Sequestration of Methylene Blue into Polyelectrolyte Complex Coacervates

Polyelectrolyte complex coacervation is a process that has been proposed as a model for protocell formation due to its ability to compartmentalize chemicals in solution without a membrane. During the liquid–liquid phase separation that results in water rich and polyelectrolyte rich phases, small molecules present in solution selectively partition to one phase over the other. This sequestration is based on relative affinities. Here, a study of the sequestration of methylene blue (MB) into the complex coacervate phase of three pairs of synthetic polyelectrolytes is presented; branched polyethylene imine with polyacrylic acid, polyvinyl sulfonate, or poly(4‐styrenesulfonic acid). These materials are characterized with UV–vis, zeta potential measurements, and dynamic light scattering. The branched polyethylene imine/poly(4‐styrenesulfonic acid) system is shown to have a significantly higher sequestration capacity for the MB as compared to either of the other two systems, based on π–π interactions which are not possible in the other systems.

     

Competition between Liquid-liquid De-mixing,Crystallization, and Glass Transition in Solutions of PLA of Different Stereochemistry and DEET

Liquid-liquid(L-L)de-mixing and vitrification of solutions of either crystallizable poly(L-lactic acid)(PLLA)or non-crystallizable poly(D/L-lactic acid)(PDLLA)with 50 m%N,N-diethyl-3-methylbenzamide(DEET)were analyzed by calorimetry and cloud-point measurements,which allows drawing conclusions about the effect of polymer stereochemistry on the phase behavior.Regardless of the PLA stereochemistry,vitrification of the solutions on fast cooling,hindering crystallization of PLLA,occurred below-20℃ and suppressed prior L-L de-mixing.The experimental results prove that crystallization in samples containing crystallizable PLLA,observed at around 55℃ on slow cooling,is not preceded by L-L de-mixing.     

聚羟基丁酸酯共聚物超薄膜中向日葵晶形成的原子力显微镜观察

低维数下的高分子(如在二维薄膜或一维管道及孔洞中)的各种行为由于更加触及高分子的动力学、热力学本质而逐渐成为高分子科学研究的热点之一．实验表明,薄膜中聚合物的玻璃化转变温度、结晶动力学及形貌等与本体有很大的偏离．我们先前的研究结果表明,在基板的作用下,共混物薄膜的相形态会发生逆转;     

Self-assembly of Amphiphilic Diblock Copolymers Induced by Liquid-Liquid Phase Separation

The liquid-liquid phase separation(LLPS) widely exists in biology, synthetic chemistry, crystallization kinetics and other fields, and it is very important to realize the related functions. The research on the competition between LLPS and micellization/vesiculation has made considerable progress. However, the way to effectively control the formation paths from homogeneous state to aggregates has not been completely solved, which is vital to determine its structure and properties and even its fut...     

热致相分离法偏二氯乙烯-氯乙烯共聚物多孔膜的制备及性能

以偏二氯乙烯-氯乙烯共聚物[P(VDC-co-VC)]为成膜聚合物, 邻苯二甲酸二甲酯(DMP)为稀释剂, 采用热致相分离(TIPS)法制备了具有多孔结构的P(VDC-co-VC)膜. 通过聚合物-稀释剂二元体系相图、 场发射扫描电镜(FESEM)、 差示扫描量热仪(DSC)、 X射线衍射(XRD)、 原子力显微镜(AFM)、 纯水通量、 接触角、 孔径及其分布、 截留率及力学性能等研究了聚合物含量对P(VDC-co-VC)多孔膜结构和性能的影响. 结果表明, P(VDC-co-VC)-DMP二元体系成膜过程以液-液(L-L)分相为主, 随着聚合物含量增加, 膜的横截面由类花瓣状结构向胞腔状结构转变, 膜的孔连通性降低, 结构变得较为致密, 同时膜上表面孔隙率降低, 粗糙度增大. L-L分相时间和聚合物含量的变化, 导致膜结晶度先降低后增大. 聚合物含量的增加使膜上表面接触角、 断裂强度及蛋白截留率增加, 但膜的平均孔径、 孔隙率及纯水通量先增加后减小. 当聚合物质量分数为30%时, 所得膜通透性较优, 断裂强度可达7.5 MPa.     

