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At least 1,387 records · Page 77Linked to original sources
PubMed1993

A COOH-terminal peptide confers regiospecific orientation and facilitates atomic force microscopy of an IgG1.

An antibody (IgG1) was designed for oriented adherence to a metal-containing surface. This was achieved by adding a metal-chelating peptide, (CP = His-Trp-His-His-His-Pro), to the COOH-terminus of the heavy chain through genetic engineering. Electroporation of the engineered heavy chain gene into cells expressing the complimentary light chain yielded colonies secreting an intact antibody containing the metal-chelating peptide (IgG1-CP) which had high affinity for a nickel-loaded iminodiacetate column. Purified IgG1-CP was bound to nickel-treated mica and imaged by atomic force microscopy (AFM). Antibody lacking the COOH-terminal metal binding peptide failed to produce discernible AFM images. The AFM images of individual IgG1-CP molecules and their calculated dimensions demonstrated that regiospecific binding and uniform orientation of the antibody was imparted by the peptide. The ability to stably orient macromolecules in their native state to a surface may be used advantageously to visualize them.

Amino Acid Sequence↗
PubMed2000

Drug-induced changes of cytoskeletal structure and mechanics in fibroblasts: an atomic force microscopy study.

The effect of various drugs affecting the integrity of different components of the cytoskeleton on the elasticity of two fibroblast cell lines was investigated by elasticity measurements with an atomic force microscope (AFM). Disaggregation of actin filaments always resulted in a distinct decrease in the cell's average elastic modulus indicating the crucial importance of the actin network for the mechanical stability of living cells. Disruption or chemical stabilization of microtubules did not affect cell elasticity. For the f-actin-disrupting drugs different mechanisms of drug action were observed. Cytochalasins B and D and Latrunculin A disassembled stress fibers. For Cytochalasin D this was accompanied by an aggregation of actin within the cytosol. Jasplakinolide disaggregated actin filaments but did not disassemble stress fibers. Fibrous structures found in AFM images and elasticity maps of fibroblasts could be identified as stress fibers by correlation of AFM data and fluorescence images.

3T3 Cells↗
PubMed2006

Electro-nanopatterning of surface relief gratings on azobenzene layer-by-layer ultrathin films by current-sensing atomic force microscopy.

The electro-nanopatterning and mechanism of pattern formation in azobenzene-containing layer-by-layer (LbL) ultrathin films is described using surface probe microscopy techniques. First, arrays of nanodots were patterned on these films to investigate applied time at constant voltage bias dependence in electro-nanopatterning. The anisotropic mass transport and polar alignment of the azobenzene-containing films were observed after applying the electric field and heating the sample locally with the cantilever tip. On the basis of this novel phenomenon, small-sized surface relief gratings (SRG)s and their alignment were fabricated and observed by current-sensing atomic force microscopy. The rate of mass transport for the polymer is mainly controlled by the applied time at constant voltage bias between the cantilever and the electrode/substrate.

Letter↗
PubMed2005

Novel methods for the production of silver microelectrode-arrays: their characterisation by atomic force microscopy and application to the electro-reduction of halothane.

A new method is proposed for the simple preparation of random silver micro and nano-electrode arrays. This employs acoustic streaming directed at a glassy carbon surface to "mechanically" attach particles from a suspension of metal colloidal or other small particles. The particles tend to adhere to the substrate at points of imperfection such as scratches, crevices etc. These arrays are compared with arrays formed by the electro-deposition of silver at a glassy carbon substrate, with the silver being partially stripped off, leaving a stable micro and nanoparticle array on the surface. Both surfaces are characterised using optical and atomic force microscopy. The two types of electrodes are evaluated to their analytical utility via the electrochemical reduction of halothane and their performance compared with that of a silver macroelectrode. A notable increase in sensitivity and peak current is observed.

Journal Article↗
PubMed1998

Mechanical properties of L929 cells measured by atomic force microscopy: effects of anticytoskeletal drugs and membrane crosslinking.

