High-resolution e-beam patterning exposure of the surface of poly[(tert-butyl-methacrylate)-co-(methyl methacrylate)]-a common e-beam and deep-UV resist used in semiconductor microlithography-induced sharp changes in the surface hydrophobicity. These differences in hydrophobicity resulted in the selective attachment of heavy meromyosin to hydrophobic, unexposed surfaces. The movement of the actin filaments on myosin-rich and ...

Kinesin and nonclaret disjunctional protein (ncd) are two microtubule-based molecular motors that use energy from ATP hydrolysis to drive motion in opposite directions. They are structurally very similar and bind with similar orientations on microtubule. What is the origin of the different directionality? Is it some subtle feature of the ...

We have used time-resolved phosphorescence anisotropy (TPA) to study the rotational dynamics of chicken gizzard regulatory light chain (RLC) bound to scallop adductor muscle myofibrils in key physiological states. Native RLC from scallop myofibrils was extracted and replaced completely with gizzard RLC labeled specifically at Cys 108 with erythrosin iodoacetamide ...

Kinesin is a two-headed, ATP-driven motor protein that moves processively along microtubules in discrete steps of 8 nm, probably by advancing each of its heads alternately in sequence. Molecular details of how the chemical energy stored in ATP is coupled to mechanical displacement remain obscure. To shed light on this ...

We have performed a real time analysis of fluorescence-tagged vesicle and mitochondria movement in living CHO cells transfected with microtubule-associated protein tau or its microtubule-binding domain. tau does not alter the speed of moving vesicles, but it affects the frequencies of attachment and detachment to the microtubule tracks. Thus, tau ...

We have visualized bundles of the actin filaments of a Characean internodal cell and investigated the sliding motion of organelles with myosin on the bundles. The investigation revealed that a power spectrum of the sliding velocity time series of the organelle has two remarkable peaks near 4 and 7.5 Hz. ...

The position of the myosin head with respect to the filament backbone is thought to be a function of pH, ionic strength (micro) and the extent of regulatory light chain (RLC) phosphorylation [Harrington (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 5066-5070]. The object of this study is to examine the ...

In order to understand the molecular mechanism of relaxation phenomena in collagenous tissue, time-resolved, small-angle X-ray diffraction measurements were performed on bovine Achilles tendon collagen under creep. A tension-induced increase in the 67 nm period (D-period) was observed, and the strain in the D-period, epsilon D, was found to be ...

The mechanical manipulation of single biological molecules is stimulating new and exciting research in many fields of study, including molecular motor mechanics, biopolymer properties, protein unfolding, receptor-ligand interactions, and more. Some recent highlights include the elucidation of the coupling ratios of myosin and kinesin, the demonstration of oscillatory forces in ...

Actomyosin, a complex of actin filaments and myosin motor proteins, is responsible for force generation during muscle contraction. To resolve the individual mechanical events of force generation by actomyosin, we have developed a new instrument with which we can capture and directly manipulate individual myosin subfragment-1 molecules using a scanning ...

The speed of the myofilament lattice spacing response to rapid changes in load or length of single, intact muscle fibres of the frog, was investigated during isometric tetani. During ramp releases at close to Vmax and during step length changes (completed within 250 microseconds), lattice spacing was calculated from the ...

Lizards commonly move on steep inclines in nature, but no previous studies have investigated whether the kinematics of the limbs of lizards differ on inclined surfaces compared with level surfaces. Therefore, we examined how the kinematics of the hindlimb were affected by both incline (downhill 30 degrees, level and uphill ...

The technique of electrorotation was used to apply torque to cells of the bacterium Escherichia coli tethered to glass coverslips by single flagella. Cells were made to rotate backward, that is, in the direction opposite to the rotation driven by the flagellar motor itself. The torque generated by the motor ...

Statocytes from plant root caps are characterized by a polar arrangement of cell organelles and sedimented statoliths. Cortical microtubules and actin microfilaments contribute to development and maintenance of this polarity, whereas the lack of endoplasmic microtubules and prominent bundles of actin microfilaments probably facilitates sedimentation of statoliths. High-resolution video microscopy ...

In muscle, work is performed by myosin cross-bridges during interactions with actin filaments. The amount of work performed during each interaction can be related to the mechanical properties of the cross-bridge; work is the integral of the force produced with respect to the distance that the cross-bridge moves the actin ...

Measurements of movement along 28 boreholes reveal the three-dimensional flow field in a 6 million cubic meter reach of Worthington Glacier, a temperate valley glacier located in Alaska. Sliding at the bed accounted for 60 to 70 percent of the glacier's surface motion. Strain rates in the ice were low ...

Eukaryotic flagella beat rhythmically. Dynein is a protein that powers flagellar motion, and oscillation may be inherent to this protein. Here we determine whether oscillation is a property of dynein arms themselves or whether oscillation requires an intact axoneme, which is the central core of the flagellum and consists of ...

