Control of the orientation of photosynthetic reaction center proteins using an applied bias-voltage Langmuir-Blodgett technique

We investigated the orientation control of photosynthetic reaction center proteins (RCs) by preparing RC Langmuir-Blodgett films in which a DC bias voltage ranging from -0.5 V to +0.5 V was applied (using a potentiostat) during film deposition. The bias voltage was applied between a conductive indium-tin-oxide coated glass substrate and a subphase through a helical platinum counter electrode. The orientation was evaluated using displacement-current measurement and photoelectron spectroscopy. Our results confirm that molecular orientation of RCs in the films was controlled by the polarity of the applied voltage.