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SUMMARY:Mean-field crossbridge dynamics break down in frustration - Madhus
 udhan Venkadesan (Yale University)
DTSTART:20230907T111000Z
DTEND:20230907T113000Z
UID:TALK203878@talks.cam.ac.uk
DESCRIPTION:How actomyosin crossbridges share and transmit loads between t
 he thick and thin filaments in a sarcomere underlies the emergence of musc
 le's stimulus-dependent material properties. Following A.F. Huxley's work\
 , many sarcomere models treat the thick and thin filaments as rigid and lu
 mp their compliance into a single series elastic element. Under this appro
 ximation\, the crossbridges act as parallel elastic force generators. So t
 heir collective dynamics are captured by the ensemble mean. In this work\,
  we investigate the accuracy of this approximation by exactly accounting f
 or the spatially distributed filament and crossbridge compliances. We show
  that even the small degree of measured filament compliance in a sarcomere
  leads to a profound deviation of the mechanical behavior from the ensembl
 e mean. The lumped compliance approximation fails to capture a stiction-li
 ke state of activated muscle that is thought to underlie how animals are a
 ble to stiffen their joints through muscle co-contraction. Further analyse
 s show that crossbridge clusters may be favored because they lower the tot
 al system strain energy. We speculate that the spatial inhomogeneity of cr
 ossbridges has mechanochemical consequences that affect the development an
 d cycling of crossbridges in actomyosin networks. Specifically\, clusters 
 of persistent\, stalled crossbridges are predicted to emerge as a stable s
 tate for a frustrated ensemble and possibly explain transitions between a 
 fluid-like and solid-like state in muscle.
LOCATION:Seminar Room 1\, Newton Institute
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