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Effect of strain on actomyosin kinetics in isometric muscle fibers.

Siththanandan, V. B. and Donnelly, J. L. and Ferenczi, M. A. (2006) 'Effect of strain on actomyosin kinetics in isometric muscle fibers.', Biophysical journal., 90 (10). pp. 3653-3665.


Investigations were conducted into the biochemical and mechanical states of cross-bridges during isometric muscle contraction. Rapid length steps (3 or 6 nm hs–1) were applied to rabbit psoas fibers, permeabilized and isometric, at either 12°C or 20°C. Fibers were activated by photolysis of P3-1-(2-nitrophenyl)-ethyl ester of ATP infused into rigor fibers at saturating Ca2+. Sarcomere length, tension, and phosphate release were recorded—the latter using the MDCC-PBP fluorescent probe. A reduction in strain, induced by a rapid release step, produced a short-lived acceleration of phosphate release. Rates of the phosphate transient and that of phases 3 and 4 of tension recovery were unaffected by step size but were elevated at higher temperatures. In contrast the amplitude of the phosphate transient was smaller at 20°C than 12°C. The presence of 0.5 or 1.0 mM added ADP during a release step reduced both the rate of tension recovery and the poststep isometric tension. A kinetic scheme is presented to simulate the observed data and to precisely determine the rate constants for the elementary steps of the ATPase cycle.

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Record Created:12 Feb 2009
Last Modified:08 Apr 2009 16:31

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