To shed light on the architecture of the cytoskeleton, we used the atomic force microscope (AFM) to measure the elasticity, viscoelasticity, and plasticity of L929 cells. The initial elastic response (Young's modulus approximately 4,000 Pa) of the cells to an applied force was followed by a slow compression of the cytoskeleton (tau 1/2 approximately equal to 10 s). When force application was terminated, the cytoskeleton underwent a sudden partial decompression and a subsequent slow, incomplete recovery. The role of the cytoskeletal elements in cell mechanics was accessed in AFM measurements carried out on cells treated with cytochalasin D, nocodazole, or colcemid. Cytochalasin D treatment reduced both elasticity (approximately 45%) and cytoplasmic viscosity (approximately 65%), whereas cells treated with nocodazole or colcemid exhibited a marked increase in elasticity (approximately 100%) and a slight increase in viscosity (approximately 15%). The AFM force measurements also provided evidence that the cell membrane and the cytoskeleton are mechanically coupled. Tightly adherent cells were stiffer than cells that were loosely attached. Moreover, cells crosslinked with either glutaraldehyde, 3, 3'-dithiobis [sulfosuccinimidylpropionate] (DTSSP), or Concanavalin A were more rigid than untreated cells. It is of interest that cells crosslinked with Concanavalin A, but not DTSSP, displayed plastic behaviors that may reflect the induction of cytoskeletal reorganization by Concanavalin A.

Actins↗
PubMed2002

Atomic force microscopy of height fluctuations of fibroblast cells.

We investigated the nanometer scale height fluctuations of 3T3 fibroblast cells with the atomic force microscope under physiological conditions. A correlation between these fluctuations and lateral cellular motility can be observed. Fluctuations measured on leading edges appear to be predominantly related to actin polymerization-depolymerization processes. We found fast (5 Hz) pulsatory behavior with 1-2 nm amplitude on a cell with low motility showing emphasized structure of stress fibers. Myosin driven contractions of stress fibers are thought to induce this pulsation.

3T3 Cells↗
PubMed2004

A convenient and rapid sample repositioning approach for atomic force microscopy.

A novel repositioning approach is described for repeated observations of a specimen at a close proximal location in the atomic force microscope. The approach is similar to keystone architecture, whereby the repositioning is achieved by forming a male structured base for the specimen, and a corresponding female counterpart as the frame. For the combination of an acrylic acid frame and a metal base, 90% translation shifts are less than 10 microm, and almost all angular disorientations are within +3 degrees to -3 degrees . Nanometre-scale surface features can be relocated easily and reliably even after 40 imaging-removal-imaging cycles, dipping the specimen in solutions or heating up to 500 degrees C.

Microscopy, Atomic Force↗
PubMed1995

The application of atomic force microscopy for the detection of microcrystals in synovial fluid from patients with recurrent synovitis.

Synovial fluid from 33 patients with inflammatory arthritis was examined with a polarized light microscope (PLM) and an atomic force microscope (AFM). Two samples were imaged with a transmission electron microscope (TEM) to determine calcium/phosphate ratios and identify microcrystals of calcium pyrophosphate dihydrate and octacalcium phosphate. Additional correlative x-ray diffraction studies were performed on several samples including purified hydroxyapatite and sodium chloride crystals. Monosodium urate, calcium pyrophosphate dihydrate, hydroxyapatite, octacalcium phosphate, and cholesterol crystals were identified with AFM. AFM images of these microcrystals revealed detailed surface topology, including lattice parameters and structural irregularities at the crystals' surface. These features were consistent with those obtained by TEM and x-ray diffraction studies. In addition, AFM images revealed that some specimens contained microcrystals that were undetected by PLM and/or TEM. These results suggest that AFM may provide a simple yet powerful technique for the detection of microcrystals in synovial fluid taken from patients with crystal-induced arthritis.

Arthritis↗
PubMed1999

[Observation of human corneal and scleral collagen fibrils by atomic force microscopy].

PURPOSE: We attempted to analyze the three-dimensional ultrastructure of human corneal and scleral collagen fibrils with an atomic force microscope (AFM). METHODS: A normal eye removed from a 66-year-old male was used in the study. Suspended corneal and scleral collagen fibrils were individually attached to glass slides by centrifugation. These collagen fibrils were air-dried and observed with a non-contact mode AFM in air. RESULTS: AFM imaging provided information on the surface topography of both corneal and scleral collagen fibrils. The corneal collagen fibrils had a height of 11.9 +/- 1.0 (mean +/- standard deviation) nm and the scleral fibrils of 82.5 +/- 35.6 nm. A periodic banding pattern of grooves and ridges was clearly found in both types of fibrils; the D-periodicity and the groove depth were 65.7 +/- 0.8 nm and 1.46 +/- 0.50 nm in the corneal fibrils, and 67.3 +/- 1.1 nm and 6.16 +/- 1.23 nm in the scleral fibrils. CONCLUSIONS: Surface topographic images of human corneal and scleral collagen fibrils were clearly obtained with the AFM. This technique provides quantitative information on the surface morphology of the collagen fibrils at high resolution.

