(572f) A Brownian Dynamics Study of Protein Deposition On a Solid Surface

When protein molecules deposit at a water-solid interface, they have been observed to form 1-dimensional short strings or 2-dimension dendrites that are one-protein molecule wide. These stringy structures are different from those predicated on random sequential adsorption and indicate the presence of other mechanisms during protein deposition. In this work, we simulate protein deposition on a neutral solid surface with Brownian dynamics simulations. A protein molecule is treated as a charged sphere and interacts with other protein molecules through DLVO theory, which combines the effects of Hamaker (van der Waals) attraction and electrostatic repulsion. The structure of the deposited protein is examined through simulation snapshots, radial distribution function, order parameter, and analysis of coordination number. Depending on the ionic strength and the protein surface charge, the protein-protein interaction can vary from purely attractive to the type with repulsive energy barrier. It is found that protein-protein interactions with repulsive energy barrier lead to slower clustering rate but promote the formation of stringy structures while purely attractive protein-protein interaction leads to faster clustering but more compact structures. The roles of homogeneous and heterogeneous growth mechanisms in protein deposition and cluster formation are also studied.