Complex desorption of mucin from silica.

Complex solutes may adsorb from solution onto solid surfaces in a concentration-dependent manner. In other words, the adsorption behavior is qualitatively different in different bulk concentration regimes. Here we show that the large glycoprotein mucin not only adsorbs in distinctively different ways according to the bulk concentration but also, strikingly, that the law of desorption, established with the help of high-resolution molecular microscopy, depends on the bulk concentration during adsorption. Making use of supporting bulk rheology data delineating the entangled regime and atomic force microscopy images of the adsorbed layers corroborating the existence of a bilayer structure formed at higher bulk concentrations, a tentative molecular mechanism for the observations is proposed.