Fabrication of oriented poly-L-lysine/bacteriorhodopsin-embedded purple membrane multilayer structure for enhanced...

A poly-L-lysine (PLL)/bacteriorhodopsin-embedded purple membrane (bR-PM) multilayer film has been successfully constructed by a layer-by-layer (LbL) assembly process to enhance the photoelectric response of bR. The assembly conditions were investigated and optimized. The PLL/bR-PM adsorption process was in situ studied by surface plasmon resonance and the growth of multilayer was further characterized by UV-vis absorption spectroscopy. The results indicate that the amount of adsorbed bR-PM vs. the assembled layer number exhibits linear relationship. The atomic force microscopy images of sequentially assembled PLL/bR-PM bilayers show that the patch structure of bR-PM in the structure is well preserved and the roughness increases with increase of the bilayer number. The peak photocurrent generated from PLL/bR-PM film increases with increase of the PLL/bR-PM bilayers until achieving a maximum value. The photocurrent of bR-PM from the film through PLL assembler is higher than those assembled by other polycations, thus rendering a new platform to effectively enhance the bR photoelectric responses.