Adsorption of the Flexible Salivary Proteins Statherin and PRP-1 to Negatively Charged Surfaces – A Monte Carlo Simulation and Ellipsometric Study

Abstract

The structural properties of the salivary proteins, acidic proline rich PRP-1 and statherin, adsorbed onto negatively charged surfaces have been studied by Monte Carlo simulations and ellipsometry. It is shown that both proteins adsorb to negatively charged surfaces, although their net charges are negative. Experimentally, an initial fast mass-controlled film build-up was detected for both proteins, and plateaus were reached within 10 min. The isotherm shape and the adsorbed amounts were similar for PRP-1 to hydrophilic and hydrophobic surfaces, while statherin adsorbs to a greater extent to the hydrophobic surface. These results could be explained from the simulation results by considering the proteins as diblock polyampholytes. It has also been shown that the adsorption of PRP-1 to a negatively charged surface may be purely electrostatically driven, while pure electrostatic interaction is not sufficient to drive adsorption of statherin,i.e., an extra short-ranged attractive interaction is necessary to account for the experimental observations.