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31.
Sergey Y. Bershitsky Natalia A. Koubassova Michael A. Ferenczi Andrey K. Tsaturyan 《Biophysical journal》2010,99(6):1827-1834
Raising the temperature of rabbit skeletal muscle from ∼0°C to ∼20°C has been shown to enhance the helical organization of the myosin heads and to change the intensities of the 10 and 11 equatorial reflections. We show here by time-resolved x-ray diffraction combined with temperature jump that the movement of the heads to enhance the organized myosin helix occurs at the same fast rate as the change in the intensities of the equatorial reflections. However, model calculations indicate that the change in the equatorials cannot be explained simply in terms of the movement of myosin heads. Analysis of electron micrographs of transverse sections of relaxed muscle fibers cryofixed at ∼5°C and ∼35°C shows that in addition to the reorganization of the heads the thin and thick filaments are less constrained to their positions in the hexagonal filament lattice in the warm muscle than in the cold. Incorporating the changes in filament order in model calculations reconciles these with the observed changes in equatorial reflections. We suggest the thin filaments in the cold muscle are boxed into their positions by the thermal movement of the disordered myosin heads. In the warmer muscle, the packed-down heads leave the thin filaments more room to diffuse laterally. 相似文献
32.
A simple kinetic model of muscle contraction is suggested. The rates of cross-bridge transitions from one kinetic state to another one are supposed to depend on the strain averaged over an ensemble of actin-bound bridges. With a proper set of strain-dependent rate constants, the model fits well a broad range of experimental data. Owing to that the strain-stress relation is described by a set of ordinary differential equations, the model can be used for simulating complex 3D muscle contractions. 相似文献
33.
N. A. Koubassova S. Y. Bershitsky M. A. Ferenczi P. Panine T. Narayanan A. K. Tsaturyan 《Molecular Biology》2009,43(4):632-642
The interference fine structure of the M3 reflection in the low-angle X-ray diffraction patterns of muscle fibers is used
for the measurements of axial movements of myosin heads with a precision of 0.1–0.2 nm. We have measured changes in the M3
interference profile during tension rise induced by a 5°C to 30°C temperature jump in thin bundles of contracting fibers from
rabbit skeletal muscle. Interpreting the data with a point diffractor model gives an estimate for the axial movement of the
myosin heads during force rise of less than 0.6 nm. Modifications of the point diffractor model are discussed. We show that
our experimental data can be explained by a model where myosin heads bind actin in a number of structurally different states
either stereoor non-stereo-specifically. 相似文献