Abstract
The surface of mammalian cells, i.e. the plasma membrane and the underlying cytoskeletal cortex, constitutes an active platform for many cellular processes including cargo uptake, signaling and formation of cell adhesions. Experimental and theoretical work has recently shown that acto-myosin dynamics can modify the local membrane organization, but the molecular details are not well understood. Here, we demonstrate the potential of iSCAT microscopy, a label free imaging technique, to interrogate single molecule processes in the context of mesoscale dynamics. In a minimal acto-myosin network linked to supported lipid bilayers, we measure single actin and myosin II filament dynamics as well as whole network flow and organization. We show that the binding kinetics and processivity of myosin II filaments vary with the ATP concentration and identify a regime that promotes whole network contractility. This combination of techniques provides an ideal tool to bridge multiple length scales ranging from single myosin head binding kinetics up to network contraction on the mesoscopic scale, and we believe that this approach will be useful for the investigations of multi-component systems.
