Development and Application of Atomic Force Microscopy to biological sciences.

原子力显微镜（AFM）（JSTM-4200 A，JEOL）是扫描探针显微镜的一种，被引入到生物应用技术的发展中。AFM采用接触式装置，在室温空气中，将氮化硅探针置于悬臂梁顶端，在样品表面进行扫描。由于原子力显微镜最初是为材料科学而设计的，为了更好地接近生物材料，对某些部件或装置进行了改进，并开发了新的生物样品制备方法，尝试在原子力显微镜下观察生物样品。虽然10 nm左右的厚度并不被认为是正确的数量级，但这种方法将有助于分析分子间的相互作用。对某些类型的上皮细胞表面的观察显示了在空气中高倍放大的清晰的微绒毛和微皱襞图像，而没有SEM观察所需的金属涂层。冷冻干燥法是制备样品的有效方法，与传统显微镜相比，AFM的优点是在空气中观察分辨率高，易于接近，即使在潮湿条件下也可操作，分子和细胞比在干燥条件下保持更多的功能结构。原子力显微镜将为生物材料的观察提供一种新的有用的方法。

The atomic force microscope (AFM) (JSTM-4200A,JEOL), one of subtypes of scanning probe microscopes, was introduced to develop techniques for biological applications. The AFM is equipped with contact mode device in which a silicon-nitride probe at the tip of cantilever scan over the surface of specimens in the air at room temperature. As the AFM is originally designed for material sciences, some parts or devices were modified in order to obtain better accessibility for biological materials.New preparation procedures of biological specimens were also developed and attempted for observation under AFM.Purified plasmid DNA resuspended in double distillled water were bound on the freshly cleaved mica surface, and a circular profile of DNA molecules was visualized under AFM.Although the thickness measured about 10 nm is not considered to be correct order, the accessibility of this method will be facilitated for analysis of molecular interactions. Observation of some types of epithelial cell surface revealed clear images of microvilli and microplicae with high magnification in the air, without metal coating which is required for SEM observation. Freeze-drying is proved to be effective for preparation of specimens.The advantages of AFM over conventional microscopy are observation of high resolution in the air, easy accessibility, and to be operable even in wet condition in which moleculea and cell maintain more functional structure than in dry condition. The AFM will provide a new useful method for the observation of biological materials.