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N ew Research continued N ew Research continued

Benesch Group Timmel Group

Unravelling protein origins Imaging magnetic field effects

A collaborative study between the Timmel, Aarts, and
The Benesch group, working alongside researchers from they found that just two changes to the structure of
the Universities of Chicago, Nebraska, and Texas A&M, an ancestral protein led to both the formation of the Mackenzie groups has demonstrated for the first time
have demonstrated that the structures responsible for four-part complex and the optimisation of its oxygen- the use of confocal microscopy to investigate the
specialised functions of complex proteins can come binding ability. magnetic field sensitivity of chemical reactions.
about via surprisingly simple mechanisms.
A traditional view of evolution says that complexity in Confocal microscopy is an optical imaging technique
The evolution of proteins that perform all the nature comes about through many successive small that blocks out-of-focus light, allowing a thin
specialised functions in our bodies is one of the biggest mutations with gradual improvements in function – plane containing the fluorophore of interest to be
puzzles in biology. Haemoglobin – responsible for this study showed that, on a molecular level, a couple distinguished from that of the surroundings.
oxygen transport in blood – is made of four protein of simple mutations sometimes lead very quickly to
sub-units that form the vital oxygen-carrying complex. complex behaviour. The technique was used to observe magnetic field
effects (MFEs) both in solution and in single crystals.
The systems were irradiated to form excited states
In the collaborative study, published in Nature, the Reference: Pillai, A. S. et al., Nature 581 (2020) 480–485
researchers identified the “missing link” that explains (doi.org/10.1038/s41586-020-2292-y). that can quickly undergo electron transfer to produce
how haemoglobin’s remarkable oxygen-transport radicals: chemical species containing unpaired electrons.
abilities evolved. By reconstructing ancient proteins, The excited state can also fluoresce to reform the initial
state, and it is this fluorescence that is observed using
confocal microscopy. Variation in percentage magnetic field effect (MFE) in a
flavin-doped lysozyme crystal in synchrony with magnetic field
The collaborative study traced the How does a magnetic field affect this process? The steps between 0 mT (red) and 16 mT (blue).
evolutionary roots of haemoglobin’s radicals formed carry an unpaired electron (have non-
structure and function. zero spin) which is associated with a non-zero magnetic

moment. This magnetic moment in turn interacts with differences in response when the field was applied
an applied magnetic field. The direction and intensity parallel or perpendicular to a single crystal of tetracene,
of this field can affect the products formed from these a molecular organic semiconductor.
radical states, and thereby affect the fluorescence An exciting application of this work will be to test the
intensity for the photochemical cycle.
directional magnetic sensitivity of immobilised samples
In the team’s experiments a weak magnetic field was of cryptochrome, a blue-light sensitive protein that is
repeatedly switched on or off, and step changes in the thought to be crucial in the mechanism by which birds
intensity of fluorescence were observed at coincident detect the direction of the Earth’s magnetic field when
times, providing clear evidence for the magnetic field they migrate.
sensitivity of the reaction in the imaged solution or Victoire Déjean, DPhil student in the Timmel group,
crystal. The main aim of the work was to explore the said that “this paper is the first big achievement of a
potential of confocal microscopy to investigate spatially fantastic collaboration between three research groups.
resolved MFEs, with possible applications including I am very excited about the new avenues of research
investigating the effects of magnetic fields on light- it opens up, especially regarding our goal to show that
induced processes in living tissues or in synthetic cryptochromes, the blue light photosensitive proteins
materials and devices.
found in birds’ retinae, can act as chemical compasses.”
As well as viewing the effect of the magnetic field Reference: Déjean, V. et al., Chemical Science 11 (2020)
on diffusing flavin molecules in a single crystal of a 7772–7781 (doi.org/10.1039/D0SC01986K).
small protein, they were able to observe directional

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