Lattice model calculations of interactions between proteins and surface grafted polymers with tethered affinity ligands

Monte Carlo calculations of protein binding to affinity ligands tethered to a surface by polymers have been done and analyzed with statistical mechanical perturbation theory. The interaction of the polymers with the surface, the solvent and the protein has been varied. Different solution conditions of the polymers have been investigated, varying from collapsed polymer structures on a surface to structures extending out in the solution (athermic condition) or to mushroom like structures (hydrophobic polymers grafted on hydrophilic surface). The variation in binding of model proteins of different sizes and interactions with polymers has been studied. In general, smaller proteins bind better than larger proteins. Two types of polymer collapses have been studied. One type is due to increased polymer-surface attraction. The second type is due to increased polymer-self attraction. In the former case the binding, as a function of degree of collapse, decreases monotonically except for small proteins with attraction to the polymer. For collapses of the second type the loss of binding goes through a maximum except for large proteins.