Proteins play a vital role in different biological processes by forming complexes through precise folding with exclusive inter-and intra-molecular interactions.Understanding the structural and regulatory mechanisms un...Proteins play a vital role in different biological processes by forming complexes through precise folding with exclusive inter-and intra-molecular interactions.Understanding the structural and regulatory mechanisms underlying protein complex formation provides insights into biophysical processes.Furthermore,the principle of protein assembly gives guidelines for new biomimetic materials with potential appli-cations in medicine,energy,and nanotechnology.Atomic force microscopy(AFM)is a powerful tool for investigating protein assembly and interactions across spatial scales(single molecules to cells)and temporal scales(milliseconds to days).It has significantly contributed to understanding nanoscale architectures,inter-and intra-molecular interactions,and regulatory elements that determine protein structures,assemblies,and functions.This review describes recent advancements in elucidating protein assemblies with in situ AFM.We discuss the structures,diffusions,interac-tions,and assembly dynamics of proteins captured by conventional and high-speed AFM in near-native environments and recent AFM developments in the multimodal high-resolution imaging,bimodal imaging,live cell imaging,and machine-learning-enhanced data analysis.These approaches show the significance of broadening the horizons of AFM and enable unprecedented explorations of protein assembly for biomaterial design and biomedical research.展开更多
Two-dimensional(2D)materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties,making them a focal point in nanotechnology research.Accurate assessment ...Two-dimensional(2D)materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties,making them a focal point in nanotechnology research.Accurate assessment of the mechanical and tribological properties of 2D materials is imperative to fully exploit their potential across diverse applications.However,their nanoscale thickness and planar nature pose significant challenges in testing and characterizing their mechanical properties.Among the in situ characterization techniques,atomic force microscopy(AFM)has gained widespread applications in exploring the mechanical behaviour of nanomaterials,because of the easy measurement capability of nano force and displacement from the AFM tips.Specifically,AFM-based force spectroscopy is a common approach for studying the mechanical and tribological properties of 2D materials.This review comprehensively details the methods based on normal force spectroscopy,which are utilized to test and characterize the elastic and fracture properties,adhesion,and fatigue of 2D materials.Additionally,the methods using lateral force spectroscopy can characterize the interfacial properties of 2D materials,including surface friction of 2D materials,shear behaviour of interlayers as well as nanoflake-substrate interfaces.The influence of various factors,such as testing methods,external environments,and the properties of test samples,on the measured mechanical properties is also addressed.In the end,the current challenges and issues in AFM-based measurements of mechanical and tribological properties of 2D materials are discussed,which identifies the trend in the combination of multiple methods concerning the future development of the in situ testing techniques.展开更多
The organization of the higher order structure of chromatin in chicken erythrocytes has been examined withtapping-mode scanning force microscopy under conditionsclose to their native environment. Reproducible highreso...The organization of the higher order structure of chromatin in chicken erythrocytes has been examined withtapping-mode scanning force microscopy under conditionsclose to their native environment. Reproducible highresolution AFM images of chromatin compaction at several levels can be demonstrated. An extended beads-on-astring (width of ~ 15-20nm, height of ~ 2-3nm for eachindividual nucleosome) can be consistently observed. Furthermore, superbeads (width of ~ 40nm, height of ~ 7nm)are demonstrated. Visualization of the solenoid conformation at the level of 30nm chromatin fiber is attained eitherby using AFM or by using electron microscopy. In addition, tightly coiled chromatin fibers (~ 50-60nm and ~90-110nm) can be revealed. Our data suggest that the chromatin in the interphase nucleus of chicken erythrocyte represents a high-order conformation and AFM provides useful high-resolution structural information concerning thefolding pattern of interphase chromatin fibers.展开更多
An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy (AFM) here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two hig...An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy (AFM) here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function. Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication's difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.展开更多
