Alternate, sustainable energy sources are gaining increased attention from chemists, physicists and engineers, as mankind realizes the limited availability and adverse environmental impacts of burning fossil fuels. Solar cells have great potential to be used as a sustainable and green energy source for the future. In this regard a prototype of a nano solar cell containing the Mycobacterial channel protein MspA, as the matrix for vectorial electron transport has been successfully achieved.
MspA is an octameric trans-membrane channel protein (i.e. porin) produced by Mycobacterium smegmatis and is one of the most stable porins known so far. Wild type MspA has been successfully isolated, analyzed and purified to obtain crystals. A novel Ruthenium-phenanthroline-viologen-maleimide dye which is a fast vectorial electron transporter, has been synthesized, purified and successfully bound to the terminal end of wild type MspA, via the cysteine-maleimide bond. The dye-protein complex has then been adsorbed onto TiO2 plates and subjected to incident sunlight. The protein appeared to be stable under the incident wavelength and a steady current is observed. A 1% incident photon conversion efficiency of sunlight into current by the MspA-dye complex has been achieved so far. This finding marks the first ever evidence of a ‘protein nano solar cell’. Future developments to enhance the efficiency of the system are proposed.