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Armstrong Group

          The team working on nanoconfined enzymes.  L-R:  Prof. Fraser Armstrong, Dr. Clare Megarity, Dr. Bhavin Siritanaratkul, Giorgio Morello, Lei Wan, Beichen Cheng

              “Electrocatalytic                               a new system for efficient organic synthesis which
              volleyball” with                                could be monitored and controlled throughout hours/
                                                              days of activity. Both enzymes are confined at very high
              nanoconfined enzymes                            local concentrations in the network of nanocavities and
                                                              diffusion distances are tiny, hence the overall rate of
              Think of our Chemistry Department: the offices,   reaction (reactant to product) is massively amplified. The
              laboratories, instruments and stores are clustered within   resulting material denoted (FNR+E2)@ITO/support is
              a five minute walk down South Parks Road. It is not hard   capable of performing any number of complex organic
              to understand why this arrangement is more efficient   reactions simply by varying E2, E3, E4, etc, or the
              and effective than spreading the facilities across the city   electrode potential to drive oxidation or reduction. The
              of Oxford. Likewise, confinement and ordering of tasks,   electrode is connected to a power source and placed in
              as in a production line, is an essential strategy adopted   the reactant solution
              by nature. Drawing inspiration from mitochondria and   To date, six Part II students have worked on the project
              chloroplasts, the Armstrong group is applying multi-  and currently three DPhil students, Giorgio Morello, Lei
              task confinement at the nanoscale to enhance whole   Wan and Beichen Cheng are expanding the repertoire
              sequences of enzyme reactions (cascades) in tiny   by driving the system with light, using it in a fuel cell
              energizable pores.                              configuration, scaling up for industrial use, and other
              In plants, ferredoxin NADP  reductase (FNR) is the   novel applications. The group is already developing
              pivotal enzyme of biosynthesis; it converts electrons   complex cascades through careful selection of E2, E3,
              derived from light-harvesting complexes into “hydrogen”   E4,… and control of the electrode potential, creating
              trapped in the nicotinamide cofactor, NADPH. NADPH   new opportunities for synthesis and diagnostics. “It’s
              may be considered biology’s sodium borohydride and   exciting because these discoveries open up so many
              is used by numerous other enzymes for downstream   facets to explore,” Dr. Megarity explains. The academic
              synthesis, including CO  fixation.              community seems to agree - the research, published in
                                                              Angewandte Chemie, was also highlighted in Nature!
              Postdoctoral researchers, Drs. Clare F. Megarity and
              Bhavin Siritanaratkul, and Part II student, Thomas
              Roberts, established that FNR binds tightly in the vast
              porous network of an indium tin oxide (ITO) electrode
              formed by electrodeposition of ITO nanoparticles on a
              support such as titanium. In this trapped state, FNR is
              highly active and stable, and electron transfers are very
              fast. It is hypothesised that the positively charged surface
              of FNR is attracted to the negatively charged surface of
              ITO nanoparticles. The cavities formed by the packing
              of the ITO nanoparticles have diameters ranging from
              5-100 nm, which is similar to the main compartment of
              chloroplasts. The system developed in the Armstrong
              group thus exploits the ITO electrode as an alternative   A schematic diagram showing enzymatic cascades in the ITO nanopores, which can be
                                                               continuously monitored via current measurements.
              source (or sink) of electrons for FNR. By introducing a   References: Megarity, C.F.; Siritanaratkul, B.; et. al.; Electrocatalytic volleyball: rapid
              second enzyme, E2, that uses NADP(H) into the same   nanoconfined nicotinamide cycling for organic synthesis in electrode pores, Angew. Chem.
              ITO pores, Drs. Megarity and Siritanaratkul established   Int. Ed. 2019, 58, 4948-4952, ( Narayan, A.; Enzymes
                                                              trapped and zapped for use outside cells, Nature 2019, 567, 317-318, (doi: 10.1038/
            Periodic        The Magazine of the Department of Chemistry
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