光谱法在分子间非共价相互作用中的应用及进展

对光谱法在分子间非共价相互作用中的应用作了较详细的评述。重点介绍了紫外、荧光、圆二色、红外、激光拉曼、共振散射等方法在分子间相互作用研究中的应用及进展,总结了这些方法的优缺点。紫外-可见吸收光谱简便、快速,荧光光谱法可获得分子间作用的结合常数、结合位点数及作用方式等信息,圆二色谱法是测定作用前后生物大分子构象变化的有效方法,红外光谱法可提供蛋白质二级结构及构象变化的谱学信息,拉曼光谱法是研究溶液中生物大分子构象变化的有效技术,表面等离子共振(SPR)技术能在保持生物分子天然活性的条件下实时检测分子间的相互作用。     

弹性蛋白力学特性的单分子力谱

弹性蛋白是一类有着特殊力学特性的蛋白.在生物体内它们是承受和传递力的主要媒介;在生物体外,它们更是被广泛地用作高强度的生物材料.根据其功能不同,弹性蛋白的力学特性也各异.有些具有比较高的力学强度,有些则具有较大的延展性和弹性.科学家们很早就采用多种手段来人工合成弹性蛋白用于材料和纳米领域,但对于弹性蛋白的力学特性和序列结构之间的关系还不甚明晰.本综述介绍通过单分子力谱的实验方法来直接表征单根蛋白质在受力下结构的变化,研究其力学特性.基于Bell模型,推导出了蛋白质解折所需力与拉伸速率之间的关系,揭示了蛋白质力学强度的动力学特性,当拉伸速率较低时,解折叠力将正比于拉伸速率,对于较大的拉伸速率,解折叠力与拉伸速率成指数关系;探讨了决定蛋白质力学特性的结构因素和调控蛋白质力学特性的实验方法;介绍了单分子力谱测量的实验方法,包括基于光镊、磁镊和原子力显微镜的单分子力谱技术,着重介绍了原子力显微镜单分子力谱,并特别介绍了多聚蛋白技术来提供单分子测量的"指纹谱"和提高测量效率;论述了基于原子力显微镜单分子力谱研究蛋白质力学特性的最新进展,包括提高原子力显微镜的稳定性和力分辨率的方法,与荧光标记法相结合来提高实验效率的技术和高速扫描原子力显微镜;阐述了如何通过单分子力谱实验来理性设计蛋白质材料的力学特性,并对未来的研究热点做了展望.     

单分子荧光检测在生命科学中的应用

文章对单分子荧光检测在分子马达、离子通道、信号分子、蛋白折叠、蛋白构象变化动力学、酶活性反应、细胞过程实时观察等生命科学领域中的应用进行了介绍.这些研究结果表明,单分子荧光检测在研究生物大分子的活动规律与机制方面不但有着无法替代的优越性,而且有着广阔的发展空间.     

分子吸收光谱在生物大分子研究中的应用

综述了近年来分子吸收光谱法在生物大分子结构研究中的应用,重点介绍了利用分子吸收光谱法研究蛋白质、核酸结构及其与小分子的相互作用。分子吸收光谱法因其简便、快速的特点而广泛应用于生物大分子结构的测定。紫外光谱法常用于从分子水平上研究小分子如抗癌药物与核酸作用的机理,并应用于小分子作为光谱探针测定蛋白质、核酸构象的变化。傅里叶变换红外光谱法主要应用于蛋白质二级结构的测定,运用傅里叶自卷积将重叠的酰胺带进行处理,获取蛋白质二级结构的含量信息,从而使傅里叶变换红外光谱法成为揭示蛋白质构象变化的重要工具。     

半胱胺单分子膜结构的表面增强拉曼散射研究(英文)

在金属电极表面所形成的有机分子的单分子膜或薄膜对于基础研究和实际应用都有着极其重要的意义。以化学吸附形式在金电极表面所形成的半胱胺单分子膜,常常用于蛋白质等生物大分子在金属表面进行吸附的连接层,以避免这些生物大分子在金属表面直接吸附而造成的变性、失活现象的发生。本文报道了我们采用表面增强拉曼散射光谱方法研究在金电极表面吸附的半胱胺单分子膜的结构特征。研究结果表明,在金电极表面所形成的半胱胺单分子膜中,半胱胺分子主要的构型为扭转构型。在与金表面的相互作用中,由于除巯基的结合作用以外,还存在半胱胺分子中端基氨基和金表面较强的亲和性,使得以扭转构型吸附在金表面的半胱胺单分子膜相当稳定。这是金电极表面的半胱胺单分子膜结构的主要行征。当考察外加电势对此单分子膜结构的影响时,可以发现有关扭转构型的特征谱峰其相对强度随着电位负移而减小。这一结构随电位的变化关系可以通过表面电势的变化对氨基氮原子上孤对电子与金属表面间相互作用的影响来加以阐释。     

