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

We have shown that fibronectin, one of the major cell adhesion promoti ng proteins, is adsorbed with markedly different affinities to the org anized surfaces of different crystals, containing a controlled and kno wn amount of surface-bound water molecules. Fibronectin adsorbed maxim ally to the purely ionic surfaces of calcite, that do not include latt ice water molecules. It did not adsorb at all on the prevalent faces o f brushite, that expose to solution a continuous layer of structured l attice water. In other systems including calcium (RR)-tartrate tetrahy drate and calcium fumarate trihydrate, fibronectin adsorption graduall y decreased as the amount of lattice water molecules on the crystal su rface increased. It is thus apparent that the presence of surface boun d water may be instrumental in modulating protein adsorption to surfac es. The use of crystals as substrates permits clear-cut conclusions to be reached on the molecular requirements for protein adsorption to su rfaces, that were not accessible with conventional substrates.