TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Photovoltaic Device: The oriented bacteriorhodopsin protein comprises a mutant bacteriorhodopsin protein. It also comprises a conservative amino acid substitution. The mutant bacteriorhodopsin protein comprises an amino acid substitution in an intrahelical loop, at a C terminus, or at an N terminus of a native bacteriorhodopsin protein. The substrate comprises gold, indium tin oxide, platinum on carbon, and/or meshed carbon nanotubes. The device comprises an anode and a cathode, where the anode comprises gold and the cathode comprises platinum. Preferred Method: In making the protein-based photovoltaic device, the oriented bacteriorhodopsin protein is deposited on the substrate by electrodeposition or by electrostatic layer-by-layer placement. Generating energy from sunlight further comprises exposing the photovoltaic cell to water, where the bacteriorhodopsin protein splits the water to produce hydrogen and oxygen gas, and where the hydrogen gas is collected and provides an energy source. It further comprises exposing the photovoltaic cell to brine, where the bacteriorhodopsin protein splits the brine to produce hydrogen and chlorine gas, and where the hydrogen gas is collected and provides an energy source. Preferred Mutant Bacteriorhodopsin Protein: The substituted amino acid is an amino acid naturally incorporated during translation. It is also a post-translationally modified amino acid. The substituted amino acid comprises a conservative substitution. The mutant bacteriorhodopsin protein binds covalently to a metal substrate, where the metal substrate comprises platinum, gold or a gold-coated nanotube. A second mutant bacteriorhodopsin protein is bound to the metal substrate, and where both proteins orient in the same direction on the substrate. Two amino acids in the native bacteriorhodopsin protein are replaced with two substituted amino acids that are different from that of native bacteriorhodopsin protein. The substituted amino acid comprises a cysteine, where the cysteine bonds covalently to a metal surface. The dipole moment of the mutant bacteriorhodopsin protein is greater than the dipole moment of the native bacteriorhodopsin protein. At least one amino acid in an extracellular intrahelical loop is replaced with a neutral or positively charged amino acid, and where at least one amino acid in an intracellular intrahelical loop is replaced with a neutral or negatively charged amino acid. The amino acid in the native bacteriorhodopsin protein is charged, and where the substituted amino acid is neutral or has a charge opposite to that of the amino acid in the native bacteriorhodopsin protein. The amino acid in the native bacteriorhodopsin protein is neutral, and where the substituted amino acid is charged, or where the substituted amino acid is acidic or basic. The amino acid in the native bacteriorhodopsin protein is acidic, and where the substituted amino acid is neutral or basic. Alternatively, the amino acid in the native bacteriorhodopsin protein is basic, and where the substituted amino acid is neutral or acidic. The substituted amino acid comprises a cysteine, and where the mutant bacteriorhodopsin protein has a dipole moment that is greater than the dipole moment of the native bacteriorhodopsin protein. EXAMPLE - No example given.