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Updated: May 13, 2026

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
Published on: May 4, 2022
The stiffness of myosin subfragment-1 changes with the physiological state of muscle
1Dept. of Biochemistry and Molecular Biology, Ferrara University, Via Borsari 46, 44121 Ferrara, Italy. enrico.grazi@unife.it
Abstract:
The anisotropy decay of the spin-labelled myosin subfragment-1, takes place with different rates depending on the physiological state of muscle: relaxation, isometric contraction and rigor. The decay is mostly explained by the rotation of myosin subfragment-1. This rotation is promoted by thermal energy and is opposed by the viscous and by the elastic reactions. A model is proposed that relates the amplitude of the rotation of myosin subfragment-1 to its stiffness. It is found that the amplitude of the rotation is inversely proportional to the stiffness assigned to the structure. It is concluded that, in relaxed myofibrils, the stiffness of myosin subfragment-1 is much lower than that in myosin subfragment-1 - F-actin. The consequences of this finding on modeling of muscle contraction are discussed.
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