Single‐Molecule Force Spectroscopy on Carrageenan by Means of AFM

A marked difference in force‐extension curves is observed for carrageenan before and after adding NaI buffer in single‐molecule force spectroscopy by means of atomic force microscopy (AFM). The salt‐induced helix conformation in carrageenan treated with an 0.1 M NaI solution was unfolded under the external force, and a long plateau about 300 pN high could be observed in the force‐extension curves.     

Sequence and Chiral Selectivity of Drug–DNA Interactions Revealed by Force Spectroscopy

Differential binding force has been used to precisely characterize the mechanical effect of a drug molecule binding to a DNA duplex. The high‐resolution binding forces measured by the force‐induced remnant magnetization spectroscopy (FIRMS) enable the binding behavior of drug molecules with different chirality and DNA of various sequences to be distinguished. The sequence specificity of Hg²⁺ and daunomycin was revealed by force spectroscopy for the first time, and the results are consistent with those obtained by other techniques. Furthermore, the two isomers of d,l ‐tetrahydropalmatine showed selectivity for two different DNA sequences. One particular useful feature of this approach is that the small molecules under study do not require any labels.     

基于原子力显微镜的高分子单分子力学研究

原子力显微镜(AFM)从根本上改变了人们对单个原子和分子的作用和认识方式。单分子力谱是基于原子力显微镜力的测量方法。概速了近年来利用基于原子力显微镜的单分子力谱研究单个高分子分子内及分子闻作用力的进展。     

The Interactions of Spore‐Coat Morphogenetic Proteins Studied by Single‐Molecule Recognition Force Spectroscopy

Bacillus subtilis can form a spore, which is a dormant type of cell, when its external environment becomes unsuitable for vegetative growth. The spore is surrounded by a multilayered proteinaceous shell called a spore coat, which plays a crucial role in dormancy and germination. Of the over 70 proteins that form the spore coat, only a small subset of them affect its morphogenesis; they are referred to as morphogenetic proteins. How these morphogenetic proteins interact, and furthermore, how they build the ordered, functional coat layers is not well understood. Elucidating the self‐assembly mechanism of individual proteins into such a complex structure may contribute to its potential use in nano‐biotechnology applications for preparing highly organized, robust, and resistant proteinaceous layers. Herein, direct, noncovalent, low‐affinity interactions between the spore‐coat morphogenetic proteins SpoIVA, SpoVID, and SafA were studied by using single‐molecule recognition force spectroscopy in vitro for the first time. Based on the real‐time examination of interactions between these three proteins, a series of dynamic kinetic data were obtained. It was also observed that the SafA–SpoVID interaction was stronger than that of SafA–SpoIVA.     

Direct Identification of Protein–Protein Interactions by Single‐Molecule Force Spectroscopy

Single‐molecule force spectroscopy based on atomic force microscopy (AFM‐SMFS) has allowed the measurement of the intermolecular forces involved in protein‐protein interactions at the molecular level. While intramolecular interactions are routinely identified directly by the use of polyprotein fingerprinting, there is a lack of a general method to directly identify single‐molecule intermolecular unbinding events. Here, we have developed an internally controlled strategy to measure protein–protein interactions by AFM‐SMFS that allows the direct identification of dissociation force peaks while ensuring single‐molecule conditions. Single‐molecule identification is assured by polyprotein fingerprinting while the intermolecular interaction is reported by a characteristic increase in contour length released after bond rupture. The latter is due to the exposure to force of a third protein that covalently connects the interacting pair. We demonstrate this strategy with a cohesin–dockerin interaction.     

缓蚀剂吸附行为的电化学及AFM力曲线研究

结合极化曲线,微分电容曲线测试和AFM力曲线技术研究了直链十二胺对氯化钠溶液中铜镍合金的缓蚀行为以及吸附机理。结果表明:十二胺在合金表面形成单分子层吸附膜而起到缓蚀作用。十二胺浓度越大,吸附膜越致密,缓蚀率越高,力曲线上测得的粘附力值也越大。质子化的十二胺在荷负电的合金表面的吸附使电极零电荷电位正移,电荷屏蔽作用使得AFM力曲线上探针与试样之间的长程静电斥力减小。     

有机非线性光学晶体NPP的AFM研究

有机二阶非线性光学活性晶体的分子设计和晶体工程是复杂而又引人注目的课题．有机非线性光学晶体N一忡硝基苯基）－LWe脯氨醇（NPP）是一个极为成功的自］子山．由于在＊＊P分子中引入了含手性碳原子和可形成分子间氢键的电子给体脯氨醇，使得其分子跃迁偶极矩与单科P21晶体结构的二重轴之间的夹角为586”．接近于理论优化值（54．74”），因此，＊＊P具有很高的宏观二阶非线性光学活性，其粉末二次谐波强度为尿素的150倍．自1984年首次报导以来，对它的晶体生长门和物理性质已进行了广泛深入的研究．原子力显微镜（＊＊M）能够以极高…     

光谱法结合原子力显微镜和分子对接技术研究金丝桃苷与人血清白蛋白的相互作用

在模拟生理条件下,采用荧光、共振散射、圆二色谱(CD)等光谱法和原子力显微镜及分子对接技术,研究了金丝桃苷与人血清白蛋白(HSA)的相互作用。应用分子对接技术预测金丝桃苷结合在HSA的SiteⅠ位,预测结果与位点探针竞争实验结果吻合。原子力显微镜(AFM)图像和共振散射光谱表明,与金丝桃苷结合后HSA的分子直径变大,产生相互聚集。金丝桃苷对HSA内源荧光的猝灭机制属于形成基态复合物所引起的静态猝灭。测得的热力学参数表明,金丝桃苷与HSA作用主要由疏水作用和氢键驱动。根据Frster非辐射能量转移理论求得两者间的结合距离为3.52nm。CD谱显示金丝桃苷诱导HSA的二级结构产生稍许的变化。     

