Page 8 - PERIODIC Magazine Issue 7

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
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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, (doi.org/10.1002/anie.201814370). Narayan, A.; Enzymes
trapped and zapped for use outside cells, Nature 2019, 567, 317-318, (doi: 10.1038/
d41586-019-00761-2).
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Periodic The Magazine of the Department of Chemistry