Mechanochemical coupling in spin-labeled, active, isometric muscle

Josh E. Baker, Leslie E.W. LaConte, Ingrid Brust-Mascher, David D Thomas

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Observed effects of inorganic phosphate (P(i)) on active isometric muscle may provide the answer to one of the fundamental questions in muscle biophysics: how are the free energies of the chemical species in the myosin- catalyzed ATP hydrolysis (ATPase) reaction coupled to muscle force? Pate and Cooke (1989. Pflugers Arch. 414:73-81) showed that active, isometric muscle force varies logarithmically with [P(i)]. Here, by simultaneously measuring electron paramagnetic resonance and the force of spin-labeled muscle fibers, we show that, in active, isometric muscle, the fraction of myosin heads in any given biochemical state is independent of both [P(i)] and force. These direct observations of mechanochemical coupling in muscle are immediately described by a muscle equation of state containing muscle force as a state variable. These results challenge the conventional assumption mechanochemical coupling is localized to individual myosin heads in muscle.

Original languageEnglish (US)
Pages (from-to)2657-2664
Number of pages8
JournalBiophysical journal
Issue number5
StatePublished - Nov 1999

Bibliographical note

Funding Information:
This work was supported by grants from the Muscular Dystrophy Association, the National Institutes of Health (AR32961), the Minnesota Supercomputer Institute, and the National Science Foundation.


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