  Computer simulations can aid in understanding how collective materials
properties emerge from interactions between simple constituents. Here, we
introduce a coarse-grained model that enables simulation of networks of actin
filaments, myosin motors, and crosslinking proteins at biologically relevant
time and length scales. We demonstrate that the model qualitatively and
quantitatively captures a suite of trends observed experimentally, including
the statistics of filament fluctuations, mechanical responses to shear, motor
motilities, and network rearrangements. We use the simulation to predict the
viscoelastic scaling behavior of crosslinked actin networks, characterize the
trajectories of actin in a myosin motility assay, and develop order parameters
to measure contractility of a simulated actin network. The model can thus serve
as a platform for interpretation and design of cytoskeletal materials
experiments, as well as for further development of simulations incorporating
active elements.
