(742e) Blinkers and Followers: Limit Cycles and Stability of Active Inclusions on Biological Interfaces

Active interfacial inclusions like membrane protein machines play fundamental roles in intracellular transport and force generation. These machines perform complex cellular tasks by binding, releasing, and changing conformations, inducing hydrodynamic flows in the membrane and the surrounding fluid. The disturbance flow associated with one such inclusion can advect others, and the collective effect can generate large-scale intracellular motion. We theoretically examine this collective behavior for particles or proteins bound to a viscous interface. Each inclusion generates a dipolar flow field to leading order, and the structure of the flow changes with interfacial and bulk viscosity and the degree of confinement due to depth of the surrounding fluid(s). Pairs of dipolar particles display a rich set of nonlinear dynamics, including modes where inclusions seemingly follow one another, or where relative orientations enter a limit cycle and ‘blink’ in an oscillatory manner. We illustrate the mechanistic origins of the observed nonlinear dynamics by simplifying to a system of analytically tractable coupled oscillators. The depth of the surrounding fluid has a profound effect on the stability of followers and blinkers, and confinement rapidly aggregates particles. We also perform computational studies to test large scale collective dynamics, revealing unique and controllable modes of phase behavior mediated by interfacial hydrodynamics. These results reveal novel experimental strategies to concentrate or isolate membrane inclusions using geometry and flow.