The actomyosin cytoskeleton is an active semi-flexible polymer network whose non-equilibrium behaviors regulate both cell elasticity and fluidity to maintain or change cell shape. Unlike the induction of contractile flows, the maintenance of dynamic stability in highly labile yet internally pre-stressed active materials remains unknown. To this end , we synthesize a biomimetic active nematic liquid crystal from long semi-flexible actin filaments driven out-of-equilibrium by myosin motor activity. We identify new actomyosin interactions that govern the dynamic architecture and mechanical response of the network to active stresses. These responses include dynamic steady states, in which myosin induces transverse plucking of actin filaments, whose curvatures show anomalous and strongly coupled fluctuations across a broad spectrum of filament bending modes. These fluctuations break detailed balance, yet promote dynamic stability in a network predisposed to instabilities. Furthermore, the actomyosin interactions that maintain dynamic stability are fundamentally distinct from those that drive contractile flows of actomyosin networks.
The actin cytoskeleton is an active semi-flexible polymer network whose non-equilibrium properties coordinate both stable and contractile behaviors to maintain or change cell shape. While myosin motors drive the actin cytoskeleton out-of-equilibrium, the role of myosin-driven active stresses in the accumulation and dissipation of mechanical energy is unclear. To investigate this , we synthesize an actomyosin material in vitro whose active stress content can tune the network from stable to contractile. Each increment in activity determines a characteristic spectrum of actin filament fluctuations which is used to calculate the total mechanical work and the production of entropy in the material. We find that the balance of work and entropy does not increase monotonically and, surprisingly, the entropy production rate is maximized in the non-contractile, stable state. Our study provides evidence that the origins of system entropy production and activity-dependent dissipation arise from disorder in the molecular interactions between actin and myosin
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actomyosin
actin
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behaviors regulate both cell elasticity and fluidity
properties coordinate both stable and contractile behaviors
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Unlike the induction of contractile flows, the maintenance of dynamic stability in highly labile yet internally pre-stressed active materials remains unknown. To this end
While myosin motors drive the actin cytoskeleton out-of-equilibrium, the role of myosin-driven active stresses in the accumulation and dissipation of mechanical energy is unclear. To investigate this
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a biomimetic active nematic liquid crystal from long semi-flexible actin filaments driven out-of-equilibrium by myosin motor activity. We identify new actomyosin interactions that govern the dynamic architecture and mechanical response of the network to active stresses. These responses include dynamic steady states, in which myosin induces transverse plucking of actin filaments, whose curvatures show anomalous and strongly coupled fluctuations across a broad spectrum of filament bending modes. These fluctuations break detailed balance, yet promote dynamic stability in a network predisposed to instabilities. Furthermore, the actomyosin interactions that maintain dynamic stability are fundamentally distinct from those that drive contractile flows of actomyosin networks.
an actomyosin material in vitro whose active stress content can tune the network from stable to contractile. Each increment in activity determines a characteristic spectrum of actin filament fluctuations which is used to calculate the total mechanical work and the production of entropy in the material. We find that the balance of work and entropy does not increase monotonically and, surprisingly, the entropy production rate is maximized in the non-contractile, stable state. Our study provides evidence that the origins of system entropy production and activity-dependent dissipation arise from disorder in the molecular interactions between actin and myosin