单分子的荧光特性及其在生物学上的应用

近年来,单分子探测在许多学科领域的研究取得了显著的进展。它为科学家提供了一种新的手段来研究这些领域的前沿课题。光学和光谱技术是单分子探测最常用的方法之一。单个分子的荧光强度的涨落及其荧光的偏振特性是单分子荧光的重要特征,在单分子探测的广泛应用中,人们正是利用这种单个分子的重要特征来研究和推测生物大分子的结构和功能。文章简要介绍了单分子的荧光特点、探测方法及其在生物学中的应用。     

生物分子结合水的结构与动力学研究进展

生物结合水在维护生物大分子的结构、稳定性以及调控动力学性质和生理功能等方面起着决定性的作用.从分子水平上理解生物结合水分子的结构与性质及其影响生物结构和功能的本质与规律,是揭示生物大分子生理功能机理的关键.目前生物结合水的结构与动力学相关研究尚处于初步阶段.本文从三个方面介绍当前生物结合水的相关研究及其进展:首先介绍结合水对蛋白质折叠、质子给予与迁移、配体结合与药物设计以及变构效应等生物结构和功能的影响;然后介绍生物分子周围的水分子结构研究情况;最后从时间尺度、动力学属性、生物分子与水分子之间的动力学耦合作用、蛋白质表面结合水次扩散运动等角度介绍生物分子水合动力学的研究进展,并归纳出一些目前尚待进一步解决的科学问题.     

表面单分子量子态的探测和调控研究进展

单分子体系是一种典型的受限量子体系,且由于其能级分立、轨道局域、化学拓展性强,因而具有丰富的电子态、光子态以及自旋态,这些分子体系中由量子力学决定的物态使得利用单分子作为未来量子信息的载体成为可能.对单分子尺度量子态的探测和调控研究有利于我们“自下而上”精确构建量子器件.由于单分子体系的尺寸限制,宏观的表征手段难以对其进行精确地调控和探测.扫描隧道显微镜具有高精度的实空间定位能力,高分辨的成像和谱学能力,可以实施原位的分子操纵,还可以与多种外场和局域场表征技术联用,是目前精确探测和调控分子尺度量子态特性的重要工具.本文撷取这一领域较为代表性的进展,介绍了基于扫描隧道显微学技术的表面吸附单分子及其相关结构中的量子态研究现状.首先介绍了表面单分子体系量子态的制备手段,然后分别重点介绍了单分子的局域磁自旋态以及单分子作为单光子源的光学特性.对于石墨烯分子结构我们将其视为一种大分子的单分子体系,分别从其拓扑电子态和自旋态的表征和调控两方面做了介绍.最后总结并对单分子量子态研究未来的发展做了展望.     

生物物理讲座 第六讲 生物大分子中的相互作用

核酸、蛋白质等生物大分子是构成生命的主要物质基础.研究它们的结构与功能是现阶段认识生命现象的中心环节.生物大分子的一个重要特点,就是其三维结构对其功能有极大的影响.所谓三维结构,是指分子在三度空间中的立体结构,亦即组成分子的所有原子的特征空间排布.三维结构也常称为空间结构.现在,越来越多的研究结果使人们认识到,没有特征的三维结构就没有复杂的核酸和蛋白质的功能.蛋白质是生命现象的功能分子.为了适应各种各样的生物功能,不同的蛋白质需要有不同的立体结构.在一定意义上,可以说是一个蛋白质分子对应一种立体结构.核酸是信息…     

旋转分子马达的代表——ATP合成酶

 所有生物的运动系统都与能量的输运有着密切的联系。这主要是由于具有马达功能的大分子蛋白质做功的结果,这些蛋白质分子被称为分子马达或蛋白质马达。它们在体内占有特殊的地位,是生命活动和生命现象的主要承担者。这些运动系统有一个共同的特点即ATP(三磷酸腺苷)水解释放的能量通过分子马达的构象变化可高效地将化学能转换为机械能。因此,分子马达就起到了能量转换器的作用。分子马达的运动协调起来就产生了宏观的运动。但是,这些运动如何协调起来产生生命现象和生命活动,则需进一步研究。到目前为止,人类已确定了上百种马达,它们在机体内执行着各种各样的功能,已经知道的分子马达有线性分子马达和旋转分子马达。     

