Protein interaction with surfaces: Separation distance-dependent interaction energies

Abstract

A computational method was used to calculate the distance-dependent adsorption energies of three proteins, immunoglobulin Fab, trypsin, and lysozyme, on polyethylene, polypropylene, and poly(vinyl alcohol) surfaces. Two different protein orientations for each protein were used to calculate the interaction energy as a function of the separation distance. The programs developed in our laboratory considered van der Waals, electrostatic, and solvation interaction energies. Our computer simulation study suggests that the protein adsorption energy on three polymer surfaces is determined mainly by the relative importance of the attractive van der Waals interaction. The minimum and maximum total adsorption energies calculated in our study were −15.65 kJ/mol for lysozyme on polypropylene and −181.66 kJ/mol for trypsin on polypropylene. The total energy was dependent on the orientation of a protein even on the same polymer surface as expected. The smallest difference between the adsorption energies of the two orientations was 2.03 kJ/mol for trypsin on poly(vinyl alcohol) and the largest difference was 137.93 kJ/mol for lysozyme on poly(vinyl alcohol). Electrostatic and solvation interaction energies showed both attractive and repulsive interaction energies depending on the protein orientation. The simulation study shows that the protein–surface interaction becomes negligible, when the distance between them exceeds 20–30 Å. The distance at which the total interaction energy becomes −2 kJ/mol varied between 9.37 and 24.70 Å for lysozyme on polyethylene and trypsin on poly(vinyl alcohol), respectively. Our results indicate that the grafting of short hydrophilic polymer chains may be enough to prevent protein adsorption.