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Relation between the mechanical properties of muscles and their structure on the molecular level. (English) Zbl 1009.92006

From the introduction: It is well known that muscle contraction is a result of the relative movement of the interdigitating filaments: thick, containing myosin, and thin, containing actin. Recent studies indicate that the interaction between myosin heads and actin filaments, coupled with ATP hydrolysis and regulated by \(\text{Ca}^{2+}\), is a decisive event in muscle contraction. Moreover, it is well established that the actin-myosin interaction is highly stereospecific. That means that during contraction the cross-bridges, which cyclically protrude from the thick filament backbone towards surrounding thin filaments, have to provide into close contact thousands of the specific binding-sites on actin monomers and myosin heads. The cross-bridge movement is conditioned, of course, by a manner of packing of the myosin molecules into the thick filaments and the actin monomers into the thin filaments. On the other side, force generated during muscle contraction depends on the way of the cross-bridge movements. So, the mechanical properties of the muscles necessary to understand the muscle structure on the molecular level should be taken into consideration.
The main differences between our model and those proposed so far consist in two features. First, we have introduced the arrangement of the myosin tails along a helical track instead of the straight tails running nearly parallel to the filament axis. Second, instead of the symmetrical alignment of three cross-bridges in a crown, we have proposed an asymmetrical configuration. The new model provides not only the required geometrical accuracy, it also helps to better understand a number of mechanical properties of the muscles.

MSC:

92C10 Biomechanics
92C40 Biochemistry, molecular biology
92C30 Physiology (general)
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