Dispersion of a solid particle in water may lead to the formation of hydration film on the particle surface, which can strongly increase the repulsive force between the particles and thus strongly affect the stability...Dispersion of a solid particle in water may lead to the formation of hydration film on the particle surface, which can strongly increase the repulsive force between the particles and thus strongly affect the stability of dispersions. The hydration film thickness, which varies with the variation of property of suspension particles, is one of the most impor- tant parameters of hydration film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on force-distance curve of atomic force microscopy, for determining the hydration film thick- ness of particles is developed. The method utilizes the differ- ence of cantilever deflection before, between and after pene- trating the hydration films between tip and sample, which reflect the difference of slope on the force-distance curve. 3 samples, mica, glass and stainless steel, were used for hydra- tion thickness determination, and the results show that the hydration film thickness between silicon tip and mica, glass and stainless steel are 30.0±2.0, 29.0±1.0 and 32.5±2.5 nm, respectively.展开更多
The spider dragline silk has excellent mechanical properties. The stress- strain curves of dragline silk fibers have intraspecific and intraindividual variability because of the spider’s active control during spinnin...The spider dragline silk has excellent mechanical properties. The stress- strain curves of dragline silk fibers have intraspecific and intraindividual variability because of the spider’s active control during spinning process. To investigate the relationship between the morphology of dragline silk fibers and spinning conditions, four samples were made at the reeling rates of 1 mm/s, 20 mm/s, 43.5 mm/s and 110 mm/s from the major ampullate glands of Araneus Ventricosus and the other two of dragline silks were prepared from a crawling or dropping spider. The surface microstructure and nanofibril characteristic were analyzed with atomic force microscopy (AFM). AFM images of 2 000 nm *2 000 nm and 500 nm*500 nm of these samples showed that the spinning condition influenced the surface roughness and fibril size, while AFM images of 200 nm*200 nm clearly displayed that dragline silk of Araneus Ventricosus included sheet macro-conformation structure. These results can facilitate the further investigation of the spinning mechanism of a spider in order to understand mechanical properties and macromolecular structures of dragline silk.展开更多
The mesostructure at the cross section of the Fe-based nanocrystalline (Fe73.5Cu1Nb3Si13.5B9) ribbon was observed with atomic force microscopy (AFM). An apparent mesostructural difference was found between the stickin...The mesostructure at the cross section of the Fe-based nanocrystalline (Fe73.5Cu1Nb3Si13.5B9) ribbon was observed with atomic force microscopy (AFM). An apparent mesostructural difference was found between the sticking roller face area (SRFA) and the free face area (FFA) of the ribbon crystallized after annealing. In SRFA there is a pre-ponderance of rough grain gathering in longitudinal ar-rangement, while in FFA a fine grain gathering arranged transversely dominates. This phenomenon could be due to the different residual stress remained in the different areas of the amorphous ribbon resulting from the single-roller quenching technique.展开更多
Cell-free system is interesting and useful for studying nuclear assembly in mitosis. Atomic force micro- scopy (AFM), which is a simple way for imaging fixed reas-semble nuclei with high resolution, has not been used ...Cell-free system is interesting and useful for studying nuclear assembly in mitosis. Atomic force micro- scopy (AFM), which is a simple way for imaging fixed reas-semble nuclei with high resolution, has not been used in the cell-free system. In this paper, we put forward an air-drying sample preparation for AFM. Using AFM, we observed nu-clear reassembly process within 100 nm resolution in a cell-free system. As a result, we found that the images were artifact-free, and with higher resolution compared with fluo-rescent optical microscope images. Furthermore, the mor-phology of membrane vesicles was obtained clearly, and a dynamic change of morphology during the vesicles?ap-proaching to nuclear envelope was also observed, which is enlightened to understand the mechanism of nuclear enve-lope assembly.展开更多
The insoluble and fibrillar aggregates of some proteins are thought to be the pathological cause of neu- rodegenerative diseases. The aggregation-propensities of different types of proteins were investigated by Thiofl...The insoluble and fibrillar aggregates of some proteins are thought to be the pathological cause of neu- rodegenerative diseases. The aggregation-propensities of different types of proteins were investigated by Thioflavine T fluorescence assay and atomic force microscopy imaging. Then, the structural transformations of the proteins from aqueous state to solid state were studied by circular dichroism spectroscopy. The results indicate that proteins of dif- ferent secondary structure show variations in their aggregation-propensities, together with their various structural transformations from aqueous state to solid state. Our studies imply that the structural transformation of proteins from solution to solid state is closely associated with their aggregation-propensities, which will provide insight into the molecular mechanism of protein aggregation in neurodegenerative diseases.展开更多
文摘Dispersion of a solid particle in water may lead to the formation of hydration film on the particle surface, which can strongly increase the repulsive force between the particles and thus strongly affect the stability of dispersions. The hydration film thickness, which varies with the variation of property of suspension particles, is one of the most impor- tant parameters of hydration film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on force-distance curve of atomic force microscopy, for determining the hydration film thick- ness of particles is developed. The method utilizes the differ- ence of cantilever deflection before, between and after pene- trating the hydration films between tip and sample, which reflect the difference of slope on the force-distance curve. 3 samples, mica, glass and stainless steel, were used for hydra- tion thickness determination, and the results show that the hydration film thickness between silicon tip and mica, glass and stainless steel are 30.0±2.0, 29.0±1.0 and 32.5±2.5 nm, respectively.