Spatiotemporal organization of coacervate microdroplets

Liquid–liquid phase separation (LLPS) has emerged as a new paradigm in the fields of soft matter, colloid chemistry, prebiotic chemistry, and cell biology. As phase separation is a dynamic assembly process, how to spatiotemporally regulate the assembly and disassembly of these micrometre-sized droplets, which are referred as biomolecular condensates in biology is essential for their diverse applications in various disciplines. Herein, we discuss recent advances in the spatiotemporal control of phase separation using different physical tools and external environmental stimuli in bulk solutions and living cells. Specifically, the exploration of phase transition in a compartmentalized protocellular system, which can bridge the gap between synthetic and intracellular LLPS systems, is summarized, and the challenges and future research directions are discussed.     

晶状体蛋白识别互作与白内障的研究进展

白内障是全球致盲率最高的眼科疾病, 发病组织为晶状体. 晶状体内纤维细胞含有高浓度的晶状体蛋白, 晶状体蛋白家族分α?, β?和γ?3大亚家族. α-晶状体蛋白具有小分子伴侣功能, 可识别错误折叠蛋白质, 维持晶状体内蛋白质稳态; β?/γ?晶状体蛋白通过分子内或分子间相互作用, 主要发挥结构蛋白功能. 晶状体蛋白在晶状体纤维细胞内呈瞬时有序排列, 精准分子识别及动态相互作用在维持晶状体透明度中发挥关键作用. 晶状体内蛋白质稳态失衡是白内障的主要致病因素. 晶状体蛋白半衰期长, 且翻译合成后不再更新, 广泛受pH值、 金属离子、 辐射损伤和蛋白质翻译后修饰等细胞内外环境因素和化学因素的干扰, 影响晶状体蛋白间的分子识别和相互作用, 诱发白内障. 理清化学调控的晶状体蛋白分子识别及互作调控, 有助于阐明白内障发病机理, 并发掘防治白内障的创新策略. 本文基于晶状体蛋白识别互作与白内障研究进展, 综合评述了晶状体蛋白的分子识别、 相互作用方式、 调控因素及研究技术创新, 并探讨了晶状体蛋白识别互作调控网络在白内障药物研发的应用价值与挑战.     

Mechanical properties of hard–soft block copolymers calculated from coarse-grained molecular dynamics models

To relate the mechanical responses of hard–soft copolymer systems with their microstructures, a coarse-grained molecular dynamics approach is employed, and mechanical properties of both hard and soft domains are calculated. We first investigate the enhancement mechanism of hard domains under tensile and shear loading conditions with pressure. The energy factor that denotes the interaction between hard beads dominates the microphase separation and morphology. Our numerical experiments show that pressure is the most crucial factor in shear-under-pressure tests, with larger pressure leading to higher shearing resistance of the copolymers. The viscoelastic behaviors of hard–soft copolymers are computed from the stress autocorrelation function. The stress relaxation indicates that the soft matrix is in a rubbery state at room temperature while hard domains are “glass-like” and can be viewed as elastic solids in a macroscale model. In addition, local elastic constants of hard domains are computed using the stress–strain fluctuation method with purely local stress and local strain. Those results can be used as inputs for macroscale models for copolymers and can provide guidelines for designing polymeric materials. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1552–1566     

凝聚体及其在人造细胞领域中的应用

生命起源问题一直受到科研工作者的广泛关注,合成生物学家致力于构建较为简单且在原始地球条件下合理的隔室体系来模拟原始细胞.凝聚体是聚合物间静电相互作用所产生的的相分离体系,是一种可能的原始细胞结构,广泛应用于人造细胞的构建.同时,目前很多研究发现这种凝聚体在细胞内构成多种亚细胞器结构,因此对于凝聚体作为人造细胞器的研究也开始兴起.作者详细综述了凝聚体的形成机理、特性和分类,并且针对凝聚体作为人造细胞器和人造细胞的研究进行了总结,归纳概括了该领域发展仍需解决的科学问题,并对该领域的发展进行了展望.     

Polymer chain conformation in the phase separation process of a binary liquid mixture

A polymer chain conformation change near the critical point of liquid-liquid phase separation was investigated. Poly(N-isopropylacrylamide) labeled with a small amount of carbazolyl group for a fluorophore (P(NIPA-Cz)) was prepared. A ternary system of P(NIPA-Cz)+cyclohexane+methanol was investigated by the fluorescence spectroscopic technique. A mixed solvent of cyclohexane+methanol (CH/MeOH) shows phase separation at the upper critical solution temperature. Light scattering intensity, fluorescence emission intensity and fluorescence anisotropy ratio, as a function of temperature, were measured with quasi statically approaching to the critical demixing point. The fluorescence intensity of the carbazolyl groups attached to the polymer chain decreases with approaching to the critical temperature. This result suggests that the radius of gyration of the polymer decreases upon approaching to the critical demixing point of the solvent. We discuss the collapse and aggregation processes of the polymer based on the fluorescence quenching method. The rotational diffusion coefficient of carbazolyl groups attached to the polymer chain was estimated by the fluorescence depolarization technique. The rotational motion of carbazolyl groups is slowed down upon approaching the critical point.     

