Nonlinear microscale mechanics and macromolecular mobility of tunable cytoskeleton composites

Actin and microtubules are two key protein filaments that comprise the cytoskeleton, enabling cells to exhibit multifunctional nonlinear mechanics. However, it remains an open question as to how the structure, interactions, and dynamics of these proteins map to the nonlinear and non-equilibrium mechanics that the cytoskeleton exhibits. We address this open problem by using a robust approach that combines: tunable in vitro cytoskeleton networks, rheology that spans from molecular to mesoscopic scales, and single-molecule transport and mobility measurements. Specifically, we use optical tweezers microrheology to characterize the nonlinear mechanics of cytoskeleton networks while simultaneously using fluorescence microscopy and particle-tracking to determine macromolecular mobility and network stress propagation. To directly map network properties to stress response, we perform measurements using custom-designed in vitro networks of actin and microtubules with structural properties and interactions that can be precisely tuned. I will describe these methods as well as our recent intriguing results that demonstrate the elegant couplings that can emerge between network structure, stress response, and macromolecular mobility in cytoskeleton networks.