Two-Dimensional Molecular Assembly of Bacteriochlorophyll a Derivatives Using Synthetic Poly(ethylene glycol)-Linked Light-Harvesting Model Polypeptides on a Gold Electrode Modified with Supported Lipid Bilayers.

Abstract

The two-dimensional molecular assembly was accomplished of bacteriochlorophyll a (BChl a) and zinc-substituted BChl a (Zn-BChl a) together with synthetic poly(ethylene glycol)(PEG)-linked light-harvesting (LH) model polypeptides on a gold Au(111) electrode modified with supported lipid bilayers. Model polypeptides for LH1-α from Rhodospirillum (Rs.) rubrum were successfully synthesized and stably assembled with Zn-BChl a in 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1'-glycerol)] (DOPG) lipid bilayers on an electrode at room temperature, as well as in liposomal solution, in which the Zn-BChl a complex unlike BChl a, was stably assembled. The PEG moiety of the model polypeptide assisted the stable assembly with an α-helical conformation of the LH1-α model peptides together with these pigments onto the gold electrode with defined orientation. The photocurrent response depended on the combinations of the pigments and synthetic LH model polypeptides. The results presented herein will be useful for the self-assembly of these complexes on electrodes to construct efficient energy-transfer and electron-transfer reactions between individual pigments in lipid bilayers.