正常人脐静脉内皮细胞的原子力显微镜观察

目的:利用原子力显微镜(AFM)在单细胞水平分析正常人脐静脉内皮细胞的形貌特征和机械性质,为了解内皮细胞结构与功能的关系奠定基础.方法:新鲜人脐静脉内灌注质量分数为0.25%胰蛋白酶消化,获得人脐静脉内皮细胞(HUVECs),M199培养基进行培养,免疫细胞化学检测内皮细胞第Ⅷ因子的表达.将体外培养的HUVECs用质量...     

An atomic force microscopy study of coal nanopore structure

Coal nanopore structure is an important factor in understanding the storage and migration of absorbed gas in coal. A new method for studying coal nanopore structures is proposed. This idea is based on the nano-level resolution of atomic force microscopy, which can be employed to observe the structural features of coal nanopores clearly, conduct quantitative three-dimensional measurements and obtain structural parameters. Analysis results show that coal nanopores are mainly metamorphic pores and intermolecul...     

Determination of hydration film thickness using atomic force microscopy

Surface forces between particles control phenomenasuch as dispersion, agglomeration, coatings, adhesion,wetting, friction, and polishing, which play a crucial rolein materials processing. The importance of surface forcesis more appreciated especially in colloidal processing,while materials in a colloidal state are frequently preferredin industrial processing operations (e.g., printing inks,toners, paints, skin creams, blood substitutes, gels used asdrug-delivery systems, etc.) because their lar…     

聚丙烯酸纳米微凝胶的表征

利用原子力显微镜（AFM）对聚丙烯酸纳米微凝胶的形态、结构进行了表征,单体浓度、交 联剂与单体摩尔比对聚丙烯酸微凝胶的粒径都有一定影响,在实验条件下均可得到粒径为20 ～60nm的微凝胶。加入夺氢型光引发剂BP-4进行二次聚合,可以得到大分子纳米凝胶引发剂,其粒径比一次聚合所得微凝胶增大10～20nm;二次聚合时加入N-异丙基丙烯酰胺（NIPAM）可得到50～90nm、表面包覆PNIPAM的纳米凝胶。     

Nanomechanics of individual amyloid fibrils using atomic force microscopy

Compression elasticity of glucagon amyloid fibrils in the transverse direction was investigated by a nanoindentation approach based on atomic force microscopy (AFM).With force-volume mapping, we obtained the correlations between radially applied force and compression of amyloid fibrils, from which the radial compressive elasticity can be deduced.The estimated elastic modulus at three typical locations of fibrils varied from (0.72±0.80) GPa to (1.26±0.62) GPa under small external forces, imply-ing the struct...     

Elimination of bistability in constant-phase mode in atomic force microscopy

By presenting the phase properties of bistability in amplitude-modulation atomic force microscopy, we put forward a technique, the constant-phase mode, which may eliminate bistability. Using this approach, we keep the phase shift between driving and oscillation constant, slightly above -90°. In addition to the adjustment of the free amplitude, we add to amplitude-modulation atomic force microscopy another feedback so that the tip always oscillates in the high-amplitude state. A numerical simulation is carried out to demonstrate that the algorithm prevents bistability effectively.     

杜仲抗真菌蛋白(EAFP)晶体动态生长研究

杜仲抗真菌蛋白(eucommia antifungal protcin,EAFP),含有41个氨基酸残基,其中有10个半胱氨酸,半胱氨酸间形成的二硫桥键使分子构象很稳定.EAFP的晶体属单斜晶系,空间群为P2 1.晶胞参数为:a=1.908 5 nm,b=2.322 5 nm,c=3.085 4 nm10-6,β=98.64,分子量为4158.9.EAFP晶体生长速度快,对X射线的衍射能力强,很值得研究其生长的机理.利用原子力,显微镜(AFM)对EAFP晶体的{100}面进行动态的生长研究,发现在中低过饱和度下主要以各向异性的单双链螺旋位错的生长模式进行生长,详细研究了这种螺旋的形成机制,并探讨了其结构基础.     

天花粉蛋白晶体生长的斜锥形成核机制

用原子力显微镜(AFM)研究了天花粉蛋白(Trichosanthin,TCS)晶体表面的斜锥形成核过程.对不同过饱和度下(σ=1.02～1.65)的TCS晶体成核过程进行了全方位的跟踪观察.发现在结晶前期,体系先采用线型生长,生长成链状聚集体,再进行侧向链间结合,最后形成不对称三维斜锥形核;在后期的成核过程中,TCS分子以尺寸不一的球形聚集体存在,并依次连接成串,进一步形成斜锥形核.通过AFM实验,详实地观测了TCS晶体生长的斜锥形成核过程,并从结构生物学角度阐释了这一成核现象的微观机制,给出了两种的成核途径.     

