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1.
Salavat?R. Nabiev Denis?A. Ovsyannikov Galina?V. Kopylova Daniil?V. Shchepkin Alexander?M. Matyushenko Natalia?A. Koubassova Dmitrii?I. Levitsky Andrey?K. Tsaturyan Sergey?Y. Bershitsky 《Biophysical journal》2015,109(2):373-379
A two-beam optical trap was used to measure the bending stiffness of F-actin and reconstructed thin filaments. A dumbbell was formed by a filament segment attached to two beads that were held in the two optical traps. One trap was static and held a bead used as a force transducer, whereas an acoustooptical deflector moved the beam holding the second bead, causing stretch of the dumbbell. The distance between the beads was measured using image analysis of micrographs. An exact solution to the problem of bending of an elastic filament attached to two beads and subjected to a stretch was used for data analysis. Substitution of noncanonical residues in the central part of tropomyosin with canonical ones, G126R and D137L, and especially their combination, caused an increase in the bending stiffness of the thin filaments. The data confirm that the effect of these mutations on the regulation of actin-myosin interactions may be caused by an increase in tropomyosin stiffness. 相似文献
2.
Mechanical and structural properties underlying contraction of skeletal muscle fibers after partial 1-ethyl-3-[3-dimethylamino)propyl]carbodiimide cross-linking. 总被引:1,自引:0,他引:1 下载免费PDF全文
S Bershitsky A Tsaturyan O Bershitskaya G Mashanov P Brown M Webb M A Ferenczi 《Biophysical journal》1996,71(3):1462-1474
We show prolonged contraction of permeabilized muscle fibers of the frog during which structural order, as judged from low-angle x-ray diffraction, was preserved by means of partial cross-linking of the fibers using the zero-length cross-linker 1-ethyl-3-[3-dimethylamino)propyl]carbodiimide. Ten to twenty percent of the myosin cross-bridges were cross-linked, allowing the remaining 80-90% to cycle and generate force. These fibers displayed a well-preserved sarcomeric order and mechanical characteristics similar to those of intact muscle fibers. The intensity of the brightest meridional reflection at 14.5 nm, resulting from the projection of cross-bridges evenly spaced along the myofilament length, decreased by 60% as a relaxed fiber was deprived of ATP and entered the rigor state. Upon activation of a rigorized fiber by the addition of ATP, the intensity of this reflection returned to 97% of the relaxed value, suggesting that the overall orientation of cross-bridges in the active muscle was more perpendicular to the filament axis than in rigor. Following a small-amplitude length step applied to the active fibers, the reflection intensity decreased for both releases and stretches. In rigor, however, a small stretch increased the amplitude of the reflection by 35%. These findings show the close link between cross-bridge orientation and tension changes. 相似文献
3.
A direct modeling approach was used to quantitatively interpret the two-dimensional x-ray diffraction patterns obtained from contracting mammalian skeletal muscle. The dependence of the calculated layer line intensities on the number of myosin heads bound to the thin filaments, on the conformation of these heads and on their mode of attachment to actin, was studied systematically. Results of modeling are compared to experimental data collected from permeabilized fibers from rabbit skeletal muscle contracting at 5°C and 30°C and developing low and high isometric tension, respectively. The results of the modeling show that: i), the intensity of the first actin layer line is independent of the tilt of the light chain domains of myosin heads and can be used as a measure of the fraction of myosin heads stereospecifically attached to actin; ii), during isometric contraction at near physiological temperature, the fraction of these heads is ∼40% and the light chain domains of the majority of them are more perpendicular to the filament axis than in rigor; and iii), at low temperature, when isometric tension is low, a majority of the attached myosin heads are bound to actin nonstereospecifically whereas at high temperature and tension they are bound stereospecifically. 相似文献
4.
Tsaturyan AK Koubassova N Ferenczi MA Narayanan T Roessle M Bershitsky SY 《Biophysical journal》2005,88(3):1902-1910
Calculation of the size of the power stroke of the myosin motor in contracting muscle requires knowledge of the compliance of the myofilaments. Current estimates of actin compliance vary significantly introducing uncertainty in the mechanical parameters of the motor. Using x-ray diffraction on small bundles of permeabilized fibers from rabbit muscle we show that strong binding of myosin heads changes directly the actin helix. The spacing of the 2.73-nm meridional x-ray reflection increased by 0.22% when relaxed fibers were put into low-tension rigor (<10 kN/m(2)) demonstrating that strongly bound myosin heads elongate the actin filaments even in the absence of external tension. The pitch of the 5.9-nm actin layer line increased by approximately 0.62% and that of the 5.1-nm layer line decreased by approximately 0.26%, suggesting that the elongation is accompanied by a decrease in its helical angle (approximately 166 degrees) by approximately 0.8 degrees. This effect explains the difference between actin compliance revealed from mechanical experiments with single fibers and from x-ray diffraction on whole muscles. Our measurement of actin compliance obtained by applying tension to fibers in rigor is consistent with the results of mechanical measurements. 相似文献
5.
