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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|Publisher Web site:||http://dx.doi.org/10.1529/biophysj.105.072413|
|Record Created:||12 Feb 2009|
|Last Modified:||08 Apr 2009 16:31|
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