Design of supported membranes tethered via metal-affinity ligand-receptor pairs

Model lipid layers are very promising in investigating the complex network of recognition, transport and signaling processes at membranes. We have dev eloped a novel and generic approach to create supported lipid membranes tet hered by metal-affinity binding. By self-assembly we have generated various interfaces that display histidine sequences (6xHis) via polymer spacers. T hese histidine-functionalized interfaces are designed to allow specific doc king and fusion of vesicles containing metal-chelating lipids. By means of surface plasmon resonance and atomic force microscopy we analyzed the forma tion and subsequently the structure of these solid-supported membranes. Alt hough the affinity constant of single ligand-receptor pairs is only in the micromolar range, very stable immobilization of these membranes was observe d. This behavior can be explained by multivalent interactions resembling ma ny features of cell adhesion. The process is highly specific, because vesic le docking and bilayer formation are strictly dependent on the presence of metal-affinity ligand-receptor pairs. The surface accessibility and geometr y of these tethered membranes were probed by binding of histidine-tagged po lypeptides. The supported membranes show adsorption kinetics and values sim ilar to planar supported monolayers. Using various combinations of metal-ch elating and histidine-tagged lipids or thiols these metal-affinity-tethered membranes should make a great impact on probing and eventually understandi ng the dynamic dialog of reconstituted membrane proteins.