The microstructure of asphalt is investigated by atomic force microscopy (AFM). In order to analyze the impacts of asphalt types on microstructures, two neat asphalts with different penetration grades (50# and 70#...The microstructure of asphalt is investigated by atomic force microscopy (AFM). In order to analyze the impacts of asphalt types on microstructures, two neat asphalts with different penetration grades (50# and 70#) and one styrene-butadiene-styrene (SBS) modified asphalt are chosen. The influence of short-term aging is also studied. Based on the knowledge of asphalt's microproperties, the relationship between microstructures and healing property is analyzed. The results indicate that the microstructures of three asphalts are quite different and the effects of aging on the surface characteristics for different asphalts are also different. It is proposed that the bee structure is a type of wax crystal and it has a close relationship with the "bridge-healing" mechanism. The findings may reveal the formation mechanism of microstructure and the healing property for asphalts.展开更多
DNA and histone protein are important in the formation of nucleosomal arrays, which are the first packaging level of DNA into a more compact chromatin structure. To characterize the interactions of DNA and histone pro...DNA and histone protein are important in the formation of nucleosomal arrays, which are the first packaging level of DNA into a more compact chromatin structure. To characterize the interactions of DNA and histone proteins, we reconstitute nucleosomes using lambda DNA and whole histone proteins by dialysis and perform direct atomic force microscopy (AFM) imaging. Compared with non-specific DNA and histone binding, nucleosomes are formed within the assembled “beads-on-a-string” nucleosomal array by dialysis. These observations facilitate the establishment of the molecular mechanisms of nucleosome and demonstrate the capability of AFM for protein-DNA interaction analysis.展开更多
By using tapping mode atomic force microscopy(TMAFM), a polymer layer was found on the enamel surface after the exposure to xanthan gum solutions. The layer thickness is closely related to the exposure time and the co...By using tapping mode atomic force microscopy(TMAFM), a polymer layer was found on the enamel surface after the exposure to xanthan gum solutions. The layer thickness is closely related to the exposure time and the concentration of xanthan gum solution. The thickness data were evaluated by a Kruskal-Wallis test and Box-Whisker Plot at a 95% confidence level(p<0.05), and a statistically significant difference among the thickness data groups was demonstrated. After the exposure to 1000, 400, 100 mg/L xanthan gum solutions, the mean of layer thickness at the adsorption equilibrium is in the ranges of 103.5_122.06, 82.4_88.94 and 45.27_55.55 nm, respectively. This phenomenon suggests that the viscosity modifying agents in the beverage might be adsorbed on the enamel surface during consumption, which may form a barrier that can protect the enamel from being attacked by acid and therefore reduce dental erosion.展开更多
Aggregation process of isotactic poly(methyl methacrylate) (i-PMMA) has been studied extensively for many years, and considerable progress has been made in both experimental and theoretical studies. They are, howe...Aggregation process of isotactic poly(methyl methacrylate) (i-PMMA) has been studied extensively for many years, and considerable progress has been made in both experimental and theoretical studies. They are, however, seldom sustained by real-space observations of the underlying morphology. In this paper, the aggregation process of i-PMMA in concentrated acetone solutions and the fractal structure of the resulting three-dimensional clusters were characterized on the basis of real-space AFM observations of their two-dimensional projection. It was found that spherical multiple-chain particles formed upon collapse and aggregation of the involving chains as a whole during quenching the solution to room temperature. By keeping the solution at room temperature, the initially formed particles stick together upon contact to form larger particles through reassembling very slowly. The succeeding collision of the enlarged spherical particles leads to the formation of small clusters. These newly formed small clusters grow when they meet with other clusters or single Brownian particles. This leads to the formation of large clusters with fractal dimension of 1.95 ± 0.05, which suggest a reaction-limited cluster aggregation of i-PMMA in a concentrated acetone solution. This is in accordance with the conclusion obtained by light scattering measurements.展开更多
In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy (AFAM) in which the sample is vibrated a...In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy (AFAM) in which the sample is vibrated at the ultrasonic frequency while the sample surface is touched and scanned with the tip contacting the sample respectively for fixed point and continuous measurements. The SiOx films on the silicon wafers are prepared by the plasma enhanced chemical vapour deposition (PECVD), The local contact stiffness of the tip-SiOx film is calculated from the contact resonance spectrum measured with the atomic force acoustic microscopy. Using the reference approach, indentation modulus of SiOx film for fixed point is obtained. The images of cantilever amplitude are also visualized and analysed when the SiOx surface is excited at a fixed frequency. The results show that the acoustic amplitude images can reflect the elastic properties of the sample.展开更多