Aged↗
PubMedDate not supplied

Observation of human corneal and scleral collagen fibrils by atomic force microscopy.

PURPOSE: We attempted to analyze the three-dimensional ultrastructure of human corneal and scleral collagen fibrils with an atomic force microscope (AFM). METHODS: A normal eye removed from a 66-year-old male patient during therapy was used in this study. Suspended corneal and scleral collagen fibrils were individually attached to glass slides by centrifugation. These collagen fibrils were air-dried and observed with a noncontact-mode AFM in air. RESULTS: AFM imaging provided information on the surface topography of both corneal and scleral collagen fibrils. The corneal collagen fibrils had a height of 11.9 +/- 1.0 nm (mean +/- SD) and scleral fibrils a height of 82.5 +/- 35.6 nm. A periodic banding pattern of grooves and ridges was clearly found on both types of fibrils; the D-periodicity and the groove depth were 65.7 +/- 0.8 nm and 1.46 +/- 0.50 nm in the corneal fibrils, and 67.3 +/- 1.1 nm and 6.16 +/- 1.23 nm in the scleral fibrils. CONCLUSIONS: Surface topographic images of human corneal and scleral collagen fibrils were clearly obtained with the AFM. This technique provides quantitative information on the surface morphology of the collagen fibrils at high resolution.

Aged↗
PubMed2004

Nanomanipulation of extended single-DNA molecules on modified mica surfaces using the atomic force microscopy.

The technique of nanometer scale manipulation is very important in constructing nano-structures and nano-devices. By using atomic force microscope, three kinds of controllable manipulation on single-DNA molecules were introduced in the paper. DNA molecules deposited and extended on modified mica surface were first imaged by tapping mode, then cutting, bending, and pushing were respectively performed on single-DNA molecules. The results of the manipulation depend on the interaction between tip and DNA as well as between substrate and DNA.

Aluminum Silicates↗
PubMed1995

Atomic force microscopy of the cornea and sclera.

We report the first investigation of the extracellular matrix of cornea and sclera using an atomic force microscope (AFM), and evaluate the potential of this new technique. We were able to obtain 2-3 nanometre resolution of both tissues in a condition close to their native state. The AFM was able to resolve surface features on the collagen fibrils, as well as providing unique images of crossbridge structures between collagen fibrils in both cornea and sclera.

Animals↗
PubMed1998

Voltage-dependent membrane displacements measured by atomic force microscopy.

Cells use polar molecules in the membrane to sense changes in the transmembrane potential. The opening of voltage-gated ion channels and membrane bending due to the inverse flexoelectric effect are two examples of such electromechanical coupling. We have looked for membrane motions in an electric field using atomic (or scanning) force microscopy (AFM) with the intent of studying voltage-dependent conformational changes of ion channels. Voltage-clamped HEK293 cells were either untransfected controls or transfected with Shaker K+ channels. Using a +/- 10-mV peak-peak AC carrier stimulus, untransfected cells moved 0.5-15 nm normal to the plane of the membrane. These movements tracked the voltage at frequencies >1 kHz with a phase lead of 60-120 degrees, as expected of a displacement current. The movement was outward with depolarization, but the holding potential only weakly influenced the amplitude of the movement. In contrast, cells transfected with a noninactivating mutant of Shaker K+channels showed similar movements, but these were sensitive to the holding potential; decreasing with depolarization between -80 and 0 mV. Searching for artifactual origins of these movements, we used open or sealed pipettes and AFM cantilever placements just above the cells. These results were negative, suggesting that the observed movements were produced by the cell membrane rather than by movement of the patch pipette, or by acoustic or electrical interactions of the membrane with the AFM tip. In control cells, the electrical motor may arise from the flexoelectric effect, where changes in potential induce changes in curvature. In transfected cells, it appears that channel-specific movements also occurred. These experiments demonstrate that the AFM may be able to exploit voltage-dependent movements as a source of contrast for imaging membrane components. The electrically induced motility will cause twitching during action potentials, and may have physiological consequences.

Artifacts↗
PubMedDate not supplied

Ultrastructural investigation of human sperm using atomic force microscopy.

