Quasi-Elastic Light Scattering Studies of Muscular Contraction
For the past quarter of a century studies of the molecular mechanism of muscular contraction have been guided by the sliding filament model of striated muscle. According to this model myosin cross-bridges projecting from the myosin thick filaments interact with the actin thin filaments of the muscle cell in such a way that each cross-bridge produces an impulsive contractile force between the interdigitating thick and thin filaments. Each thick filament contains a few hundred cross-bridges which attach to the thin filament independently and asynchronously so that collectively they produce an average contractile force that depends linearly on the extent to which the thick and thin filaments overlap. Much of what is known about the molecular dynamics of the cross-bridge cycle is derived from low angle x-ray diffraction studies of contracting muscle and is subject to the limitations inherent in space-time average measurements on a dynamic process. There is currently an active search for more direct evidence to corroborate the independent cycling of cross-bridges.1,2 We have been using quasi-elastic light scattering to obtain evidence for cross-bridge cycling.3,4 Our most recent results obtained on single muscle fibers, are free of many of the complicating factors present in our early work on whole muscle and it is these new results that are presented here.
KeywordsThin Filament Fiber Axis Sarcomere Length Contracting Muscle Thick Filament
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