Ion channels in small cells and subcellular structures can be studied with a smart patch-clamp system.
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We have developed a scanning patch-clamp technique that facilitates single-channel recording from small cells and submicron cellular structures that are inaccessible by conventional methods. The scanning patch-clamp technique combines scanning ion conductance microscopy and patch-clamp recording through a single glass nanopipette probe. In this method the nanopipette is first scanned over a cell surface, using current feedback, to obtain a high-resolution topographic image. This same pipette is then used to make the patch-clamp recording. Because image information is obtained via the patch electrode it can be used to position the pipette onto a cell with nanometer precision. The utility of this technique is demonstrated by obtaining ion channel recordings from the top of epithelial microvilli and openings of cardiomyocyte T-tubules. Furthermore, for the first time we have demonstrated that it is possible to record ion channels from very small cells, such as sperm cells, under physiological conditions as well as record from cellular microstructures such as submicron neuronal processes. (+info)
Scanning probe microscopy for chromosomal research.
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The study of chromosome structure with scanning probe microscopy provides a range of information from three-dimensional topographic structures through mechanical properties to optical information, usually fluorescence. For atomic force microscopy studies, the importance of removing cell debris from the chromosome surface has been recognized. Studies in aqueous environments reveal a highy swollen and tough chromosomal structure, but the charge interaction between the probe and specimen needs to be considered if high-resolution images are to be achieved. This charge interaction can be used to extract DNA strands of about 2 kbp from the chromosome. SPM studies of chromosomes may also be of value in the identification of defective chromosomes with either duplications or deletions. (+info)
Extended, relaxed, and condensed conformations of hyaluronan observed by atomic force microscopy.
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The conformation of the polysaccharide hyaluronan (HA) has been investigated by tapping mode atomic force microscopy in air. HA deposited on a prehydrated mica surface favored an extended conformation, attributed to molecular combing and inhibition of subsequent chain recoil by adhesion to the structured water layer covering the surface. HA deposited on freshly cleaved mica served as a defect in a partially structured water layer, and favored relaxed, weakly helical, coiled conformations. Intramolecularly condensed forms of HA were also observed, ranging from pearl necklace forms to thick rods. The condensation is attributed to weak adhesion to the mica surface, counterion-mediated attractive electrostatic interactions between polyelectrolytes, and hydration effects. Intermolecular association of both extended and condensed forms of HA was observed to result in the formation of networks and twisted fibers, in which the chain direction is not necessarily parallel to the fiber direction. Whereas the relaxed coil and partially condensed conformations of HA are relevant to the native structure of liquid connective tissues, fully condensed rods may be more relevant for HA tethered to a cell surface or intracellular HA, and fibrous forms may be relevant for HA subjected to shear flow in tight intercellular spaces or in protein-HA complexes. (+info)
Study of the surface morphology of a cholesteryl tethering system for lipidic bilayers.
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The immobilization of functional molecules embedded in lipidic membranes onto inorganic substrates is of great interest for numerous applications in the fields of biosensors and biomaterials. We report on the preparation and the morphological characterization of a tethering system for lipidic bilayers, which is based on cholesteryl derivatives deposited on hydrophilic surfaces by self-assembling and microcontact printing techniques. The investigation of the structural properties of the realized films by atomic, lateral, and surface potential microscopy allowed us to assess the high quality of the realized cholesteryl layers. (+info)
Nanoscale imaging of buried structures via scanning near-field ultrasound holography.
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A nondestructive imaging method, scanning near-field ultrasound holography (SNFUH), has been developed that provides depth information as well as spatial resolution at the 10- to 100-nanometer scale. In SNFUH, the phase and amplitude of the scattered specimen ultrasound wave, reflected in perturbation to the surface acoustic standing wave, are mapped with a scanning probe microscopy platform to provide nanoscale-resolution images of the internal substructure of diverse materials. We have used SNFUH to image buried nanostructures, to perform subsurface metrology in microelectronic structures, and to image malaria parasites in red blood cells. (+info)
Elasticity and adhesion of resting and lipopolysaccharide-stimulated macrophages.
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Colloidal Force Microscopy was employed to study the viscoelastic and adhesive properties of macrophages upon stimulation with lipopolysaccharide (LPS). Force vs. distance measurements were performed. The adhesion of LPS-stimulated cells (separation force=37+/-3 nN) was almost twice as high as that of resting macrophages (16+/-1 nN). Upon retraction pulling of membrane tethers was observed. Tether lengths and forces at which rupture take place did not depend on stimulation. The reduced Young's modulus K, a measure of cytoskeleton elasticity, was three times lower than that of the control. The data show that LPS has profound effects on cytomechanical and adhesion properties of macrophages. (+info)
Metallic magnetic nanoparticles.
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In this paper, we reviewed some relevant aspects of the magnetic properties of metallic nanoparticles with small size (below 4 nm), covering the size effects in nanoparticles of magnetic materials, as well as the appearance of magnetism at the nanoscale in materials that are nonferromagnetic in bulk. These results are distributed along the text that has been organized around three important items: fundamental magnetic properties, different fabrication procedures, and characterization techniques. A general introduction and some experimental results recently obtained in Pd and Au nanoparticles have also been included. Finally, the more promising applications of magnetic nanoparticles in biomedicine are indicated. Special care was taken to complete the literature available on the subject. (+info)
Noncontact dielectric friction.
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Dielectric fluctuations are shown to be the dominant source of noncontact friction in high-sensitivity scanning probe microscopy of dielectric materials. Recent measurements have directly determined the friction acting on custom-fabricated single-crystal silicon cantilevers whose capacitively charged tips are located 3-200 nm above thin films of poly(methyl methacrylate), poly(vinyl acetate), and polystyrene. Differences in measured friction among these polymers are explained here by relating electric field fluctuations at the cantilever tip to dielectric relaxation of the polymer. (+info)