RELATING CONTACT SURFACE HYDROPHOBICITY TO MOLECULAR EVENTS INFLUENCING BIOLOGICAL ADHESION

Quantification of the effects of selected contact surface properties o n kinetic rate constants that describe protein arrival and unfolding a t solid-liquid interfaces should aid our understanding of the nature o f biological adhesion. We observed that the product of rate constants defining protein arrival and conversion to an irreversibly adsorbed st ate increased with increasing surface hydrophobicity, while the rate c onstant defining desorption of protein from a reversibly adsorbed stat e apparently decreased. However, the hydrophobicity of a contact mater ial, as measured by the nondispersive component of the work required t o remove water from its surface, did not correlate with protein surfac e activity over the entire range of hydrophobicity tested. Our studies with silicon suggested that limited silanization with dichlorodimethy lsilane yielded an increased hydrophobicity, but no observable increas e in the entropic driving force for adsorption, i.e. no adsorption-enh ancing hydrophobic effect. Apparently, only a reduction in the potenti al for acid-base interaction occurred until increased silanization yie lded some minimal hydrophobicity, beyond which adsorption increased wi th increasing hydrophobicity.