The reversible oriented immobilization of proteins on solid surfaces is a prerequisite for the investigation of mol. interactions at interfaces or the construction of supramol. assemblies. We demonstrate a generally applicable method using a synthetic chelator thioalkane which can self-assemble on a gold surface via its thiol group. It exposes its nitrilotriacetic acid group which serves as a chelator for transition metal ions. Reversible binding of a Fab fragment modified with a C-terminal hexahistidine extension was monitored in situ using surface plasmon resonance. The directed immobilization of proteins on surfaces opens new ways for structural investigations of proteins and the development of biosensors. [on SciFinder (R)]