| Several imaging factors of atomic force microscope (AFM) were explored. The adsorption and self-assembly of collagen molecules on the mica surface were studied by AFM. Murine embryonic stem(ES) cells and red blood cells were also imaged by AFM . The morphology of single cell and the ultrastructure of cell membrane were observed . By means of AFM, the ultra-thin sections of murine ES cells were investigated in order to make AFM capable of gaining the information of the inner structure of cells. In addition, the morphological changes and damaging effect of trichosanthin (TCS) on red blood cell (RBC) membrane were observed by AFM.Surface roughness of four routine substrates for AFM were measured and the methods of preparing biological samples were tried and concluded. The results showed that for biological macromolecules (for example collagen) the best images could be gained when the substrate was mica dealt with MgCl2. With regard to cells , the ordinary coverslips were suitable to gain stable AFM images. A damaging phenomenon of AFM tip to collagen fibril was studied to optimize the imaging factors of AFM.The adsorption and self-assembly of collagen solutions (type I , from calf skin) on the mica surface were studied by AFM. The mica surface was dealt with Mg2+. By changing the concentration and pH, the self-assembly behavior of collagen molecules under different conditions was investigated .By means of the high resolution of AFM, the self-assembly of collagen molecules on mica surface was directly observed on the nanometer scale .With AFM and TEM, the inner ultrastructure of murine ES cells could be observed .Combined with the technique of ultra-thin sections, AFM is capable of studying the inner structure of sample .Red blood cells were imged by AFM and the typical biconcave shapes were observed . The ultrastructure of RBC membrane was also gained. Themorphological changes of red blood cell (RBC) membrane after the interaction of trichosanthin (TCS) were clearly observed by AFM.
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