基金science and technology office of Jiangsu province
文摘The spider dragline silk has excellent mechanical properties. The stress- strain curves of dragline silk fibers have intraspecific and intraindividual variability because of the spider’s active control during spinning process. To investigate the relationship between the morphology of dragline silk fibers and spinning conditions, four samples were made at the reeling rates of 1 mm/s, 20 mm/s, 43.5 mm/s and 110 mm/s from the major ampullate glands of Araneus Ventricosus and the other two of dragline silks were prepared from a crawling or dropping spider. The surface microstructure and nanofibril characteristic were analyzed with atomic force microscopy (AFM). AFM images of 2 000 nm *2 000 nm and 500 nm*500 nm of these samples showed that the spinning condition influenced the surface roughness and fibril size, while AFM images of 200 nm*200 nm clearly displayed that dragline silk of Araneus Ventricosus included sheet macro-conformation structure. These results can facilitate the further investigation of the spinning mechanism of a spider in order to understand mechanical properties and macromolecular structures of dragline silk.
文摘The mesostructure at the cross section of the Fe-based nanocrystalline (Fe73.5Cu1Nb3Si13.5B9) ribbon was observed with atomic force microscopy (AFM). An apparent mesostructural difference was found between the sticking roller face area (SRFA) and the free face area (FFA) of the ribbon crystallized after annealing. In SRFA there is a pre-ponderance of rough grain gathering in longitudinal ar-rangement, while in FFA a fine grain gathering arranged transversely dominates. This phenomenon could be due to the different residual stress remained in the different areas of the amorphous ribbon resulting from the single-roller quenching technique.
基金supported by the National Natural Science Foundation of China(Grant Nos.19890380 and 30070388)the Special Funds for the Major State Bask Research of China(Grant No.G19990539).
文摘Cell-free system is interesting and useful for studying nuclear assembly in mitosis. Atomic force micro- scopy (AFM), which is a simple way for imaging fixed reas-semble nuclei with high resolution, has not been used in the cell-free system. In this paper, we put forward an air-drying sample preparation for AFM. Using AFM, we observed nu-clear reassembly process within 100 nm resolution in a cell-free system. As a result, we found that the images were artifact-free, and with higher resolution compared with fluo-rescent optical microscope images. Furthermore, the mor-phology of membrane vesicles was obtained clearly, and a dynamic change of morphology during the vesicles?ap-proaching to nuclear envelope was also observed, which is enlightened to understand the mechanism of nuclear enve-lope assembly.
基金Supported by the National Natural Science Foundation of China (No. 30070165) Science & Technology Committee of Shanghai+1 种基金 (No.0159NM078 No.03JC14081).
文摘The insoluble and fibrillar aggregates of some proteins are thought to be the pathological cause of neu- rodegenerative diseases. The aggregation-propensities of different types of proteins were investigated by Thioflavine T fluorescence assay and atomic force microscopy imaging. Then, the structural transformations of the proteins from aqueous state to solid state were studied by circular dichroism spectroscopy. The results indicate that proteins of dif- ferent secondary structure show variations in their aggregation-propensities, together with their various structural transformations from aqueous state to solid state. Our studies imply that the structural transformation of proteins from solution to solid state is closely associated with their aggregation-propensities, which will provide insight into the molecular mechanism of protein aggregation in neurodegenerative diseases.
