Enhanced Diffusion by Reversible Binding to Active Polymers

Cells
are known to use reversible binding to active biopolymer
networks to allow diffusive transport of particles in an otherwise
impenetrable mesh. We here determine the motion of a particle that
experiences random forces during binding and unbinding events while
being constrained by attached polymers. Using Monte Carlo simulations
and a statistical mechanics model, we find that enhanced diffusion
is possible with active polymers. However, this is possible only under
optimum conditions that has to do with the relative length of the
chains to that of the plate. For example, in systems where the plate
is shorter than the chains, diffusion is maximum when many chains
have the potential to bind but few remain bound at any one time. Interestingly,
if the chains are shorter than the plate, we find that diffusion is
maximized when more active chains remain transiently bound. The model
provides insights into these findings by elucidating the mechanisms
for binding-mediated diffusion in biology and design rules for macromolecular
transport in transient synthetic polymers.