title: Carbon Dots as Versatile Photosensitizers for Solar-Driven Catalysis with Redox Enzymes.
abstract: Light-driven enzymatic catalysis is enabled by the productive coupling of a protein to a photosensitizer. Photosensitizers used in such hybrid systems are typically costly, toxic, and/or fragile, with limited chemical versatility. Carbon dots (CDs) are low-cost, nanosized light-harvesters that are attractive photosensitizers for biological systems as they are water-soluble, photostable, nontoxic, and their surface chemistry can be easily modified. We demonstrate here that CDs act as excellent light-absorbers in two semibiological photosynthetic systems utilizing either a fumarate reductase (FccA) for the solar-driven hydrogenation of fumarate to succinate or a hydrogenase (H2ase) for reduction of protons to H2. The tunable surface chemistry of the CDs was exploited to synthesize positively charged ammonium-terminated CDs (CD-NHMe2+), which were capable of transferring photoexcited electrons directly to the negatively charged enzymes with high efficiency and stability. Enzyme-based turnover numbers of 6000 mol succinate (mol FccA)-1and 43,000 mol H2(mol H2ase)-1were reached after 24 h. Negatively charged carboxylate-terminated CDs (CD-CO2-) displayed little or no activity, and the electrostatic interactions at the CD-enzyme interface were determined to be essential to the high photocatalytic activity observed with CD-NHMe2+. The modular surface chemistry of CDs together with their photostability and aqueous solubility make CDs versatile photosensitizers for redox enzymes with great scope for their utilization in photobiocatalysis.
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Georgina A M
authors.initials: GA
authors.lastname: Hutton
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Reuillard
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Benjamin C M
authors.initials: BC
authors.lastname: Martindale
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Caputo
authors.affiliation: School of Chemistry and School of Biological Sciences, University of East Anglia , Norwich Research Park, Norwich NR4 7TJ, U.K.
authors.forename: Colin W J
authors.initials: CW
authors.lastname: Lockwood
authors.affiliation: School of Chemistry and School of Biological Sciences, University of East Anglia , Norwich Research Park, Norwich NR4 7TJ, U.K.
authors.forename: Julea N
authors.identifier: 0000-0002-9624-5226
authors.initials: JN
authors.lastname: Butt
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Erwin
authors.identifier: 0000-0002-7781-1616
authors.initials: E
authors.lastname: Reisner
mesh_terms: D055162:Biocatalysis; D002244:Carbon / Q000737:chemistry*; D046969:Clostridium acetobutylicum / Q000201:enzymology; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D053758:Nanoparticles; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry*; D011487:Protein Conformation; D020592:Shewanella / Q000201:enzymology; D013385:Succinate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D013472:Sunlight
chemical_list: D017319:Photosensitizing Agents; D002244:Carbon; D006864:Hydrogenase; D013385:Succinate Dehydrogenase