活度的影响程度的计算式.

聚电解质材料——(Ⅰ)复合体系溶液中相互作用的研究进展

聚电解质材料兼有高分子长链和小分子电解质电离的双重结构特征。文中在介绍溶液中聚电解质与小分子盐、表面活性剂以及带相反电荷聚电解质相互作用的基础上,讨论溶液中聚电解质复合体系相互作用的主要影响因素,以期为聚电解质的实际应用和理论研究提供参考。