Biophysics - The temperature dependences of the tension and stiffness of actively contracting single fibers of the rabbit slow muscle (m. soleus) were studied using the Joule temperature jump.... 相似文献
6.
A mathematical model of the propagation of acoustic shear waves in muscle tissue is considered. Muscle is modeled as an incompressible
transversely isotropic viscoelastic continuum with quasi-one-dimensional active tension. There are two types of shear waves
in an infinite medium. Waves of the second type (transverse) propagate without decay even when myofibril viscosity is taken
into account. A problem of standing transverse waves in a rectangular layer was investigated numerically. The values of the
problem parameters are found for which one can easily estimate the active tension (or muscle tone) from the characteristics
of standing waves. This value is informative for diagnostics of the muscle state. 相似文献
7.
A structural and kinetic model of actomyosin interaction in a contracting muscle fiber has been proposed, based on the assumption that the myosin molecular motor generates force in two steps. Initially, a nonstereospecifically attached myosin head rolls on the actin surface and stereospecifically locks on actin. Then its α-helical lever arm (neck domain) tilts about its catalytic domain. The model also includes the modern scheme of ATP hydrolysis by actomyosin. The results of modeling presented here quantitatively reproduce all experimentally observed characteristics of the responses of tension and stiffness of muscle fibers to T-jumps of different amplitudes. 相似文献
8.
I. O. Petrova S. A. Tyganov T. M. Mirzoev A. K. Tsaturyan I. B. Kozlovskaya B. S. Shenkman 《Doklady. Biochemistry and biophysics》2018,481(1):205-207
The study was aimed at testing the hypotheses about the role of cross-bridges and calpains in reduction of rat soleus passive tension under conditions of hindlimb unloading. For this purpose, we used an inhibitor of μ-calpain PD 150606 as well as a blocker of actomyosin interaction (blebbistatin). It was found for the first time that a decrease in passive tension of rat soleus after 3-day hindlimb unloading is associated with the activity of μ-calpain and does not depend on the processes of cross-bridges formation. 相似文献
9.
We present a model of Ca-regulated thin filaments in cardiac muscle where tropomyosin is treated as a continuous elastic chain confined in the closed position on the actin helix by electrostatic forces. The main distinction from previous works is that the intrinsic stress-free helical shape of the tropomyosin chain was taken into account explicitly. This results in the appearance of a new, to our knowledge, tension-like term in the energy functional and the equilibrium equation. The competitive binding of calcium and the mobile segment of troponin-I to troponin-C were described by a simple kinetic scheme. The values of dimensionless model parameters were estimated from published data. A stochastic Monte Carlo simulation of calcium curves has been performed and its results were compared to published data. The model explains the high cooperativity of calcium response of the regulated thin filaments even in the absence of myosin heads. The binding of myosin heads to actin increases the calcium sensitivity while not affecting its cooperativity significantly. When the presence of calcium-insensitive troponin-C was simulated in the model, both calcium sensitivity and cooperativity decreased. All these features were previously observed experimentally. 相似文献
10.
The interaction of actin and myosin powers striated and smooth muscles and some other types of cell motility. Due to its highly
ordered structure, skeletal muscle is a very convenient object for studying the general mechanism of the actin-myosin molecular
motor. The history of investigation of the actin-myosin motor is briefly described. Modern concepts and data obtained with
different techniques including protein crystallography, electron microscopy, biochemistry, and protein engineering are reviewed.
Particular attention is given to X-ray diffraction studies of intact muscles and single muscle fibers with permeabilized membrane
as they give insight into structural changes that underlie force generation and work production by the motor. Time-resolved
low-angle X-ray diffraction on contracting muscle fibers using modern synchrotron radiation sources is used to follow movement
of myosin heads with unique time and spatial resolution under near physiological conditions. 相似文献