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. LH 1 has previously been observed to have superior photostability over LH 2 (Magis et al.  Biochim. Biophys. Acta, 1798, 637-645); this characteristic is maintained even with the introduction of Cys residues. The integral membrane protein light-harvesting complex 2 of Rhodobacter sphaeroides has been engineered to express cysteine residues on either the cytoplasmic or periplasmic face of the complex. These cysteine residues permit the oriented attachment of the isolated complexes on a gold surface. The complexes are not denatured by this simple attachment procedure as demonstrated by fluorescence emission spectroscopy. © 2011 The Authors.