The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the spe...The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the specific nanostructural information of a new antitumor drug binding to DNA.展开更多
Through the investigation of the sample surface and interface of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA)/indium-tin-oxide (ITO) thin films using atomic force microscopy, it has been found that the ...Through the investigation of the sample surface and interface of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA)/indium-tin-oxide (ITO) thin films using atomic force microscopy, it has been found that the surface is complanate, the growth is uniform and the defects cover basically the surface of ITO. Furthermore, the number of pinholes is small. The analysis of the sample surface and interface further verifies this result by using x-ray photoemission spectroscopy. At the same time, PTCDA is found to have the ability of restraining the diffusion of chemical constituents from ITO to the hole transport layer, which is beneficial to the improvement of the performance and the useful lifetime of the organic light emitting diodes (OLEDs).展开更多
Nanomanipulation of DNA molecules or other biomolecules to form artificial patterns or structures at nanometer scale has potential applications in the construction of molecular devices in future industries. It may als...Nanomanipulation of DNA molecules or other biomolecules to form artificial patterns or structures at nanometer scale has potential applications in the construction of molecular devices in future industries. It may also lead to new insights into the interesting properties and behavior of this fantastic nature-selected molecule at the sin- gle-molecular level. Here we present a special method based on the combination of macroscopic “molecular comb- ing” and microscopic “molecular cutting” to manipulate DNA molecules and form complex patterns at nanometer scale on solid surfaces. A possible strategy for ordered DNA sequencing based on this nanomanipulation technique has also been proposed.展开更多
Hippocampal neurons of neonatal rats were cultured in serum-free culture medium for 5 days in vitro, and treated with the Rho-kinase inducer lysophosphatidic acid. Atomic force microscopy revealed that the numbers of ...Hippocampal neurons of neonatal rats were cultured in serum-free culture medium for 5 days in vitro, and treated with the Rho-kinase inducer lysophosphatidic acid. Atomic force microscopy revealed that the numbers of level-1, -2 and -3 neurites protruding from rat hippocampal neurons was significantly reduced. After treatment with the Rho kinase inhibitor Y27632, a significant increase in the numbers of these neurites was observed. Our experimental findings indicate that the Rho-kinase pathway is closely associated with the neurites of hippocampal neurons.展开更多
An efficient method based on atomic force microscopy(AFM) has been developed to characterize silicon intercalated graphene grown on single crystalline Ir(111) thin films. By combining analyses of the phase image, ...An efficient method based on atomic force microscopy(AFM) has been developed to characterize silicon intercalated graphene grown on single crystalline Ir(111) thin films. By combining analyses of the phase image, force curves,and friction–force mapping, acquired by AFM, the locations and coverages of graphene and silicon oxide can be well distinguished. We can also demonstrate that silicon atoms have been successfully intercalated between graphene and the substrate. Our method gives an efficient and simple way to characterize graphene samples with interacted atoms and is very helpful for future applications of graphene-based devices in the modern microelectronic industry, where AFM is already widely used.展开更多
The structure of the nuclosome core particle of chromatin in chicken erythrocytes has been examined by usingAFM. The 146 hp of DNA wrapped twice around the corehistone octamer are clearly visualized. Both the ends ofe...The structure of the nuclosome core particle of chromatin in chicken erythrocytes has been examined by usingAFM. The 146 hp of DNA wrapped twice around the corehistone octamer are clearly visualized. Both the ends ofentry/exit of linker DNA are also demonstrated. The dimension of the nucleosome core particles is- 1-4 um inheight and ~13-22 um in width. In addition, superbeads(width of - 48-57 urn, beight of-2-3 nm) are occasionallyrevealed, two turns of DNA around the core particles arealso detected.展开更多
Bone marrow mesenchymal stem cells (MSCs) from rats were transfected with Rn-siRNA-caveolin-1 and differentiated into neuron-like cells using fasudil hydrochloride. Membrane ultrastructural changes in MSCs were obse...Bone marrow mesenchymal stem cells (MSCs) from rats were transfected with Rn-siRNA-caveolin-1 and differentiated into neuron-like cells using fasudil hydrochloride. Membrane ultrastructural changes in MSCs were observed under atomic force microscopy. Caveolin-l-transfected rat MSCs exhibited weak nuclear refraction, dense caveolae and long finger-like cellular processes prior to fasudil hydrochloride treatment. MSCs differentiating into neuron-like cells exhibited weak nuclear refraction and large cellular processes without caveolae. We hypothesize that caveolin-1 plays an important role in the regulation of bone marrow MSC differentiating into neuron-like cells.展开更多
