Seminarium Fizyki Materii Skondensowanej

Protein adsorption studies are plagued by many confusions andmisinterpretations stemming from the abandonment of basic physics. Therefore, contrary to common views, the thesis of a dominant role ofCoulomb electrostatic interactions in protein adsorption phenomena is formulated. In order to prove this, a combination of theoretical anddirect, in situ experimental methods are implemented. In theoreticalmodeling emphasis is focused on coarse-grained methods, exploiting theefficient bead models of protein molecules. Using this approach basichydrodynamic properties of protein molecules, such as the diffusion tensor,hydrodynamic diameters and intrinsic viscosities are calculated using thelinear Stokes equation. Additionally, the surface blocking functions andjamming coverages for such model shapes are determined using the random sequential adsorption (RSA) simulations. Knowing the jamming coverage and blocking functions boundary conditions for bulk transport equations are formulated. Solutions of these equations for the convection and diffusion-controlled transport are discussed. The theoretical results areexploited for the interpretation of protein adsorption kinetics studied byAFM and in situ electrokinetic methods (streaming potential,microelectrophoresis). Application of such hybrid approaches enabled oneto quantitatively determine protein adsorption mechanisms on varioussubstrates including polymeric microparticles (polystyrene latexes). It is shown that protein adsorption is mainly governed by the discreteelectrostatic interactions among ion pairs with negligible role of otherinteraction types. Anomalous adsorption of proteins at surfaces bearinglike surface charges, where the classical, mean-field theories fail, isexplained in terms of heterogeneous charge distributions on proteinmolecules. By exploiting these experimental data, the validity of thecoarse grained approaches combined with solutions of the continuityequation for quantitatively predicting protein adsorption kinetics isconfirmed.