Bacteriorhodopsin monolayers for optoelectronics: Orientation and photoelectric response on solid supports

The bacteriorhodopsin (bR) monolayers were prepared by a self-assembly procedure on a solid surface. The orientation of monolayers on an Al substrate was determined using a Kelvin probe. The good orientation of purple membrane (PM) patches to the electrostatic asymmetry between the two sides of the membrane protein was described. Such monolayers, made from WT bR, exhibited a photoelectric response that was quite different from that of the bR multilayer and the bR suspension. It was observed that upon green-light illumination, the characteristic absorption of bR, with a maximum at ∼560 nm disappeared and a maximum at ∼410 nm appeared, indicating the formation of the M intermediate.