We investigated microstructure morphologies of three asphalts(SK, Karamay, and Esso) used in China using atomic force microscopy(AFM). The topography and phase contrast images were obtained. Topographic profile an...We investigated microstructure morphologies of three asphalts(SK, Karamay, and Esso) used in China using atomic force microscopy(AFM). The topography and phase contrast images were obtained. Topographic profile and three dimensional images were described. Roughnesses of microstructure were calculated. And the chemical compositions of asphalt were tested to explain the microstructural mechanism of the asphalt. The results show that the topography and phase image in atomic force microscopy are appropriate to evaluate the microstructure of the asphalt binder. There are significant differences in microstructural morphologies including bee-like structure, topographic profile, 3D image, and roughness for three asphalts in this study. There are three different phases in microstructure of asphalt binder. The oil source and chemical composition of asphalt, especially asphaltenes content have a great influence on the microstructure.展开更多
AIM: To find suitable solutions having lesser granules and keeping erythrocytes in normal shapes under atomic force microscopy (AFM). METHODS: Eight kinds of solutions, 1% formaldehyde, PBS buffer (pH7.2), citrate buf...AIM: To find suitable solutions having lesser granules and keeping erythrocytes in normal shapes under atomic force microscopy (AFM). METHODS: Eight kinds of solutions, 1% formaldehyde, PBS buffer (pH7.2), citrate buffer (pH6.0), 0.9% NaCl, 5% dextrose, TAE, 1640 medium and 5% EDTA-K2, were selected from commonly used laboratory solutions, and venous blood from a healthy human volunteer was drawn and anticoagulated with EDTA-K2. Before scanned by AFM (NanoScopeIIIa SPM, Digital Instruments, Santa Barbara, CA), a kind of intermixture was deposited on freshly cleaved mica and then dried in the constant temperature cabinet (37 ℃). RESULTS: One percent formaldehyde, citrate buffer, 5% dextrose, TAE, were found to keep human erythrocytes in normal shape with few particles. Processed by these solutions, fine structures of human erythrocyte membrane were obtained. CONCLUSION: One percent formaldehyde, citrate buffer, 5% dextrose and TAE may be applied to dispose erythrocytes in AFM. The results may offer meaningful data for clinical diagnosis of blood by AFM.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:32371525,T2221001,92353304,T2350011Strategic Priority Research Program of the Chinese Academy of Sciences,Grant/Award Number:XDB37020105+5 种基金U.S.Department of EnergyOffice of ScienceOffice of Basic Energy Sciences,Grant/Award Number:FWP 65357Pacific Northwest National LaboratoryEnergy Frontier Research CentersCenter for the Science of Synthesis Across Scales,Grant/Award Number:DE-SC0019288。
文摘Proteins play a vital role in different biological processes by forming complexes through precise folding with exclusive inter-and intra-molecular interactions.Understanding the structural and regulatory mechanisms underlying protein complex formation provides insights into biophysical processes.Furthermore,the principle of protein assembly gives guidelines for new biomimetic materials with potential appli-cations in medicine,energy,and nanotechnology.Atomic force microscopy(AFM)is a powerful tool for investigating protein assembly and interactions across spatial scales(single molecules to cells)and temporal scales(milliseconds to days).It has significantly contributed to understanding nanoscale architectures,inter-and intra-molecular interactions,and regulatory elements that determine protein structures,assemblies,and functions.This review describes recent advancements in elucidating protein assemblies with in situ AFM.We discuss the structures,diffusions,interac-tions,and assembly dynamics of proteins captured by conventional and high-speed AFM in near-native environments and recent AFM developments in the multimodal high-resolution imaging,bimodal imaging,live cell imaging,and machine-learning-enhanced data analysis.These approaches show the significance of broadening the horizons of AFM and enable unprecedented explorations of protein assembly for biomaterial design and biomedical research.
基金support from the National Natural Science Foundation of China(Nos.52005151,12172118,52205591,12227801,and 12072005)the Local Science and Technology Development Fund Projects Guided by the Central Government of China(No.236Z1810G)+4 种基金the Natural Science Foundation of Hebei Province(Nos.E2021202008 and E2021202100)the Fund for Innovative Research Groups of Natural Science Foundation of Hebei Province(No.A2020202002)the Key Program of Research and Development of Hebei Province(No.202030507040009)the Project of High-Level Talents Introduction of Hebei Province(No.2021HBQZYCSB009)the Key Project of National Natural Science Foundation of Tianjin(No.S20ZDF077).
