Strain Response to Energy Consumption in Contractile Acto-Myosin Gels

Acto-myosin networks are used by living cells for essential functions such as locomotion, structural reorganization, and mechanical feedback. To accomplish these tasks these networks often adopt a disordered mesh-like structure that experiences deformation, or strain, through myosin motors consuming ATP and sliding actin filaments past each other. Previous work has measured the mechanical response of these acto-myosin networks to external stresses, however the response to myosin-driven ATPase activity remains poorly understood. What is the relationship between the energy consumed and the strain observed in these networks? We present the first direct simultaneous measurements of ATP consumption and strain in a reconstituted in-vitro acto-myosin network. This is achieved through dual-channel observation of an acto-myosin network with an NADH assay that couples ATP consumption to fluorescence output. We systematically vary myosin and crosslinking protein concentrations to determine which network conditions create an optimal strain response. Our work establishes a novel method of characterizing the mechanical response of contractile active gels to internal driving, and will allow for future studies that quantify how contractile strain measurements affect molecular motor activity through biochemical regulatory feedback.