Electron Transfer to Light-Activated Photosynthetic Reaction Centers from Rhodobacter sphaeroides Reconstituted in a Biomimetic Membrane System

Photosynthetic reaction centers (RCs) from Rb. sphaeroides with a genetically engineered 7-his-tag at the C-terminus of the M-subunit are bound to a Ni-NTA-modified gold surface. Subsequently, the bound RCs are subjected to in situ dialysis in the presence of lipid micelles to form a protein-tethered lipid bilayer membrane (ptBLM). Redox properties of the RC thus immobilized are investigated by cyclic voltammetry. Photocurrrents are generated in the range of 10 μA cm−2, however, different from previous studies at potentials of −200 and −300 mV, and without cytochrome c as a mediator. The unexpected behavior is explained in terms of an interprotein reaction between RC molecules promoted by the lipid bilayer, which we had previously detected by surface-enhanced infrared absorption spectroscopy.