A kinetic model of partially reversible protein adsorption

We present a kinetic adsorption model for proteins that accounts for the experimentally observed properties of partial reversibility and surface induced conformational change. Particles (proteins) are modeled as disks that adsorb sequentially and without overlap at random positions onto a surface. Following adsorption, a particle can either desorb or spread symmetrically to a larger size. If the latter occurs, it remains adsorbed irreversibly. Both of these events obey first order kinetic rate laws. We derive analytical results in the asymptotic regime and report Monte Carlo results for shorter times. This model yields adsorbed phases that are more dense than those predicted by models of purely irreversible adsorption. We attribute this densification to a fluid structure that is quite liquidlike. We show that a number of experimentally observed kinetic behaviors can be reproduced with this model and that it is in good quantitative agreement with recent experiments. (C) 1997 American Institute of Physics.