L-精氨酸-顺丁烯二酸超分子复合物晶体组装中的氢键

一些结构简单的羧酸类有机小分子可能存在于生命起源前的地球上.对这些有机小分子与氨基酸分子相互作用得到的超分子复合物单晶体结构的研究,对于我们理解化学进化过程,探讨生物分子的聚合形式和分子间相互作用的实质有重要意义[1,2].     

基于微流控芯片电泳的生物分子间相互作用研究*

用合适的手段表征生物分子的相互作用对于深刻理解生命过程的本质以及进行医药开发都具有重要意义。将微流控芯片和毛细管电泳相结合的微流控芯片电泳技术具有快速、高效、高通量、样品用量少和易于整合等诸多优势。本文对近年来进行生物分子间相互作用结合常数测定以及结合动力学研究的微流控芯片电泳分离模式、分析方法和芯片检测方法分别做了介绍;简单对比了微流控芯片技术和微阵列生物芯片生物分子间相互作用研究技术;最后分析了微流控芯片技术目前的不足,并对其未来的发展进行了展望。     

基于原子力显微镜的单分子力谱在生物研究中的应用

原子力显微镜被广泛应用于生物研究领域,基于原子力显微镜的单分子力谱可以在单分子、单细胞水平上研究生物分子内和分子间的相互作用。 本文介绍了原子力显微镜单分子力谱在生物分子间相互作用、蛋白质去折叠、细胞表面生物分子、细胞力学性质和基于单分子力谱成像等研究中的最新进展。     

3,4,5-三羟基苯甲酸二聚体氢键结构性质

分子间相互作用在生物和材料等科学中发挥着关键作用,研究分子间相互作用的本质意义重大。氢键是分子间相互作用的一种主要形式,在确定分子构象和晶体结构以及生物分子尤其是核酸和蛋白质的结构功能中起着重要作用[1-3]。苯甲酸衍生物广泛存在于生物大分子内,与生物活性离子通过氢键作用等改变生物活性分子的活性功能,研究苯甲酸衍生物分子间氢键相互作用对于了解生物体内的化学现象具有重要意义。研究表明菱角的抗肿瘤作用明显,实验上已经从菱角中成功提取了活性单体化合物:3,4,5-三羟基苯甲酸二聚体[4],理论研究标题化合物的氢键结构与氢…     

基于DNA纳米结构的分子间相互作用研究

研究生物分子间的相互作用是研究生命本质过程中必不可少的环节.近年来,DNA纳米技术在分子间相互作用的研究中发挥了重要作用,取得了一系列进展. DNA纳米结构具有高度的可编程性和可寻址性,可以利用这些性质采取不同的方式将待测体系修饰在DNA纳米结构上,而且可以精确控制分子的排布、种类、数目等,因此可以作为研究分子间相互作用的模板.在此基础上结合单分子技术,如单分子荧光成像(SMF)、原子力显微术等(AFM),可以实现对单个分子的行为观测.本文首先简述了DNA纳米结构作为研究平台的构建,然后对DNA纳米结构在研究分子间相互作用中的应用进行了阐述,包括用作锚定平台、提供具有一定机械性能的支架以及提供纳米级的微环境,最后对DNA纳米技术的发展进行了总结与展望.     

单分子荧光共振能量转移用于生物大分子构象动态变化过程研究进展

生物大分子参与生命活动的各个过程,在单分子水平上实时观测和分析生物大分子自身的结构动态以及生物大分子相互作用的动态过程,对于深入理解生物大分子的作用机制具有重要意义。自提出以来,单分子荧光共振能量转移技术逐渐展现出其在研究生物大分子构象变化和相互作用过程等方面的巨大潜力,一系列新的作用机理陆续被提出。本文对单分子荧光共振能量转移技术在蛋白质与核酸分子构象动态变化、蛋白质-蛋白质相互作用以及蛋白质-核酸相互作用等方面取得的研究进展进行了综述。     

