The control of biofilm formation is a challenging goal that has not been reached yet in many aspects. One is the role of van der Waals forces and another the importance of mutual interactions between the adsorbing and the adsorbed biomolecules (criti
cal crowding). Here, a combined exeperimental and theoretical approach is presented that fundamentally probes both aspects. On three model proteins, lysozyme, {alpha}-amylase and bovine serum albumin (BSA), the adsorption kinetics is studied. Composite substrates are used enabling a separation of the short- and the long-range forces. Though usually neglected, experimental evidence is given for the influence of van der Waals forces on the protein adsorption as revealed by in situ ellipsometry. The three proteins were chosen for their different conformational stability in order to investigate the influence of conformational changes on the adsorption kinetics. Monte Carlo simulations are used to develop a model for these experimental results by assuming an internal degree of freedom to represent conformational changes. The simulations also provide data on the distribution of adsorption sites. By in situ atomic force microscopy we can also test this distribution experimentally which opens the possibility to e.g. investigate the interactions between adsorbed proteins.
Hydrodynamic slippage plays a crucial role in the flow dynamics of thin polymer films, as recently shown by the analysis of the profiles of liquid fronts. For long-chained polymer films it was reported that a deviation from a symmetric profile is a r
esult of viscoelastic effects. In this Letter, however, evidence is given that merely a slip boundary condition at the solid/liquid interface can lead to an asymmetric profile. Dewetting experiments of entangled polymer melts on diverse substrates allow a direct comparison of rim morphologies. Variation of molecular weight Mw clearly reveals that slippage increases dramatically above a certain Mw and governs the shape of the rim. The results are in accordance with the theoretical description by de Gennes.