文摘Two-dimensional(2D)materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties,making them a focal point in nanotechnology research.Accurate assessment of the mechanical and tribological properties of 2D materials is imperative to fully exploit their potential across diverse applications.However,their nanoscale thickness and planar nature pose significant challenges in testing and characterizing their mechanical properties.Among the in situ characterization techniques,atomic force microscopy(AFM)has gained widespread applications in exploring the mechanical behaviour of nanomaterials,because of the easy measurement capability of nano force and displacement from the AFM tips.Specifically,AFM-based force spectroscopy is a common approach for studying the mechanical and tribological properties of 2D materials.This review comprehensively details the methods based on normal force spectroscopy,which are utilized to test and characterize the elastic and fracture properties,adhesion,and fatigue of 2D materials.Additionally,the methods using lateral force spectroscopy can characterize the interfacial properties of 2D materials,including surface friction of 2D materials,shear behaviour of interlayers as well as nanoflake-substrate interfaces.The influence of various factors,such as testing methods,external environments,and the properties of test samples,on the measured mechanical properties is also addressed.In the end,the current challenges and issues in AFM-based measurements of mechanical and tribological properties of 2D materials are discussed,which identifies the trend in the combination of multiple methods concerning the future development of the in situ testing techniques.
文摘The organization of the higher order structure of chromatin in chicken erythrocytes has been examined withtapping-mode scanning force microscopy under conditionsclose to their native environment. Reproducible highresolution AFM images of chromatin compaction at several levels can be demonstrated. An extended beads-on-astring (width of ~ 15-20nm, height of ~ 2-3nm for eachindividual nucleosome) can be consistently observed. Furthermore, superbeads (width of ~ 40nm, height of ~ 7nm)are demonstrated. Visualization of the solenoid conformation at the level of 30nm chromatin fiber is attained eitherby using AFM or by using electron microscopy. In addition, tightly coiled chromatin fibers (~ 50-60nm and ~90-110nm) can be revealed. Our data suggest that the chromatin in the interphase nucleus of chicken erythrocyte represents a high-order conformation and AFM provides useful high-resolution structural information concerning thefolding pattern of interphase chromatin fibers.
基金This project is supported by National Natural Science Foundation of China (No.50205006).
文摘An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy (AFM) here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function. Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication's difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.
基金The Ph.D.Programs Foundation of Ministry of Education of China(No.20120092110053)
文摘The microstructure of asphalt is investigated by atomic force microscopy (AFM). In order to analyze the impacts of asphalt types on microstructures, two neat asphalts with different penetration grades (50# and 70#) and one styrene-butadiene-styrene (SBS) modified asphalt are chosen. The influence of short-term aging is also studied. Based on the knowledge of asphalt's microproperties, the relationship between microstructures and healing property is analyzed. The results indicate that the microstructures of three asphalts are quite different and the effects of aging on the surface characteristics for different asphalts are also different. It is proposed that the bee structure is a type of wax crystal and it has a close relationship with the "bridge-healing" mechanism. The findings may reveal the formation mechanism of microstructure and the healing property for asphalts.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (No.11274374), the National Basic Research Program of China (No.2009CB930704), and the Basic Scientific Research Foundation of China Agricultural University (No.2012QJ026).
文摘DNA and histone protein are important in the formation of nucleosomal arrays, which are the first packaging level of DNA into a more compact chromatin structure. To characterize the interactions of DNA and histone proteins, we reconstitute nucleosomes using lambda DNA and whole histone proteins by dialysis and perform direct atomic force microscopy (AFM) imaging. Compared with non-specific DNA and histone binding, nucleosomes are formed within the assembled “beads-on-a-string” nucleosomal array by dialysis. These observations facilitate the establishment of the molecular mechanisms of nucleosome and demonstrate the capability of AFM for protein-DNA interaction analysis.
文摘By using tapping mode atomic force microscopy(TMAFM), a polymer layer was found on the enamel surface after the exposure to xanthan gum solutions. The layer thickness is closely related to the exposure time and the concentration of xanthan gum solution. The thickness data were evaluated by a Kruskal-Wallis test and Box-Whisker Plot at a 95% confidence level(p<0.05), and a statistically significant difference among the thickness data groups was demonstrated. After the exposure to 1000, 400, 100 mg/L xanthan gum solutions, the mean of layer thickness at the adsorption equilibrium is in the ranges of 103.5_122.06, 82.4_88.94 and 45.27_55.55 nm, respectively. This phenomenon suggests that the viscosity modifying agents in the beverage might be adsorbed on the enamel surface during consumption, which may form a barrier that can protect the enamel from being attacked by acid and therefore reduce dental erosion.