To provide information on the mechanism of cardiac adaptation at the molecular level, we compared the unitary displacements and forces between the 2 rat cardiac myosin isoforms, V1 and V3. A fluorescently labeled actin filament, with a polystyrene bead attached, was caught by an optical trap and brought close to ...

Although previous laboratory studies have commonly determined sprinting speeds of lizards on horizontal surfaces, the speeds and slopes used during the escapes of lizards in natural habitats with variable inclines are virtually unstudied. To quantify performance and the use of inclined surfaces during escape, we took advantage of the footprints ...

We present an analysis of the planar motion of single semiflexible filaments subject to viscous drag or point forcing. These are the relevant forces in dynamic experiments designed to measure biopolymer bending moduli. By analogy with the "Stokes problems" in hydrodynamics (motion of a viscous fluid induced by that of ...

Gravitropic bending of Lepidium roots caused by intermittent stimulation lasting approximately 1 h was the same for a particular sum of stimulation intervals and was independent of (i) the length of a single stimulation interval (from 1 to 12.2 s) during which the roots were exposed unilaterally and horizontally, and ...

The fluctuation in the sliding distance of cytoskeletal filaments driven to move by protein motors in vitro does not depend on the filament length. This is in sharp contrast to the case of Brownian movement of filamentous particles in their longitudinal directions, in which the positional fluctuation is proportional to ...

Muscle contraction is generally thought to involve tilting of the light chain region of the myosin head. This could account for 5-10 nm of axial displacement as it moves from nearly perpendicular to the filament axis (the state at the beginning of the working stroke) to the rigor conformation (at ...

A long-range repulsive force near isolated neurofilaments was detected by exclusion of large molecules and by direct force measurements with atomic force microscopy. Adsorption of isolated native neurofilaments to a solid substrate in a high-salt solution (170 mM NaCl), in the presence of coisolating contaminants, shows that the contaminants are ...

Three mutant strains of Dictyostelium discoideum, lacking different actin-binding proteins, were tested for behavioural deficits in the multicellular pseudoplasmodium (slug) stage. Two strains, defective in the production of either -actinin (an actin cross-linker) or severin (an actin capping and severing protein), did not show changes in slug behaviour. Slugs of ...

We tested the hypothesis that the Frank-Starling relationship is mediated by changes in the rate of cross-bridge detachment in cardiac muscle. We simultaneously measured isometric force development and the rate of ATP consumption at various levels of Ca2+ activation in skinned rat cardiac trabecular muscles at three sarcomere lengths (2.0, ...

Forces generated by protein polymerization are important for various forms of cellular motility. Assembling microtubules, for instance, are believed to exert pushing forces on chromosomes during mitosis. The force that a single microtubule can generate was measured by attaching microtubules to a substrate at one end and causing them to ...

Motor activity is a good index for studying the effects of pharmacological agents. Previous investigations have measured spontaneous motor activity by counting the number of times that an animal interrupts a magnetic field or photocell beam. Quite recently, a novel activity-monitoring system, Supermex, was developed. In this system, a sensor ...

In the crab Hemigrapsus sanguineus, maintained under a 12 h:12 h light:dark cycle, the amount of vesicular smooth endoplasmic reticulum (vesicular sER) in the photoreceptor cell body increases after the light is turned off. This paper demonstrates that actin filaments in the photoreceptor cell body are involved in the transport ...

A key goal in the study of the function of ATP-driven motor enzymes is to quantify the movement produced from consumption of one ATP molecule. Discrete displacements of the processive motor kinesin along a microtubule have been reported as 5 and/or 8 nm. However, analysis of nanometre-scale movements is hindered ...

By examining the mechanical properties of isolated skeletal and cardiac myofibrils in calcium-free, ATP-containing solution, we attempted to separate the stiffness contribution of titin filaments from that of weakly bound cross bridges. Efforts to enhance weak cross-bridge binding by lowering ionic strength were met by clear contractile responses. Even at ...

To relate transients of force by single kinesin molecules with the elementary steps of the ATPase cycle, we measured the time to force generation by kinesin after photorelease of ATP from caged ATP. Kinesin-coated beads were trapped by an infrared laser and brought onto microtubules fixed to a coverslip. Tension ...

This article summarizes the author's presentation at the Baylor Medical School Symposium on the Biophysics of Microtubules, held April 12 to 14, 1996, in Houston, Texas. It presents a brief historical sketch and discusses the role that assembly/disassembly of microtubules is likely to be playing in force generation for chromosome ...

Stretch and release experiments carried out on skinned single fibers of frog skeletal muscle under rigor conditions indicate that the elastic properties of the fiber depend on strain. For modulation frequencies below 1000 Hz, the results show an increase in Young's modulus of 20% upon a stretch of 1 nm/half-sarcomere. ...

