Groupe de Physique Statistique

Adsorption of biomolecules at interfaces is determined by an interplay of solvation forces and direct interations with with surface. There are no analytical models for the solvation forces in such complex systems, but atomistic simulations can describe all forces that determine surface adsorption. We study peptide adsorption forces and friction forces on a hydrophobic and a hydrophilic diamond surface by molecular dynamics simulations with explicit solvent. The analysis of the friction forces show that equilibrium conditions are achieved on the hydrophobic surfaces. The resulting free energies compare well with AFM experiments. The resulting free energy is decomposed into contributions of different origin. This decomposition reveals that the "hydration force" has several contributions that partly compensate. On hydrophilic surfaces, friction effects are stronger than on the hydrophobic surfaces, and the simulations cannot be done under equilibrium conditions. We present a thorough analysis of the friction effects on peptide motion on the hydrophilic and the hydrophobic surface.