Ultrastructural investigation of human sperm in its natural environment (without fixation, dehydration, embedding, sectioning, etc.) was carried out by using atomic force microscope (AFM) in its tapping mode. This technique permits the examination of fine structural details of undamaged sperm and its topography with precision. Moreover, it allows 3D reconstruction of images and enhances the contrast to resolve details such as mitochondria that surround the axoneme at the sperm middle piece. An organized structure has been found in the flageller axoneme region. Ultrastructure also reveals folding and details of the depression of the membrane that cannot be examined with conventional techniques.

Humans↗
PubMed2000

Characterization by atomic force microscopy of fused-silica capillaries chemically modified for capillary electrokinetic chromatography

Fused-silica capillary tubes with 50-microm bores have been chemically modified to yield octadecyl-derivatized surfaces with increased surface area. Alkylation is achieved in three steps: etching, silane adlayering, and olefin hydrosilation. Surface roughness, surface area, surface-tip attractive forces, and topographic images of the native, etched, silane-adlayered, and alkylated capillary bores as measured by atomic force microscopy are presented here. Significant roughening occurs during the etching process, but the most dramatic change in roughness and surface adhesion forces occurs in the hydrided (silane-adlayered) capillary surface. Topographic smoothing and passivation of surface activity are observed for the alkylated capillary surface.

Journal Article↗
PubMed2006

Probing membrane proteins using atomic force microscopy.

To gain insights into how biological molecules function, advanced technologies enabling imaging, sensing, and actuating single molecules are required. The atomic force microscope (AFM) would be one of novel potential tools for these tasks. In this study, techniques and efforts using AFM to probe biomolecules are introduced and reviewed. The state-of-art techniques for characterizing specific single receptor using the functionalized AFM tip are discussed. An example of studying the angiotensin II type 1 (AT1) receptors expressed in sensory neuronal cells by AFM with a functionalized tip is given. Perspectives for identifying and characterizing specific individual membrane proteins using AFM in living cells are provided. Given that many diseases have their roots at the molecular scale and are best understood as a malfunctioning biological nanomachines, the prospects of these unique techniques in basic biomedical research or in clinical practice are beyond our imagination.

Animals↗
PubMed1995

Atomic force microscopy of conditioning agents on dentin.

Dentin conditioners provide a microporous surface for penetration by bonding agents. This study used an atomic force microscope (AFM) to examine the initial steps in the conditioning process of dentin using three demineralizing agents, 0.5 M EDTA, and dilute solutions of phosphoric (3 mM, 6 mM) and citric (5 mM) acids, in order to establish the relationships between demineralization and changes in surface morphology. Polished dentin disks had a 10-nm-thick gold pattern applied which served as a height reference. Samples (n = 3/agent) were examined at baseline and at 2-s intervals for up to 120 s for each agent. EDTA (0.5 M) was used as received; other conditioners were diluted to slow the rats of demineralization for detailed study. The surfaces of the peritubular and intertubular regions were altered differently. Initially subsidence rates were equal and linear, but after a 100-nm depth change the intertubular rates decreased. For phosphoric acid and citric acid, the movement of the intertubular surface was uniform and the surfaces remained smooth. However, the intertubular surfaces were rough for the EDTA treatment. The surface subsidence reached a plateau after a depth change of about 0.5 microns, which resulted from a limit to the contraction of the demineralized and hydrated collagen scaffold.

Chelating Agents↗
PubMed2006

Looking at the micro-topography of polished and blasted Ti-based biomaterials using atomic force microscopy and contact angle goniometry.

Surface topography of polished and blasted samples of a Ti6Al4V biomaterial has been studied using an atomic force microscope. Surface RMS roughness and surface area have been measured at different scales, from 1 to 50 microm, while at distances below 10 microm the surface RMS roughness in both kinds of samples is not very different, this difference becomes significant at larger scanning sizes. This means that the surface roughness scale that could have a main role in cell adhesion varies depending on the size, shape and flexibility of participating cells. This consideration suggests that in cell-material interaction studies, surface roughness should not be considered as an absolute and independent property of the material, but should be measured at scales in the order of the cell sizes, at least if a microscopic interpretation of the influence of roughness on the adhesion is intended. The microscopic information is contrasted with that coming from a macroscopic approach obtained by contact angle measurements for polar and non-polar liquids whose surface tension is comprised in a broad range. Despite the very large differences of contact angles among liquids for each surface condition, a similar increase for the blasted surface with respect to the polished has been found. Interpretation of these results are in accordance with the microscopic analysis done through the use of a functional roughness parameter, namely the valley fluid retention index, evaluated from the AFM images, which has been shown not to correlate with the RMS roughness, one of the most commonly used roughness parameter.

Alloys↗