Before revision:  We also find that in rigid environments, symmetric myosin II minifilaments perform a random walk with an effective diffusion constant which decreases with increasing ensemble size, in marked contrast to the behavior of ensembles of processive motors that function in cargo transport .
After revision:  We also find that in rigid environments, symmetric myosin II minifilaments perform a random walk with an effective diffusion constant which decreases with increasing ensemble size, as demonstrated for rigid substrates with an analytical treatment .