Cobalamin Catalytic Centers for Stable Fuels Generation from Carbon Dioxide

Our aim is to design and construct protein-based artificial photosynthetic systems that reduce carbon dioxide (CO$_{2})$ to stable fuel forms within the robust and adaptable ($\beta \alpha )_{8}$ TIM-barrel protein structure. The EutB subunit of the adenosylcobalamin-dependent enzyme, ethanolamine ammonia-lyase, from \textit{Salmonella typhimurium}, was selected as the protein template. This system was selected because the Co$^{I}$ forms of the native cobalamin (Cbl) cofactor, and the related cobinamide (Cbi), possess redox properties that are commensurate with reduction of CO$_{2}$. The kinetics of photo- (excited 5'-deazariboflavin electron donor) and chemical [Ti(III)] reduction, and subsequent reaction, of the Cbl and Cbi with CO$_{2}$ are measured by time-resolved UV/visible absorption spectroscopy. Products are quantified by NMR spectroscopy. The results address the efficacy of the organocobalt catalytic centers for CO$_{2}$ reduction to stable fuels, towards protein device integration.