聚合物单分子力谱的研究进展

在单分子水平研究聚合物体系的分子内及分子间相互作用, 对于揭示其结构-性能的关系, 进而实现对相应功能的调控极为重要. 基于原子力显微镜技术(AFM)的单分子力谱, 由于其操作简单且适用面广, 在单分子研究领域得到了广泛的应用. 本文概括了该技术在生物高分子及合成高分子体系的研究进展. 对于生物高分子体系, 主要介绍了核酸(DNA/RNA)、 蛋白质和多糖(淀粉)的单分子力谱研究及利用各自力学指纹谱对其它分子间的相互作用的研究. 对于合成高分子体系, 主要介绍了聚合物的一级结构与单链弹性的关系及溶剂和聚集态结构等对高分子单链力学性质的影响规律.     

双偏振干涉技术(DPI):生物分子相互作用研究的新工具

双偏振干涉(dual polarization interferometry,DPI)技术是近年来发展起来的一种免标记、实时、高灵敏和高分辨率的表面分析技术.它能够精确测量分子相互作用界面层的密度、厚度和质量的绝对值,可实时获取分子相互作用过程的动力学和结构信息.本文简单介绍了DPI的测量原理、仪器组成并对其与相关检测技术的对比进行了简要的概述;着重介绍了近10年来DPI技术在生物分子相互作用研究方面的应用进展,主要包括蛋白质之间以及与其他分子的相互作用,DNA与各种分子之间的相互作用,生物膜与其他分子的相互作用,蛋白质的吸脱附、聚集和结晶过程监测等;并对DPI技术未来的发展进行了展望.随着技术的不断发展,DPI将会在生物分析、纳米材料表征、能源相关表/界面研究等方面得到广泛应用.     

定量单分子检测研究进展

单分子检测是指在单分子水平上通过生物分子的构象变化、动力学、分子之间相互作用以及对单个分子进行操纵等方式进行检测.作为一种新型超灵敏检测手段,单分子检测在生物分子的定量检测领域有广阔的应用前景,尤其单分子荧光检测技术,近年来取得了很大进展,被广泛用于研究多种生物体系.本文对定量单分子检测的最新研究进展进行了系统综述,主要聚焦于定量单分子检测在生物标志物(包括DNA、酶和miRNA等)的超灵敏检测研究中的应用,及其在研究生物分子结构与动态、生物分子间相互作用、生物分子修饰和活细胞检测等方面的应用,本文也对定量单分子检测的发展方向进行了展望.     

锌试剂与壳聚糖的结合反应机理的研究

为从分子水平认识多糖分子与小分子之间相互作用的机理,应用光谱法研究了壳聚糖(CTS)与锌试剂(ZCN)的相互作用机理;测得ZCN-CTS复合物吸收光谱出现新的吸收峰所需的临界ZCN/CTS摩尔比为2.67×103, CTS对ZCN的最大结合数为6.93×103,实验值与理论值相吻合,证明了多糖与生物探针相互作用理论模型的可靠性;探讨了ZCN与CTS相互作用产生变色反应的机理,认为其是在ZCN与CTS大分子间发生静电相互作用的基础上,主要由ZCN与CTS大分子间的疏水相互作用所引起.     

Interaction of oligopeptides with heparin

This heparin affinity chromatography study revealed some very interesting aspects with respect to oligopeptide retention. The first and most surprising effect observed was that oligopeptides with no aromatic groups were not retained on the column while those with aromatic groups were retained. The aromatic interaction was determined to be related to a charge transfer ‐like interaction as electron donating groups on the aromatic moiety increased retention on the column and electron withdrawing groups on the aromatic moiety deceased retention time. Column retention was dependent on oligopeptide size; the tripeptides were not retained while tetrapeptides and the larger hexapeptides were effectively retained if they contained some aromatic functionality. Retention was pH dependent; low pH's of ∼2.5 were most effective while neutral pH was not effective in retaining the oligopeptides on the heparin affinity column. In addition to the aromatic interaction, retention was dependent on the hydrophobicity of the oligopeptides as well as their ability to hydrogen bond as determined by eluent solvent effects on the heparin affinity column. These results have led us design and carry out other experiments to determine more accurately the type and the degree of oligopeptide to heparin interaction.     

