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Related Experiment Videos

Estimation of cross-bridge stiffness from maximum thermodynamic efficiency.

C J Barclay1

  • 1Department of Physiology, Monash University, Clayton, Victoria, Australia. chris.barclay@med.monash.edu.au

Journal of Muscle Research and Cell Motility
|February 27, 1999
PubMed
Summary

This study estimates myosin cross-bridge stiffness in frog muscle using thermodynamic efficiency. Realistic stiffness values were found to be higher than those from isolated protein studies.

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Area of Science:

  • Muscle physiology
  • Biophysics
  • Skeletal muscle mechanics

Background:

  • Muscle contraction relies on myosin cross-bridges interacting with actin filaments.
  • Cross-bridge mechanical properties, specifically stiffness, dictate the work performed during each cycle.
  • Understanding cross-bridge mechanics is crucial for elucidating muscle function.

Purpose of the Study:

  • To estimate the stiffness of myosin cross-bridges in frog sartorius muscle.
  • To compare stiffness values derived from thermodynamic efficiency with those from other experimental methods.
  • To investigate the influence of model assumptions on stiffness estimations.

Main Methods:

  • Utilized a two-state cross-bridge model to estimate stiffness from thermodynamic efficiency (work/free energy change).

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  • Assumed constant cross-bridge stiffness and tight-coupling between cross-bridge cycles and ATP utilization.
  • Reviewed literature values for maximum thermodynamic efficiency in frog sartorius muscle.

    • Main Results:

    • The model accurately predicted mechanical efficiency (work/enthalpy output).
    • Realistic cross-bridge stiffness values (1-2.2 pN nm-1) were estimated for power stroke amplitudes of 10-15 nm.
    • Estimated stiffness aligns with quick-release experiments but exceeds values from isolated protein studies.

    Conclusions:

    • Thermodynamic efficiency provides a viable method for estimating cross-bridge stiffness in muscle.
    • Inclusion of external compliance is necessary when comparing with quick-release experiments.
    • Further investigation into cross-bridge states and coupling assumptions is warranted.