Use of engineered unique cysteine residues to facilitate oriented coupling of proteins directly to a gold substrate.

A prerequisite for any "lab on a chip" device that utilizes an electrical signal from the sensor protein is the ability to attach the protein in a specific orientation onto a conducting substrate. Here, we demonstrate the covalent attachment to a gold surface of light-harvesting membrane proteins, from Rhodobacter sphaeroides, via cysteine (Cys) residues engineered on either the cytoplasmic or periplasmic face. This simple directed attachment is superior in its ability to retain light-harvesting complex (LHC) function, when compared to a similar attachment procedure utilizing a self-assembled monolayer on gold.

Light harvesting, energy transfer and electron cycling of a native photosynthetic membrane adsorbed onto a gold surface.

Photosynthetic membranes comprise a network of light harvesting and reaction center pigment-protein complexes responsible for the primary photoconversion reactions: light absorption, energy transfer and electron cycling. The structural organization of membranes of the purple bacterial species Rb. sphaeroides has been elucidated in most detail by means of polarized light spectroscopy and atomic force microscopy.