Chemical identification of individual surface atoms by atomic force microscopy

Scanning probe microscopy is a versatile and powerful method that uses sharp tips to image, measure and manipulate matter at surfaces with atomic resolution. At cryogenic temperatures, scanning probe microscopy can even provide electron tunnelling spectra that serve as fingerprints of the vibrational properties of adsorbed molecules and of the electronic properties of magnetic impurity atoms, thereby allowing chemical identification. But in many instances, and particularly for insulating systems, determining the exact chemical composition of surfaces or nanostructures remains a considerable challenge. In principle, dynamic force microscopy should make it possible to overcome this problem: it can image insulator, semiconductor and metal surfaces with true atomic resolution, by detecting and precisely measuring the short-range forces that arise with the onset of chemical bonding between the tip and surface atoms and that depend sensitively on the chemical identity of the atoms involved. Here we report precise measurements of such short-range chemical forces, and show that their dependence on the force microscope tip used can be overcome through a normalization procedure. This allows us to use the chemical force measurements as the basis for atomic recognition, even at room temperature. We illustrate the performance of this approach by imaging the surface of a particularly challenging alloy system and successfully identifying the three constituent atomic species silicon, tin and lead, even though these exhibit very similar chemical properties and identical surface position preferences that render any discrimination attempt based on topographic measurements impossible.     

利用原子力显微镜表征页岩孔隙结构特征

页岩储层孔隙结构复杂,非均质性强,矿物组分多样,这些储层特性加大了页岩油的开采难度。为了更好地表征页岩孔隙结构,利用原子力显微镜(atomic force microscope, AFM)技术,结合Gwyddion软件对大港、吉木萨尔和松辽盆地页岩的孔隙结构以及表面粗糙度进行了表征。结合快速傅里叶变换(fast Fourier transform, FFT)分析页岩的非均质性,采用分水岭法识别孔隙分布特征,分析不同地区页岩储层的孔隙结构差异。原子力显微镜可以对页岩的表面形貌进行表征,通过平均粗糙度、均方粗糙度、表面偏度和峰度系数等参数对表面粗糙度进行评价,可以准确表征页岩纳米级的孔隙结构,包括孔隙数量、孔隙大小、孔隙面积、孔隙体积和孔隙度等。结果表明：大港和吉木萨尔页岩的表面高度较高,松辽盆地页岩表面高度较低,大港页岩非均质性较强,孔隙主要以微孔为主,吉木萨尔页岩和松辽盆地页岩非均质性较弱,中孔和宏孔数量较多,孔隙发育较好。     

Transmission electron microscopy and atomic force microscopy characterization of nickel deposition on bacterial cells

Recently bacterial cells have become attractive biological templates for the fabrication of metal nano- structures or nanomaterials due to their inherent small size, various standard geometrical shapes and abundant source. In this paper, nickel-coated bacterial cells (gram-negative bacteria of Escherichia coli) were fabricated via electroless chemical plating. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) characterization results reveal evident morphological difference between bacterial cells before and after deposition with nickel. The bare cells with smooth surface presented transverse outspreading effect at mica surface. Great changes took place in surface roughness for those bacterial cells after metallization. A large number of nickel nanoparticles were observed to be equably distributed at bacterial surface after activation and subsequent metallization. Furthermore, ultra thin section analytic results validated the presence and uniformity of thin nickel coating at bacte- rial surface after metallization.     

Micro-friction of diazoresin/polyacrylic acid self-assembly films in water with atomic force microscopy

Ultrathin films composed of diazoresin（DR）and polyacrylic acid（PAA）were fabricated.The surface morphology of the films in water was measured using an atomic force microscopy（AFM）.The self-assembly technique makes the surface rather flat and uniform.The friction force and its dependence on the velocity differ from the surface charge of the thin films.The friction force of repulsive DR/PAA film increases linearly with velocity and has lower values than that of attractive DR film over the full range of velocity.As the velocity increases,the attractive friction of DR film first decreases to a minimum at a velocity of 2 line/s and then increases all the way.When the surface is repulsive to the friction substrate,the friction of thin films that is determined by hydrated lubrication of polymer chains that is ultralubricated;when it is adhesive to the friction substrate,the friction is mainly contributed from the elastic deformation of adsorbed polymer chains in the low velocity region and from viscous sliding in the presence of hydrated-layer lubrication of the polymer chains in the higher velocity region.     

