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ChemNav Report Summary

Project ID: 340451
Funded under: FP7-IDEAS-ERC
Country: United Kingdom

Mid-Term Report Summary - CHEMNAV (Magnetic sensing by molecules, birds, and devices)

In 2007 a female bar-tailed godwit – a medium sized wading bird – was tracked by satellite flying non-stop from Alaska to New Zealand, an 8-day non-stop trip of more than 11,000 km across the Pacific Ocean. Countless godwits cover similar migratory routes in both directions every year. Annually, billions of birds fly thousands of kilometres between wintering and breeding grounds over distances only slightly less awesome. One of the many questions raised by these spectacular migrations is how birds manage to navigate over such large distances. Amongst a number of directional cues – the sun, stars, odours, landmarks – it is clear that birds use the Earth’s magnetic field to orient themselves. ChemNav aims to elucidate the biophysical mechanism of avian magnetoreception, to understand the practical requirements for efficient chemical sensing of magnetic fields, and to explore the potential for bio-inspired magnetic sensing devices. These goals are being approached in four directions.

(1) The required magnetically sensitive chemistry is believed to take place in photoreceptor proteins called cryptochromes in the retina. There are now strong indications that cryptochromes are fit for this purpose, but we need to know much more about the details of their operation as biological compasses. We are approaching this by developing new, sensitive forms of spectroscopy that allow the magnetic responses of these proteins to be determined under a wide variety of experimental conditions. An important discovery has been an unanticipated chemical amplification mechanism with the potential to boost the magnitude of the primary directional information delivered by a cryptochrome sensor. There appears to be ample scope for this mechanism to have been evolutionarily optimised and we see no reason why Nature would not have exploited it to afford birds a more precise compass bearing.

(2) Versatile magnetic sensor systems are being constructed using the concept of non-natural protein ‘maquettes’. These new model systems have the structural, kinetic and magnetic flexibility to allow the practical requirements for efficient chemical magnetic sensing to be tested, compared and optimised. Inspired by cryptochromes, but with no sequence similarity to the natural proteins, maquettes are being produced in Philadelphia and characterized spectroscopically and magnetically in Oxford. The maquettes are being refined by progressive, directed, iterative sequence changes to uncover and understand the practical design and engineering rules for optimum magnetic sensitivity.

(3) We are developing the theory of chemical magnetoreception to allow more efficient and reliable interpretation of experimental data, to guide the design of effective sensors, and to test aspects of the mechanism and new ideas that are currently too challenging for experimental study. One particularly interesting idea that has emerged in the last few months is the possibility that the precision of the compass bearing available from a cryptochrome may be much higher than hitherto supposed. The condition for the existence of this enhancement is that certain molecular motions within the protein must be of low amplitude and high frequency. To explore this possibility, molecular dynamics simulations have been performed to give the motional data necessary for realistic modelling of the magnetic responses of the cryptochromes.

(4) Finally, the lessons learnt from these studies will be used to explore the potential for bio-inspired, organic semiconductor-based, magnetic sensors. It is not too unrealistic to imagine, in say 10 years’ time, cheap, accurate, nanometre-scale magnetic sensing devices with microsecond time resolution and microtesla sensitivity. As a first step in this direction we are measuring the magnetic sensitivity of a variety of organic molecules that are being synthesized by groups in China as potential materials for efficient organic light-emitting diodes.

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United Kingdom
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