Effect of Hydrophobic Groups on Adsorption of Amino Acids to Solid Surfaces in Water

We calculated the free energies of adsorption between a solid wall and various arginine derivatives in water using molecular dynamics simulations. We varied the hydrophobic group size of the amino acids in two ways and the hydrophilicity of the solid wall in five ways. The free energy of adsorption decreased by increasing the hydrophilicity of the solid wall, regardless of the size of the hydrophobic group. Amino acids with small hydrophobic groups adsorbed on the solid wall with the strongest hydrophilicity, but the free energy of the amino acids with large hydrophobic groups was relatively small. The free energy of adsorption in benzene solvent increased by increasing hydrophilicity of the solid wall, yet analogously to results in water solvent was independent of the size of the hydrophobic group. We attribute these differences in free energy to the effect of solvent molecules localized on the solid wall. Thus, these results may modulate peptide adsorption on a solid surface by the size of the peptide’s hydrophobic groups.