  The polymerization of actin via branching at a cell membrane containing
nucleation-promoting factors is simulated using a stochastic-growth
methodology. The polymerized-actin distribution displays three types of
behavior: a) traveling waves, b) moving patches, and c) random fluctuations.
Increasing actin concentration causes a transition from patches to waves. The
waves and patches move by a treadmilling mechanism which does not require
myosin II. The effects of downregulation of key proteins on actin wave behavior
are evaluated.