Mechanism and Properties of Non-Thermally Biological Effect of the Millimeter Waves

The electromagnetic features of biomacromolecules are foundation of interaction between the millimeter waves and living systems. Therefore we first reveal the electromagnetic features of biomacromolecules, for example, protein, DNA and lipid. Next we calculate the rotational energy-spectra of these biomacromolecules by quantum mechanical theory. The transitions of electrons between the rotational energy-levels can result in radiations or absorptions of millimeter waves. Thus we propose the mechanism and properties of non-thermally biological effect of the millimeter waves, i.e., the millimeter waves are absorbed by these biomacromolecules which can result in rotation and changes of conformations of these molecules, thus the energy of the millimeter waves are to be transformed as the mechanical energy of the conformation changes of the biomacromolecules, but not as thermal energy of motions of these biomacromolecules to increase their temperature. This mechanism is verified by experiments of conformation changes of the protein and amino acid molecules exposed under the millimeter waves. These rotations of conformations of these molecules can results in obvious biological effects. We study the features of the biological effects.PACS numbers: 33.20.-Eat, 33.10.-n, 78.30.-j; 87.50. Hi     

Quantitative imaging of electrospun fibers by PeakForce Quantitative NanoMechanics atomic force microscopy using etched scanning probes

Electrospun polymeric submicron and nanofibers can be used as tissue engineering scaffolds in regenerative medicine. In physiological conditions fibers are subjected to stresses and strains from the surrounding biological environment. Such stresses can cause permanent deformation or even failure to their structure. Therefore, there is a growing necessity to characterize their mechanical properties, especially at the nanoscale.Atomic force microscopy is a powerful tool for the visualization and probing of selected mechanical properties of materials in biomedical sciences. Image resolution of atomic force microscopy techniques depends on the equipment quality and shape of the scanning probe. The probe radius and aspect ratio has huge impact on the quality of measurement.In the presented work the nanomechanical properties of four different polymer based electrospun fibers were tested using PeakForce Quantitative NanoMechanics atomic force microscopy, with standard and modified scanning probes. Standard, commercially available probes have been modified by etching using focused ion beam (FIB). Results have shown that modified probes can be used for mechanical properties mapping of biomaterial in the nanoscale, and generate nanomechanical information where conventional tips fail.     

Atomic force microscopy probing of cell elasticity

Atomic force microscopy (AFM) has recently provided the great progress in the study of micro- and nanostructures including living cells and cell organelles. Modern AFM techniques allow solving a number of problems of cell biomechanics due to simultaneous evaluation of the local mechanical properties and the topography of the living cells at a high spatial resolution and force sensitivity. Particularly, force spectroscopy is used for mapping mechanical properties of a single cell that provides information on cellular structures including cytoskeleton structure.

This entry is aimed to review the recent AFM applications for the study of dynamics and mechanical properties of intact cells associated with different cell events such as locomotion, differentiation and aging, physiological activation and electromotility, as well as cell pathology. Local mechanical characteristics of different cell types including muscle cells, endothelial and epithelial cells, neurons and glial cells, fibroblasts and osteoblasts, blood cells and sensory cells are analyzed in this paper.     

A new approach to the evaluation of Casimir and van der Waals forces in the transition region

This paper studies the incorporation of Casimir and van der Waals forces applied to a nanostructure with parallel configuration. The focus of this study is in a transition region in which Casimir force gradually transforms into van der Waals force. It is proposed that in the transition region, a proportion of both Casimir and van der Waals forces, as the interacting nanoscale forces, can be considered based on the separation distance between upper structure and substrate during deflection. Moreover, as the separation distance descends during deflection, the nanoscale forces could transform from Casimir to a proportion of both Casimir and van der Waals forces and so as to van der Waals. This is also extended to the entire surface of the nanostructure in such a way that any point of the structure may be subjected to Casimir, van der Waals or a proportion of both of them about its separation distance from the substrate. Therefore, a mathematical model is presented which calculate the incorporation of Casimir and van der Waals forces considering transition region and their own domination area. The mechanical behavior of a circular nano-plate has been investigated as a case study to illustrate how different approaches to nanoscale forces lead to different results. For this purpose, the pull-in phenomena and frequency response in terms of magnitude have been studied based on Eringen nonlocal elasticity theory. The results are presented using different values of the nonlocal parameter and indicated in comparison with those of the classical theory. These results also amplify the idea of studying the mechanical behavior of nanostructures using the nonlocal elasticity theory.     

