Measuring active nematic fields in an in vitro actomyosin system

Self-organization of cytoskeletal active matter is at the core of essential processes in living systems, including chromosome segregation by microtubules, cell migration, and cell division through the actomyosin cortex. Despite numerous discrete and continuous theories—most notably active gel theory— connections between these theories and experimental observations in the actomyosin cortex that capture both the orientational and number density dynamics of constituents have been challenging to achieve.

To bridge this gap, we conduct in vitro experiments that involve preparing actin filaments on a lipid bilayer, combined with an energy mix and the catalyst VCA to counteract myosin-driven disassembly. We then add myosin II motors and observe the contractile dynamics of the actomyosin system via spinning disk microscopy.

We extract density, velocity, and director fields and analyze the correlations among these fields to quantify the significance of active alignment, flow coupling, and advection. This effort represents a step toward establishing a quantitative framework that connects active nematic field theories with controlled in vitro actomyosin experiments.