Rapid determination of 95 pesticides in soybean oil using liquid-liquid extraction followed by centrifugation, freezing and dispersive solid phase extraction as cleanup steps and gas chromatography with mass spectrometric detection

A multi-residue method using liquid-liquid extraction (LLE) followed by centrifugation, freezing and dispersive solid phase extraction (dispersive SPE) as clean up steps and gas chromatography with mass spectrometric detection has been developed for the determination of trace levels of 95 pesticides in soybean oil. LLE has been optimized to extract these pesticide residues from soybean oil by studying the effect of different partitions between (i) acetonitrile (MeCN) saturated with petroleum ether and a soybean oil solution dissolved in petroleum ether saturated with MeCN, (ii) partition between MeCN and a soybean oil solution dissolved in petroleum ether saturated with MeCN, (iii) partition between MeCN and a soybean oil solution dissolved in petroleum ether, (iv) partition between MeCN saturated with n-hexane and a soybean oil solution dissolved in n-hexane saturated with MeCN, (v) partition between MeCN and a soybean oil solution, (vi) partition between MeCN and a soybean oil solution dissolved in n-hexane and (vii) partition between MeCN and a soybean oil solution dissolved in mixture of acetone and n-hexane (3:2) to the highest recovery yield of pesticides and the lowest co-extract fat residue in the final extract. Experiments were carried out in order to study the efficiency of using centrifugation and freezing steps as well as the used of primary secondary amine (PSA), florisil, graphite carbon black (GCB) and C18 for dispersive SPE on clean up stages to minimize the co-extract fat. The recoveries obtained ranged from 80 to 114% and the relative standard deviation (RSDs) from 2 to 14% for spiking levels of 0.040, 0.080 and 0.160 mg kg^− 1. The limits of quantification (LOQs) of almost all compounds were below the maximum residue limits (MRLs) established by the Korean legislations for soybean oil.     

环糊精衍生物气相色谱手性固定相研究进展

评述近年环糊精衍生物气相色谱手性固定相的研究进展,对环糊精衍生物进行分类并总结了近年来其在GC手性分离上的应用,介绍环糊精衍生物的手性分离机制及纯度问题进展,展望环糊精衍生物作GC手性固定相的应用前景。     

Selectivity of amylose tris(3,5-dimethylphenyl-carbamate) chiral stationary phase as a function of its structure altered by changing concentration of ethanol or 2-propanol mobile-phase modifier

In a previous publication, solid-state NMR data showed that the structure of Chiralpak AD chiral stationary phase (CSP) was altered by changing the concentration of ethanol or 2-propanol modifier in the chromatographic mobile phase. This present paper reports the effect of the CSP structural change on chiral selectivity alpha. The enantiomers of a series of compounds were chromatographed using ethanol or 2-propanol in various concentrations as mobile-phase modifier and the alpha values were determined. Changes of alpha were observed for some enantiomeric pairs when ethanol and 2-propanol concentrations were varied. These data correlate with previous findings on the structural changes of the CSP. Not every enantiomeric pair showed changes in alpha as the alcohol concentration was varied, indicating that the chiral selectivity depends not only on the CSP's structure, but also on the structures of the analytes.     

Microfluidic Design of Complex Emulsions

Controllable generation of complex emulsions comprising exceptional features such as several compartments and shape anisotropy is becoming increasingly important. Complex emulsions are attracting great interest due to their significant potential in many applications, including foods, pharmaceuticals, cosmetics, materials, and chemical separations. Microfluidics is emerging as a promising route to the generation of complex emulsions, providing precise control over emulsion shape, size, and compartments. The aim of this Minireview is to mainly describe the progress of microfluidic approaches to design complex emulsions using hydrodynamic control and phase separation. The emulsions formed are classified according to their morphology, anisotropy, and internal structure. Emerging applications of complex emulsions formed using these microfluidic techniques are discussed.     

