Developing a Biologically-Inspired Molecular Solar Energy Conversion Device: Reaction of Solution and Protein-Bound Cobalamins with Carbon Dioxide and Halo-Organic Compounds

Our aim is to design and construct protein-based artificial photosynthetic systems that reduce carbon dioxide (CO$_{2})$ and toxic halo-organic compounds within the robust and adaptable ($\beta \alpha )_{8}$ TIM-barrel protein structure. The EutB subunit of the adenosylcobalamin-dependent enzyme, ethanolamine ammonia-lyase (EAL), from \textit{Salmonella typhimurium}, was selected as the protein template. The Co$^{I}$ forms of the native cobalamin (Cbl) cofactor and a derivative, cobinamide (Cbi), possess relatively low redox potentials that are commensurate with reduction of CO$_{2}$ and halo-organic compounds. Titanium$^{III}$ citrate and pulsed laser-excited 5'-deazariboflavin (5'-DRF) were used to reduce Cbl or Cbi. UV/visible absorption spectroscopy was used to monitor the reaction kinetics of reduced Cbl and Cbi with CO$_{2}$ and halo-organics, and 13C-NMR was used for product analysis. The results provide fundamental information for development of an organocobalt-based protein-catalytic device for stable fuels generation and toxic chemical remediation.