Next Generation Designed Protein as a Photosensitizer for Biophotovoltaics Prepared by Expanding the Genetic Code

We explored the possibility of generating nonpoisonous, renewable, low cost and a completely biodegradable photosensitizer for dye-sensitized solar cells (DSSC) as an alternative to synthetic molecules that involve expensive, time-consuming tedious synthesis and purification procedures. Several natural dyes from plants and microbes had successfully been demonstrated as photosensitizers to develop biosensitized solar cells (BSSCs). The objective of this work is to develop a next generation cleaner sensitizer for BSSC using a green fluorescent protein (GFP) and its designer variant (GFPdopa) through an expanding genetic code approach. The designer protein showed higher adsorption with TiO₂ surface through oriented immobilization. The nanostructured layer formed by GFPdopa with TiO₂ resulted in 0.94% level of photon conversion efficiency with open circuit voltage of 0.60 V, short circuit current of 1.75 mA/cm² and fill factor of 0.88. It is one of the better energy conversion efficiencies obtained for BSSC when compared to with earlier reported sensitizers generated through protein and chemical complex synergism. From the results obtained, it is suggested that designer fluorescent itself can generate similar photoconversion efficiency and also could serve as an environmental friendly photosensitizer. The research and efficiency level of BSSC is in the early stages, and our proof of principle opens a new avenue to synthesize biologically designer sensitizers for BSSC. It also could be widely applied to other proteins to develop efficient sensitizers for BSSC with a green approach

Bioconjugation of L-3,4-Dihydroxyphenylalanine Containing Protein with a Polysaccharide

We describe the simple bioconjugation strategy in combination of periodate chemistry and unnatural amino acid incorporation. The residue specific incorporation of 3,4-dihydroxy-L-phenylalanine can alter the properties of protein to conjugate into the polymers. The homogeneously modified protein will yield quinone residues that are covalently conjugated to nucleophilic groups of the amino polysaccharide. This novel approach holds great promise for widespread use to prepare protein conjugates and synthetic biology applications.X112625sciescopu