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Large-scale Models Reveal the Two-component Mechanics of Striated Muscle
Formerly Institute of Plant Physiology, University of Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria
Received: 23 May 2008; in revised form: 11 December 2008 / Accepted: 15 December 2008 / Published: 18 December 2008
Abstract: This paper provides a comprehensive explanation of striated muscle mechanics and contraction on the basis of filament rotations. Helical proteins, particularly the coiled-coils of tropomyosin, myosin and α-actinin, shorten their H-bonds cooperatively and produce torque and filament rotations when the Coulombic net-charge repulsion of their highly charged side-chains is diminished by interaction with ions. The classical “two-component model” of active muscle differentiated a “contractile component” which stretches the “series elastic component” during force production. The contractile components are the helically shaped thin filaments of muscle that shorten the sarcomeres by clockwise drilling into the myosin cross-bridges with torque decrease (= force-deficit). Muscle stretch means drawing out the thin filament helices off the cross-bridges under passive counterclockwise rotation with torque increase (= stretch activation). Since each thin filament is anchored by four elastic α-actinin Z-filaments (provided with forceregulating sites for Ca2+ binding), the thin filament rotations change the torsional twist of the four Z-filaments as the “series elastic components”. Large scale models simulate the changes of structure and force in the Z-band by the different Z-filament twisting stages A, B, C, D, E, F and G. Stage D corresponds to the isometric state. The basic phenomena of muscle physiology, i. e. latency relaxation, Fenn-effect, the force-velocity relation, the length-tension relation, unexplained energy, shortening heat, the Huxley-Simmons phases, etc. are explained and interpreted with the help of the model experiments.
Keywords: Muscle contraction; muscle mechanics; rotating filaments
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Jarosch, R. Large-scale Models Reveal the Two-component Mechanics of Striated Muscle. Int. J. Mol. Sci. 2008, 9, 2658-2723.
Jarosch R. Large-scale Models Reveal the Two-component Mechanics of Striated Muscle. International Journal of Molecular Sciences. 2008; 9(12):2658-2723.
Jarosch, Robert. 2008. "Large-scale Models Reveal the Two-component Mechanics of Striated Muscle." Int. J. Mol. Sci. 9, no. 12: 2658-2723.