Understanding intercellular interactions and cell adhesion: lessons from studies on protein-metal interactions.

To understand cell-cell interactions and the interactions of cells to non-biological materials, studies on binding forces between cellular proteins and between proteins and non-biological material such as metal surfaces are essential. The adsorption of proteins to solid-water interfaces is a multifactorial and a multistep process. First steps are determined by long-range interactions where surface properties such as hydrophobicity, distribution of charged groups, ion concentrations and pH play important roles. In later steps structural rearrangements in the protein molecule and dehydration effects become more important making the adsorption process often irreversible. In the following we demonstrate that protein A and tubulin have a specific type of interaction to metal surfaces probably as an intermediate step in the adsorption process. The proteins were attached to the tip of a microfabricated cantilever in such a way that only one molecule interacts with the surface. By recording force-distance curves with an atomic force microscope the adhesion forces of single molecules binding to gold, titanium and indium-tinoxid surfaces were measured.