What is unique to biodynamics in vivo or dynamics leading to the emergence of biological organizations is a frozen aggregate of degrees of freedom in motion that can change its constituent members in time. Association and dissociation of degrees of freedom in the frozen aggregate is information-generative, in the sense ...

Differential thresholds for viscosity were measured in ten subjects with the use of an adaptive two-alternative forced-choice procedure. An electromagnetic linear motor was connected to each wrist and the viscosity of the motors was under computer servo control. For each block of 50 trials the viscosity of one motor was ...

1. The time course of cross-bridge detachment-attachment following a step stretch was determined in single frog muscle fibres (at 4 degrees (1 and 2.1 microns sarcomere length) by imposing, under sarcomere length control by a striation follower, test step releases of various amplitudes (2-13 nm per half-sarcomere) at successive times ...

Evidence for actin-dependent organelle movement was first obtained from studies of cytoplasmic streaming in plants. These studies, together with cell-free organelle motility studies and biophysical analyses of muscle myosin, support a model whereby organelle-associated motor molecules utilize the energy of adenosine triphosphate binding and hydrolysis to drive movement along F-actin ...

Descriptions are given of three kinds of symmetries encountered in studies of bacterial locomotion, and of the ways in which they are circumvented or broken. A bacterium swims at very low Reynolds number: it cannot propel itself using reciprocal motion (by moving through a sequence of shapes, first forward and ...

Knowledge of the elastic properties of actin filaments is crucial for considering its role in muscle contraction, cellular motile events, and formation of cell shape. The stiffness of actin filaments in the directions of stretching and bending has been determined. In this study, we have directly determined the torsional rigidity ...

An in situ field study of the motility patterns exhibited by Phormidium corallyticum and Beggiatoa spp. in black-band disease of corals was conducted over a 5-day period. Measurements were made at a spatial resolution of 50 &mgr;m to document the horizontal migration of black-band across living coral tissue, while vertical ...

In search for the cellular mechanisms of graviperception in basidiomycete fruit bodies, nuclear and vacuole motility was investigated in the fungus, Flammulina velutipes. In this organism, hyphal nuclei are closely linked with the actin cytoskeleton, which is involved in gravity perception. Active motion of the nuclei appears aligned with the ...

One- and two-dimensional high-spatial-frequency dielectric surface-relief gratings on a Au substrate are used to design a high-reflectance quarter-wave retarder at 70° angle of incidence and 10.6-μm light wavelength. The equivalent homogeneous anisotropic layer model is used. It is shown that equal and high reflectances (>98.5%) for the p and the ...

The effects of purified recombinant microtubule-associated protein 2c (rMAP2c) on the dynamic instability of microtubules were examined by direct observation of individual microtubules in vitro by video-enhanced differential interference contrast light microscopy. Microtubules were grown in the absence or presence of varying concentrations of rMAP2c and were analyzed to determine ...

To ensure optimal sensitivity for mechanoelectrical transduction, hair cells adapt to prolonged stimuli using active motors. Adaptation motors are thought to employ myosin molecules as their force-producing components. We find that beryllium fluoride, vanadate, and sulfate, phosphate analogs that inhibit the ATPase activity of myosin, inhibit adaptation by abolishing motor ...

Kinesin is a two-headed motor protein that powers organelle transport along microtubules. Many ATP molecules are hydrolysed by kinesin for each diffusional encounter with the microtubule. Here we report the development of a new assay in which the processive movement of individual fluorescently labelled kinesin molecules along a microtubule can ...

When neutrophil leukocytes are stimulated by chemotactic factors or by substratum contact, they change their shape. Shape changes are a prerequisite for cellular migration and typically involve the extrusion of thin, veil-like lamellipods and the development of morphological polarity. Stimulation also leads to changes in the neutrophil content of filamentous ...

We have correlated the mobility and the generation of force of myosin heads by applying radial compression to isometrically contracting muscle fibers. Osmotic pressure was produced by dextran T-500, and its effect on the orientation and mobility of myosin heads labeled with N-(1-oxy-2,2,5,5-tetramethyl-4-pyperidinyl)maleimide was observed by conventional and saturation-transfer electron ...

We measured forces generated by myosin molecules and a single actin filament using an optical trap system. The force per unit length of actin filament did not differ significantly between cardiac myosin isoforms. V1 and V3. This indicates that the ability to generate force is equal between V1 and V3, ...

We studied the fluctuation in the translational sliding movement of microtubules driven by kinesin in a motility assay in vitro. By calculating the mean-square displacement deviation from the average as a function of time, we obtained motional diffusion coefficients for microtubules and analyzed the dependence of the coefficients on microtubule ...