Molecular Simulation Studies of Protein Interactions with Zwitterionic Phosphorylcholine Self-Assembled Monolayers in the Presence of Water

Molecular simulations were performed to study the interactions between a protein (lysozyme, LYZ) and phosphorylcholine-terminated self-assembled monolayers (PC-SAMs) in the presence of explicit water molecules and ions. The results show that the water molecules above the PC-SAM surface create a strong repulsive force on the protein as it approaches the surface. The structural and dynamic properties of the water molecules above the PC-SAM surface were analyzed to provide information regarding the role of hydration in surface resistance to protein adsorption. It can be seen from residence time dynamics that the water molecules immediately above the PC-SAM surface are significantly slowed down as compared to bulk water, suggesting that the PC-SAM surface generates a tightly bound, structured water layer around its head groups. Moreover, the orientational distribution and reorientational dynamics of the interfacial water molecules near the PC-SAM surface were found to have the ionic solvation nature of the PC head groups. These properties were also compared to those obtained previously for an oligo(ethylene glycol) (OEG) SAM system and bulk water.