Biomolecular Electronics: Vectorial Arrays of Photosynthetic Reaction Centers

Two-dimensional vectorial arrays of functional Photosystem I reaction centers have been prepared on atomically flat derivatized gold surfaces. The nature and extent of orientation were controlled by chemical modification of the surface derivative. For mercaptoacetic acid, 83% of the electron transport vectors were parallel to the surface, whereas with 2-mercaptoethanol 70% were oriented perpendicularly in the ``up'' position and only 2% were in the ``down'' position. No preferential orientation was observed with 2-dimethylaminoethanethiol.