Fabrication of a Retinal-protein Photoreceptor Array

A pixel-architecture film of retinal proteins was prepared by an approach combining chemical, physical and biological technologies. Oriented multilayers of purple membrane composed of bacteriorhodopsin (BR) and lipids were patterned on an array of gold electrode pixels. In order to improve stability and resolution, the gene engineering technique was employed to make a mutant of the protein BR by replacing the 36^th amino acid residue from aspartic acid to cysteine with a thiol end group ready to react with gold; electric sedimentation was used to guarantee the high probability of formation of the Au-S bond and meanwhile to orient BR; further chemical crosslinking was introduced among layers of purple membranes to significantly enhance photoelectrical signals while keeping high stability. The non-bound BR region was eventually washed out by detergent, and the remaining BR pixels were thus detergent resistant due to chemical crosslinking among BR layers and covalent binding between the multilayer and the substrate. The protein array was confirmed to keep photoelectrical activity.