An Update on the Use of Molecularly Imprinted Polymers in Beta-Blocker Drug Analysis as a Selective Separation Method in Biological and Environmental Analysis

Beta-blockers are antihypertensive drugs and can be abused by athletes in some sport competitions; it is therefore necessary to monitor beta-blocker levels in biological samples. In addition, beta-blocker levels in environmental samples need to be monitored to determine whether there are contaminants from the activities of the pharmaceutical industry. Several extraction methods have been developed to separate beta-blocker drugs in a sample, one of which is molecularly imprinted polymer solid-phase extraction (MIP-SPE). MIPs have some advantages, including good selectivity, high affinity, ease of synthesis, and low cost. This review provides an overview of the polymerization methods for synthesizing MIPs of beta-blocker groups. The methods that are still widely used to synthesize MIPs for beta-blockers are the bulk polymerization method and the precipitation polymerization method. MIPs for beta-blockers still need further development, especially since many types of beta-blockers have not been used as templates in the MIP synthesis process and modification of the MIP sorbent is required, to obtain high throughput analysis.     

Direct observation of morphological differences as a function of reaction temperature in model systems for polyurethane foams

A series of polyurea urethanes was isothermally synthesized from toluene diisocyanate (TDI), water, and trifunctional poly(propylene oxide) in the temperature range of 50–150°C. Morphologies of the samples vary significantly as a function of reaction temperature. In this system, phase separation competes with polymerization and crosslinking. Both transmission electron microscopy and atomic force microscopy have shown a network type of structure for the 50°C samples, while the 150°C samples appear to be homogeneous. Infrared analysis shows that samples prepared at 150°C possess a morphology that is less strongly hydrogen bonded and has a broader distribution of hydrogen-bonded states compared to those prepared at lower temperatures. From this combination of techniques, it can be inferred that phase separation occurs faster than crosslinking at low temperatures; consequently, a phase-separated morphology forms. In contrast, crosslinking occurs faster than phase separation at higher reaction temperatures. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3065–3077, 1998     

酰胺型手性固定相直接拆分克仑特罗对映体

 将酰胺型手性固定相用于正相高效液相直接拆分 β2 受体兴奋剂克仑特罗。讨论了三元流动相中正己烷、1,2 二氯乙烷和甲醇含量的变化以及柱温和流速对分离的影响 ;优化了实验条件 :流动相为V(正己烷 )∶V(二氯乙烷 )∶V(甲醇 ) =5 4∶38∶8,柱温为 17℃ ,流速为 1 0mL/min ;并对拆分的机理加以探讨。方法简单、快速。     

涂敷三苯甲酰基纤维素酯手性固定相的制备和表征

以微晶纤维素为原料制备三苯甲酰基纤维素酯（ＣＴＢ）,通过电子透射显微分析考察涂敷ＣＴＢ手性固定相的表面分布和表面浓度,用ＣＴＢ涂敷大孔硅胶高效液相色谱法分离三对旋光异构体,（±）－α－苯乙醇对映体获得完全分离,降冰片烯乙酯和４－十六碳烷氧基－（１′－溴）正壬基苯对映体未完全分开。     

合成高分子作为手性固定相在高效液相色谱中的应用

具有旋光活性的合成高分子基于它的手性结构而具有广泛的应用,其中最实际和广泛的应用是在高效液相色谱中作为手性固定相来拆分对映异构体,目前已成为合成化学、分析化学以及制药化学领域必不可少的分离材料.本文简要介绍了高效液相色谱手性固定相拆分法,综述了合成高分子,包括加聚物特别是聚甲基丙烯酸酯类和聚甲基丙烯酰胺类聚合物、聚酰胺...     

手性共价有机骨架材料CTpPa-1用于HPLC固定相拆分手性化合物

以合成的1,3,5-三甲酰基间苯三酚(Tp)与(+)-二乙酰基-L-酒石酸酐反应形成的手性有机单体CTp作为手性源,与对苯二胺(Pa-1)反应合成了一种二维重叠层状结构的手性共价有机骨架材料(COFs)CTpPa-1,并采用X射线粉末衍射、红外光谱、扫描电镜和氮气吸附等手段对该材料进行表征。将CTpPa-1与C₁₈硅胶混合用作固定相制成了高效液相色谱(HPLC)手性柱,在不同比例的正己烷-异丙醇为流动相的色谱条件下,考察了手性柱对不同类型手性化合物的拆分能力。结果显示,该手性柱对醇类、酮类、酚类、有机酸类、胺类等18种外消旋化合物表现出较好的拆分能力,有5个手性化合物达到基线分离,7种手性化合物接近基线分离,其中最大分离度达3.65。该手性柱对一些位置异构体(硝基苯酚、溴苯胺、二硝基苯)也具有一定的分离能力。此外,1-(4-氯苯基)乙醇在手性柱上进样50、100、150、200、250次后,其保留时间与峰面积的相对标准偏差(RSD)分别为0.86%和1.1%,表明该手性柱具有较好的重现性和稳定性。