Video imaging of walking myosin V by high-speed atomic force microscopy

The dynamic behaviour of myosin V molecules translocating along actin filaments has been mainly studied by optical microscopy. The processive hand-over-hand movement coupled with hydrolysis of adenosine triphosphate was thereby demonstrated. However, the protein molecules themselves are invisible in the observations and have therefore been visualized by electron microscopy in the stationary states. The concomitant assessment of structure and dynamics has been unfeasible, a situation prevailing throughout biological research. Here we directly visualize myosin V molecules walking along actin tracks, using high-speed atomic force microscopy. The high-resolution movies not only provide corroborative 'visual evidence' for previously speculated or demonstrated molecular behaviours, including lever-arm swing, but also reveal more detailed behaviours of the molecules, leading to a comprehensive understanding of the motor mechanism. Our direct and dynamic high-resolution visualization is a powerful new approach to studying the structure and dynamics of biomolecules in action.     

Application of atomic force microscopy to living samples from cells to fresh tissues

Atomic force microscopy is a novel method for imaging and characterization in biomedicine. However, high-resolution imaging of living samples from cells to tissues still remains a challenge. In this paper, two types of AFM working mode （contact mode and tapping mode） which are utilized for the imaging of living cells and tissues are discussed. A new magnetic tapping mode （MAC mode）, which is more suitable for living samples, and a novel data collecting system named TREC, are also introduced.     

Mapping CD20 molecules on the lymphoma cell surface using atomic force microscopy

Atomic force microscopy (AFM) was used to locate CD20 molecules on the surface of lymphoma Raji cells. Rituximab (a monoclonal antibody against CD20) molecules were linked onto the AFM tip via a polyethylene glycol (PEG) linker. Raji cells were adsorbed onto glass slides coated with poly-L-lysine. First, the CD20 distribution in a local area of the cell surface was visualized using the AFM lift scan mode. Second, 16 × 16 force curves were obtained from the same cell area to construct the CD20-rituximab binding force map. Finally, free rituximab was added to block the CD20 molecules on the cell surface and the lift phase image and CD20-rituximab force map were obtained again. The experimental results indicated that when the lift height was greater than the length of the PEG linker, no recognition sites were observed in the lift phase image. However, as the lift height decreased to the length of the PEG linker, some recognition sites were observed in the lift phase image and these sites were generally consistent with the pixels in the force map. After blocking, both the recognition sites in the lift phase image and the gray pixels in the binding force map decreased markedly. These results can improve our understanding of the distribution of protein molecules on the cell surface and facilitate further investigations into cellular functions.     

原子力显微镜针尖在试样表面滑动的力学模型

建立了原子力显微镜针尖在试样表面滑动的力学模型，并通过实验进行了验证。结果表明，粒子间距变大使摩擦力曲线的周期变大，振幅变小；作用势V0反映的是表面自由能的大小，V0增大，摩擦力曲线的振幅变大；阻尼反映的是速度对摩擦力的影响，阻尼变小，摩擦力曲线的振幅基本保持不变，曲线整体下移，但幅度较小。在一定范围内速度对摩擦力的影响不大。     

Numerical surface characterization of wear debris from artificial joints using atomic force microscopy

Study on surface features of wear particles generated in wear process provides an insight into the progress of material failure of artificial joints. It is very important to quantify the surface features of wear particles in three dimensions. In this study, a new approach using atomic force microscopy was proposed to carry out 3D numerical surface characterization of wear debris generated from artificial joints. Atomic force microscopy combined with image processing techniques was used to acquire appropriate 3D images of wear debris. Computerized image analysis techniques were then used to quantify surface texture features of wear debris such as surface roughness parameters and surface texture index. The method developed from the present study was found to be feasible to quantity the surface characterization of nanoand micro-sized wear debris generated from artificial joints.     

利用原子力显微镜研究晶体缺陷

首次利用原子力显微镜研究晶体表面缺陷，给出了经腐蚀后的KTiOAsO4晶体表面铁电畴和位错蚀坑的清晰照片和定量信息。对实验结果和方法进行了讨论。指出这种实验方法具有放大倍数高，分辨率可达原子量级，可以给出物质表面结构的定量信息和立体图像等特点，并且具体探讨了利用原子力显微镜研究晶体表面缺陷的一些实验技术问题。