基金This work was supported by the National Natural Science Foundations of China.
文摘Aggregation process of isotactic poly(methyl methacrylate) (i-PMMA) has been studied extensively for many years, and considerable progress has been made in both experimental and theoretical studies. They are, however, seldom sustained by real-space observations of the underlying morphology. In this paper, the aggregation process of i-PMMA in concentrated acetone solutions and the fractal structure of the resulting three-dimensional clusters were characterized on the basis of real-space AFM observations of their two-dimensional projection. It was found that spherical multiple-chain particles formed upon collapse and aggregation of the involving chains as a whole during quenching the solution to room temperature. By keeping the solution at room temperature, the initially formed particles stick together upon contact to form larger particles through reassembling very slowly. The succeeding collision of the enlarged spherical particles leads to the formation of small clusters. These newly formed small clusters grow when they meet with other clusters or single Brownian particles. This leads to the formation of large clusters with fractal dimension of 1.95 ± 0.05, which suggest a reaction-limited cluster aggregation of i-PMMA in a concentrated acetone solution. This is in accordance with the conclusion obtained by light scattering measurements.
基金Project supported by the National Natural Science Foundation of China(Grant No.50775005)
文摘In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy (AFAM) in which the sample is vibrated at the ultrasonic frequency while the sample surface is touched and scanned with the tip contacting the sample respectively for fixed point and continuous measurements. The SiOx films on the silicon wafers are prepared by the plasma enhanced chemical vapour deposition (PECVD), The local contact stiffness of the tip-SiOx film is calculated from the contact resonance spectrum measured with the atomic force acoustic microscopy. Using the reference approach, indentation modulus of SiOx film for fixed point is obtained. The images of cantilever amplitude are also visualized and analysed when the SiOx surface is excited at a fixed frequency. The results show that the acoustic amplitude images can reflect the elastic properties of the sample.
基金The support from Visiting Scholar Foundation of Key Lab in University and Chinese Education Foundation for Excellent Young Teachers as well as the support from Jiangsu province (BJ 99011 and BK 2001401) is greatly appreciated.
文摘The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the specific nanostructural information of a new antitumor drug binding to DNA.
基金Project supported by the National Natural Science Foundation of China (Grant No 60276026) and the Natural Science Foundation of Gansu Province, China (Grant No ZS031-A25-012-G).
文摘Through the investigation of the sample surface and interface of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA)/indium-tin-oxide (ITO) thin films using atomic force microscopy, it has been found that the surface is complanate, the growth is uniform and the defects cover basically the surface of ITO. Furthermore, the number of pinholes is small. The analysis of the sample surface and interface further verifies this result by using x-ray photoemission spectroscopy. At the same time, PTCDA is found to have the ability of restraining the diffusion of chemical constituents from ITO to the hole transport layer, which is beneficial to the improvement of the performance and the useful lifetime of the organic light emitting diodes (OLEDs).
基金Supported by National Natural Science Foundation of China (NSFC) under grant No.10335070. Financial support from the Chinese Academy of Sciences and Shanghai Scientific and Technological Committee is also appreciated.
文摘Nanomanipulation of DNA molecules or other biomolecules to form artificial patterns or structures at nanometer scale has potential applications in the construction of molecular devices in future industries. It may also lead to new insights into the interesting properties and behavior of this fantastic nature-selected molecule at the sin- gle-molecular level. Here we present a special method based on the combination of macroscopic “molecular comb- ing” and microscopic “molecular cutting” to manipulate DNA molecules and form complex patterns at nanometer scale on solid surfaces. A possible strategy for ordered DNA sequencing based on this nanomanipulation technique has also been proposed.
文摘Hippocampal neurons of neonatal rats were cultured in serum-free culture medium for 5 days in vitro, and treated with the Rho-kinase inducer lysophosphatidic acid. Atomic force microscopy revealed that the numbers of level-1, -2 and -3 neurites protruding from rat hippocampal neurons was significantly reduced. After treatment with the Rho kinase inhibitor Y27632, a significant increase in the numbers of these neurites was observed. Our experimental findings indicate that the Rho-kinase pathway is closely associated with the neurites of hippocampal neurons.