Three novel high performance affinity chromatographic media for the separation of antithrombin III from human plasma.

Novel monodisperse, non-porous, cross-linked poly (glycidyl methacrylate) beads (PGMA) were employed as the support for high performance affinity chromatography. Heparin was covalently attached to PGMA beads by three different coupling methods. Heparin-PGMA-I was prepared by directly coupling amino-groups of heparin with PGMA. Heparin-PGMA-II and III were prepared by the coupling of heparin to amino-PGMA, which was obtained by amination of PGMA. Heparin-PGMA-II was prepared by coupling the carboxyl groups of heparin to amino-PGMA by using water-soluble carbodiimide as coupling reagent, and heparin-PGMA-III was prepared by the reductive amination of heparin and amino-PGMA with sodium cyanoborohydride. The heparin contents of heparin-PGMA-I, II and III were 1.6, 10.2 and 1.0 mg/g beads, respectively. Their affinity capacities for antithrombin III were investigated. Their binding activity to antithrombin III was not proportional to the content of heparin immobilized, and heparin-PGMA-I was the most efficient affinity medium for antithrombin III. The resultant affinity media presented minimal non-specific interaction with other proteins and can be used in a wide pH range. All the three heparin-PGMA beads were exploited for the separation of antithrombin III from human plasma. The purity of antithrombin III obtained was higher than 90%, which was confirmed by high performance size exclusion chromatography.     

Amino acid end-group in commercial heparin. II. Reaction kinetics of the amino end groups with 2,4,6-trinitrobenzenesulfonic acid

Three different commercial heparins were trinitophenylated with 2,4,6-trinitrobenzenesulfonic acid (TNBS) under aqueous conditions. The reaction kinetics of amino groups in heparin with TNBS showed that the reactivities of amino groups were significantly different for free amino groups on heparin, compared to reactivities in peptides and amino acid residues attached to heparin molecules. With TNBS, unreactive amino groups were always present during the reaction.     

Further characterization of the binding of heparin to granulocyte colony-stimulating factor: importance of sulfate groups

Heparin mediates fundamental biological mechanisms through interaction with proteins. Previously, we have shown that standard heparin binds to granulocyte colony-stimulating factor (G-CSF) with an affinity of 4.8 x 10(5) M(-1). To further study the structural features in heparin that are responsible for this interaction, we studied the bindings of G-CSF and N-desulfated and 2,3-O-desulfated heparin by CZE. Results showed that the N-desulfated heparin had a similar affinity for G-CSF ((5.4 +/- 0.9) x 10(5) M(-1)), but the 2,3-O-desulfated heparin had a 1000-fold lower affinity ((3.4 +/- 1.2) x 10(2) M(-1)) in comparison to standard heparin. The results showed that 2,3-O-sulfate groups are more important than N-sulfate groups in heparin-G-CSF interaction.     

Time-dependent conformational change of thrombin molecules induced by sulfated polysaccharides

Dextran sulfate (DS) had a greater ability to elute thrombin adsorbed on a small Sepharose 6B column than heparin did, while chondroitin sulfate A had little ability. It is probable that the strength of the interaction of thrombin depends mostly on the charge-density of strongly acidic sulfate groups in the polysaccharides. The change in intrinsic fluorescence intensity of thrombin with time was closely correlated with the rate of inactivation of the enzyme in the presence of sulfated polysaccharides. Both rates were affected by the pH of the solution in the presence of the polyanions. The rates in the presence of DS were highest at pH 6.05 among the three pHs tested, while they were enhanced only at pH 6.05 by heparin, but not by chondroitin sulfate A. Therefore, extensive charge-neutralization of thrombin by the sulfated polysaccharides is able to induce time- and temperature-dependent intramolecular conformational change (irreversible denaturation) of the enzyme molecules.     

