ATP consumption in an actin-myosin network: Response functions in an NADH Assay

Actin-myosin networks are used in a wide variety of cellular tasks, including locomotion, structural reorganization, and cell signaling. These networks consist of actin biopolymers along which myosin motors bind to and step along the actin filaments. When these actin-myosin networks are crosslinked, they typically shrink uniformly to a small cluster. Using video analysis, we extract from these networks a strain rate: ε. We also couple the actin-myosin motor to a NADH fluorescence assay and compute the energy consumption density e from the decrease in NADH concentration. Dividing the strain rate by the energy consumption density gives a response function, which we call contraction efficiency, and allows a description of the contraction kinetics of the active gel. We present the regimes of contraction, as well as identifying the optimal conditions to maximize contraction efficiency in a freely contracting actin network.