FIBRONECTIN ADSORPTION TO SURFACES OF HYDRATED CRYSTALS - AN ANALYSIS OF THE IMPORTANCE OF BOUND WATER IN PROTEIN SUBSTRATE INTERACTIONS

We have shown that fibronectin, one of the major cell adhesion promoting proteins, is adsorbed with markedly different affinities to the organized surfaces of different crystals, containing a controlled and known amount of surface-bound water molecules. Fibronectin adsorbed maximally to the purely ionic surfaces of calcite, that do not include lattice water molecules. It did not adsorb at all on the prevalent faces of brushite, that expose to solution a continuous layer of structured lattice water. In other systems including calcium (RR)-tartrate tetrahydrate and calcium fumarate trihydrate, fibronectin adsorption gradually decreased as the amount of lattice water molecules on the crystal surface increased. It is thus apparent that the presence of surface bound water may be instrumental in modulating protein adsorption to surfaces. The use of crystals as substrates permits clear-cut conclusions to be reached on the molecular requirements for protein adsorption to surfaces, that were not accessible with conventional substrates.