微平面接触分离中弯月面力的计算

微平面间黏着力对微机电系统(MEMS)非常重要,常是决定其能量损耗乃至寿命长短的最主要因素.MEMS中的黏着力主要来源之一就是介于两互相接触平面间的弯月面力.弯月面力主要取决于相互接触的两平面间形成的弯月面形状.本文通过分析两微小平面在分离过程中弯月面形状的变化,得到在不同表面亲水/疏水性能、初始液面高度、分离距离等条件下的弯月面形状,计算得出在不同初始条件下断裂高度和弯月面力的数值以及随之变化的规律,为MEMS的性能分析和寿命计算提供依据。     

钙离子调控微丝切割蛋白中A6亚基解折叠的单分子力谱研究

在生命活动中,金属离子扮演了非常重要的角色.微丝切割蛋白(adseverin)需要钙离子的活化才能行使其切割肌动蛋白微丝的功能.本文通过基于原子力显微镜的单分子力谱研究了微丝切割蛋白C端末的A6亚基在结合钙离子前后的力学解折叠机理.实验结果显示:在未结合钙离子时,A6的解折叠表现为两态过程;在结合钙离子后A6力学稳定性显著提高;同时,钙离子的结合使得A6解折叠过程中出现稳定的中间态.通过对中间态的链长的分析,我们推测了中间态对应着A6的N端部分解折叠.而这一部分的解折叠可以使得掩藏在该结构后的A5亚基中肌动蛋白微丝结合位点暴露,从而促使微丝切割蛋白执行功能.我们的实验结果为理解微丝切割蛋白的工作原理提供了新的实验证据.     

The structure of neutron-rich calcium isotopes studied by the shell model with realistic effective interactions

We study the structure of neutron-rich calcium isotopes in the shell model with realistic interactions. The CD-Bonn and Kuo-Brown (KB) interactions are used. As these interactions do not include the three-body force, their direct use leads to poor results. We tested whether the adjustment of the single particle energies (SPEs) would be sufficient to include the three-body correlations empirically. It turns out that the CD-Bonn interaction, after the adjustment of SPEs, gives good agreement with the experimental data for the energies and spectroscopy. For the KB interaction, both the SPEs and monopole terms require adjustments. Thus, the monopole problem is less serious for modern realistic interactions which include perturbations up to the third order. We also tested the effect of the non-central force on the shell structure. It is found that the effect of the tensor force in the CD-Bonn interaction is weaker than in the KB interaction.     

Morse势函数和钼单晶等的临界切应力的温度依赖性

综述了以往钼、铁、铝、镁等单晶临界切应力温度依赖性的实验；指出：在滑移系统不变的条件下，在一定的温度范围内，临界切应力和温度呈近似指数关系是相当普遍的规律。Ｍｏｒｓｅ势函数应用和实验的吻合说明原子间力对屈服应力的重要作用。结合近来发展讨论今后的发展，指出金属范性的本质深入到电子结构层次研究的重要意义。     

Study of the vibrational spectra of (CH3)3GeCl from experimental and DFT calculations

New infrared (for gas and liquid phase) and Raman (for liquid) spectra were measured for the chlorotrimethylgermane to obtain a complete assignment of its fundamental modes. The measurement of the low‐temperature infrared spectrum together with the application of Fourier self‐deconvolution to the Raman spectra resolves the C H vibrational modes into their components. The Rauhut and Pulay scaled quantum mechanical (SQM) force field methodology and the wavenumber‐linear scaling (WLS) method were used to predict the vibrational spectra as a guide to the assignment of the fundamental bands. A quantum mechanical analysis was carried out to obtain the harmonic force field. Copyright © 2009 John Wiley & Sons, Ltd.     

原子力显微镜在生物物理领域的新应用

介绍了原子力显微镜在生物物理领域的最新应用:蛋白质去折叠、DNA拉伸、生物膜受力,通过分析实验得到的力谱,可以获取关于蛋白质、DNA、生物膜结构信息.原子力显微镜不仅能反映测量体系的力学性质,由于其具有独特的时间、空间分辨及实时成像,因而能提供更多信息.