Annals of Biomedical Engineering

, Volume 32, Issue 11, pp 1559–1568

A Spatially Explicit Nanomechanical Model of the Half-Sarcomere: Myofilament Compliance Affects Ca2+-Activation

  • P. Bryant Chase
  • J. Michael Macpherson
  • Thomas L. Daniel

DOI: 10.1114/B:ABME.0000049039.89173.08

Cite this article as:
Chase, P.B., Macpherson, J.M. & Daniel, T.L. Annals of Biomedical Engineering (2004) 32: 1559. doi:10.1114/B:ABME.0000049039.89173.08


The force exerted by skeletal muscle is modulated by compliance of tissues to which it is connected. Force of the muscle sarcomere is modulated by compliance of the myofilaments. We tested the hypothesis that myofilament compliance influences Ca2+ regulation of muscle by constructing a computational model of the muscle half sarcomere that includes compliance of the filaments as a variable. The biomechanical model consists of three half-filaments of myosin and 13 thin filaments. Initial spacing of motor domains of myosin on thick filaments and myosin-binding sites on thin filaments was taken to be that measured experimentally in unstrained filaments. Monte-Carlo simulations were used to determine transitions around a three-state cycle for each cross-bridge and between two-states for each thin filament regulatory unit. This multifilament model exhibited less “tuning” of maximum force than an earlier two-filament model. Significantly, both the apparent Ca2+-sensitivity and cooperativity of activation of steady-state isometric force were modulated by myofilament compliance. Activation-dependence of the kinetics of tension development was also modulated by filament compliance. Tuning in the full myofilament lattice appears to be more significant at submaximal levels of thin filament activation.

Muscle Actin filament Myosin filament Cross- bridge Troponin Tropomyosin Calcium regulation Force Kinetics of tension development 

Copyright information

© Biomedical Engineering Society 2004

Authors and Affiliations

  • P. Bryant Chase
    • 1
  • J. Michael Macpherson
    • 2
  • Thomas L. Daniel
    • 3
  1. 1.Department of Biological Science and Program in Molecular BiophysicsFlorida State UniversityTallahassee
  2. 2.Department of Biological SciencesStanford UniversityStanford
  3. 3.Department of BiologyUniversity of WashingtonSeattle

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