基金supported by the National Basic Research Program of China(Grant Nos.2013CBA01600 and 2011CB932700)the National Natural Science Foundation of China(Grant Nos.61222112,61390501 and 51325204)Chinese Academy of Sciences(Grant Nos.1731300500015 and XDB07030100)
文摘An efficient method based on atomic force microscopy(AFM) has been developed to characterize silicon intercalated graphene grown on single crystalline Ir(111) thin films. By combining analyses of the phase image, force curves,and friction–force mapping, acquired by AFM, the locations and coverages of graphene and silicon oxide can be well distinguished. We can also demonstrate that silicon atoms have been successfully intercalated between graphene and the substrate. Our method gives an efficient and simple way to characterize graphene samples with interacted atoms and is very helpful for future applications of graphene-based devices in the modern microelectronic industry, where AFM is already widely used.
文摘The structure of the nuclosome core particle of chromatin in chicken erythrocytes has been examined by usingAFM. The 146 hp of DNA wrapped twice around the corehistone octamer are clearly visualized. Both the ends ofentry/exit of linker DNA are also demonstrated. The dimension of the nucleosome core particles is- 1-4 um inheight and ~13-22 um in width. In addition, superbeads(width of - 48-57 urn, beight of-2-3 nm) are occasionallyrevealed, two turns of DNA around the core particles arealso detected.
基金the National Natural Science Foundation of China, No. 30770758the Natural Science Research Program of Henan Provincial Department of Education, No. 2008A320032
文摘Bone marrow mesenchymal stem cells (MSCs) from rats were transfected with Rn-siRNA-caveolin-1 and differentiated into neuron-like cells using fasudil hydrochloride. Membrane ultrastructural changes in MSCs were observed under atomic force microscopy. Caveolin-l-transfected rat MSCs exhibited weak nuclear refraction, dense caveolae and long finger-like cellular processes prior to fasudil hydrochloride treatment. MSCs differentiating into neuron-like cells exhibited weak nuclear refraction and large cellular processes without caveolae. We hypothesize that caveolin-1 plays an important role in the regulation of bone marrow MSC differentiating into neuron-like cells.
基金Funded by the National Natural Science Foundation of China(Nos.51408287,and 51668038)the Rolls Supported by Program for Changjiang Scholars and Innovative Research Team in University(IRT_15R29)+2 种基金the Distinguished Young Scholars Fund of Gansu Province(1606RJDA318)the Natural Science Foundation of Gansu Province(1506RJZA064)the Excellent Program of Lanzhou Jiaotong University(201606)
文摘We investigated microstructure morphologies of three asphalts(SK, Karamay, and Esso) used in China using atomic force microscopy(AFM). The topography and phase contrast images were obtained. Topographic profile and three dimensional images were described. Roughnesses of microstructure were calculated. And the chemical compositions of asphalt were tested to explain the microstructural mechanism of the asphalt. The results show that the topography and phase image in atomic force microscopy are appropriate to evaluate the microstructure of the asphalt binder. There are significant differences in microstructural morphologies including bee-like structure, topographic profile, 3D image, and roughness for three asphalts in this study. There are three different phases in microstructure of asphalt binder. The oil source and chemical composition of asphalt, especially asphaltenes content have a great influence on the microstructure.
基金Supported by the National Natural Science Foundation of China,No. 30171036
文摘AIM: To find suitable solutions having lesser granules and keeping erythrocytes in normal shapes under atomic force microscopy (AFM). METHODS: Eight kinds of solutions, 1% formaldehyde, PBS buffer (pH7.2), citrate buffer (pH6.0), 0.9% NaCl, 5% dextrose, TAE, 1640 medium and 5% EDTA-K2, were selected from commonly used laboratory solutions, and venous blood from a healthy human volunteer was drawn and anticoagulated with EDTA-K2. Before scanned by AFM (NanoScopeIIIa SPM, Digital Instruments, Santa Barbara, CA), a kind of intermixture was deposited on freshly cleaved mica and then dried in the constant temperature cabinet (37 ℃). RESULTS: One percent formaldehyde, citrate buffer, 5% dextrose, TAE, were found to keep human erythrocytes in normal shape with few particles. Processed by these solutions, fine structures of human erythrocyte membrane were obtained. CONCLUSION: One percent formaldehyde, citrate buffer, 5% dextrose and TAE may be applied to dispose erythrocytes in AFM. The results may offer meaningful data for clinical diagnosis of blood by AFM.