All-atom Molecular Dynamics Simulationsand NMR Spectroscopy Study on Interactions and Structures in N-Glycylglycine Aqueous Solution

All-atom molecular dynamics (MD) simulation and the NMR spectra are used to investi-gate the interactions in N-glycylglycine aqueous solution. Different types of atoms exhibit different capability in forming hydrogen bonds by the radial distribution function analysis. Some typical dominant aggregates are found in different types of hydrogen bonds by the statistical hydrogen-bonding network. Moreover, temperature-dependent NMR are used to compare with the results of the MD simulations. The chemical shifts of the three hydrogen atoms all decrease with the temperature increasing which reveals that the hydrogen bonds are dominant in the glycylglycine aqueous solution. And the NMR results show agreement with the MD simulations. All-atom MD simulations and NMR spectra are successful in revealing the structures and interactions in the N-glycylglycine-water mixtures.     

Force measurements on hydrophobized silica surfaces by using AFM

Force measurements between SiO₂ surfaces with and without adsorbed phenyl groups in aqueous media using the atomic force microscope (AFM) are compared. An oxidized silicon tip and an oxidized silicon wafer were hydrophobized with phenyl groups, and the long-range attraction induced by hydrophobation is shown in force vs. distance curves. The observed differences prove that the silanol groups of the unmodified SiO₂ surface are replaced by the phenyl groups. Received: 4 May 1998 / Revised: 1 July 1998 / Accepted: 5 July 1998     

Force measurements on hydrophobized silica surfaces by using AFM

Force measurements between SiO₂ surfaces with and without adsorbed phenyl groups in aqueous media using the atomic force microscope (AFM) are compared. An oxidized silicon tip and an oxidized silicon wafer were hydrophobized with phenyl groups, and the long-range attraction induced by hydrophobation is shown in force vs. distance curves. The observed differences prove that the silanol groups of the unmodified SiO₂ surface are replaced by the phenyl groups. Received: 4 May 1998 / Revised: 1 July 1998 / Accepted: 5 July 1998     

利用原子力显微镜和分子技术研究海水微生物腐蚀(英文)

生物膜在自然界无处不在,但生物膜造成的腐蚀却基本上被忽视.本文展示了几种化学和微生物学新方法在海水微生物腐蚀研究中的应用.原子力显微镜用来揭示生物最初形成的机理和钢在受污染海水中的腐蚀程度,16SrDNA/RNA技术则用来分析生物膜中的微生物组成.试验结果表明,微生物腐蚀在6d内就已经开始了,腐蚀体积与时间的2.83次方成正比;腐蚀生物膜中的微生物以硫酸还原菌(脱硫弧菌科)为最多,其次是梭状芽孢杆菌.     

原子力显微镜对细胞色素C分子结构的形态研究

用原子力显微镜(AFM)对不同浓度下细胞色素C的分子形态,以及加入蛋白质降聚和变性剂脲后的形态变化进行了考察。实验结果显示,在50μmol/L的低浓度溶液中细胞色素C分子主要以直径为3nm的类球形单体形式存在。浓度增大,细胞色素C分子发生聚集,且随着浓度的进一步增大,细胞色素C分子倾向于形成更大的聚集体。浓度为200μmol/L时,聚集体分子间相互缠绕,形成链状结构。浓度低于0.8mol/L的脲的加入基本不影响细胞色素C分子的形态。加入较高浓度的脲,细胞色素C聚集体的聚集数降低,聚集体分子间没有明显的链状结构。     

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.     

Depth Profiling by AFM Nanoindentations and Micro‐FTIR Spectroscopy for the Study of Polymer Ageing

Summary: A method of depth profiling by AFM nanoindentations is developed for the characterisation of the heterogeneity of the mechanical properties of oxidised polymers. An increase or a decrease of the sample stiffness is measured close to the surface. A comparison with micro‐FTIR profiles and a knowledge of the photooxidation mechanism permit an interpretation of the chemical and physical changes and give new insights into the understanding of the ageing behaviour.

Photooxidation profile of a TMPC film measured by AFM (•) and by micro‐FTIR (♦) after irradiation.     

Interactions between Human Serum Albumin and Sulfadimethoxine Determined Using Spectroscopy and Molecular Docking

Sulfonamides are widely used antibiotics in agricultural production. However, the potential threat of these drugs to human health has increased global concern. Human serum albumin (HSA) is the main reservoir and transporter of exogenous small molecules in humans. In this study, the interaction between sulfadimethoxine (SMT) and human serum albumin (HSA) was studied using spectroscopy and computer simulation. Our results showed that the hydrogen bonding and van der Waals forces drove SMT to enter the binding site I of HSA spontaneously and resulted in the fluorescence quenching of HSA. The stability of the HSA–SMT complex decreased with an increase in temperature. The binding of SMT to HSA induced alterations in the secondary structure of HSA, where the content of α-helix decreased from 61.0% of the free state to 59.0% of the compound state. The π–π, π–σ, and π–alkyl interactions between HSA and SMT were found to play important roles in maintaining the stability of the complex.