Molecular Spectroscopic Study on the Interaction between Heparin and Neutral Red

The interaction between heparin and neutral red was investigated by molecular spectroscopic methods. The change of all spectra suggested that positively charged neutral red had interacted with negatively charged heparin. The study of influence factors indicated that electrostatic force and hydrophobic bond might be involved in the interaction. The total binding number per disaccharide unit and intrinsic binding constant were obtained using Scatchard model.     

荧光增强型共轭聚电解质的合成及对肝素的双通道检测

通过Suzuki偶联反应制备了含有四苯基乙烯和苯并噻二唑2种结构单元的阳离子型共轭聚电解质P1,并通过核磁共振氢谱确定了2种结构单元的比例为0.803:0.197,与投料比基本一致.当在P1的水溶液中加入不良溶剂THF时,在紫外光照下可以观察到其溶液颜色由土黄色(无聚集态)转变为橙黄色(聚集态).利用P1在不同聚集态下的荧光强度和发光颜色变化,可以实现对肝素的双通道检测.当肝素逐渐滴加到P1的水溶液中,P1的荧光发射强度随着肝素浓度的增加而线性增加,且其最大发射峰峰位发生线性红移,正负电荷饱和时强度达到最大且波长不再移动,该性质可作为双通道检测信号来标定肝素的浓度,从而提高肝素浓度检测的准确性.动态激光光散射的测试以及肝素滴定紫外图谱的变化结果表明,肝素与P1作用时聚集诱导发光和荧光共振能量转移两种作用共存,从而导致了荧光强度的增强,且伴随最大发射波长的红移.     

肝素与HIV-1膜表面蛋白gp120相互作用的预测和模拟

用分子模拟软件研究肝素与HIV-1膜表面蛋白gp120的相互作用.将肝素中的单糖、二糖和三糖片段作为探针对gp120蛋白进行搜索,统计分析确定肝素结合区域.用肝素六糖片段和结合区域进行反应分子对接,获得两种结合模式.最终建立的模型能够很好地解释肝素体外抑制HIV-1的现象,同时对其机理进行了推测.     

Photostability of a photochromic naphthopyran dye in different sol-gel prepared ormosil coatings

A photochromic naphthopyran derivative was embedded in sol-gel prepared thin ormosil films. The resulting samples show high transparency and exhibit a strong red colouration upon irradiation with UV light. The photostability of the photochromic molecules is strongly related to the nature of the embedding ormosil matrix. The introduction of organic functional groups into the inner pore surface of the matrix allows tailoring the chemical environment where the dye molecules will be allocated, in terms of the effectiveness of the interaction between the photochromic molecules and the Si-OH groups on the surface of the pores, affecting the stability of the molecules upon prolonged exposition to UV light. The photostability of the molecules was increased in matrices functionalized with larger organic groups, or with larger amount of modifying groups. In this way the photodegradation of the photochromic molecules could be reduced by a factor of 5, as compared with the photodegradation of the molecules in unfunctionalized silica matrix.     

Investigation of the interactions between the hydrophobic cavities of cyclodextrins and pullulanase

The effects of cyclodextrins and derivatives on the activity and structure of pullulanase were investigated in this study. Our results showed that cyclodextrins and derivatives decreased the activity of pullulanase. This decrease was attributed to the interaction between the hydrophobic cavities of cyclodextrins and pullulanase. The hydrophobic cavity was confirmed to encapsulate the groups of pullulanase molecules by the addition of competitive guests. The results obtained from fluorescence spectroscopy analysis showed that β-CD showed more efficient interactions with pullulanase molecules and the side chain groups of cyclodextrin significantly prevented the interaction between the hydrophobic cavities of β-CD and pullulanase molecules. These findings suggest that the geometric dimension of hydrophobic cavities was crucial for matching between cyclodextrins and pullulanase and steric hindrance caused by side chains led to the decrease of the interaction.