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Radical pair-based magnetic sensing in migratory birds

Periodic Reporting for period 1 - QuantumBirds (Radical pair-based magnetic sensing in migratory birds)

Reporting period: 2019-04-01 to 2020-09-30

The navigational abilities of night-migratory songbirds, travelling alone over thousands of kilometres, are absolutely staggering. The successful completion of these magnificent voyages depends crucially on the birds’ ability to sense the Earth’s magnetic field. Exactly how this magnetic sense works is one of the most significant open questions in biology and biophysics. The experimental evidence suggests something extraordinary. The birds’ magnetic compass sensor seems to rely on coherent quantum phenomena that indirectly allow astonishingly weak magnetic interactions to be detected in biological tissue. QuantumBirds brings together quantum physics, spin chemistry, behavioural biology, biochemistry, and molecular biology in an ambitious, imaginative and synergetic research programme that will prove whether the primary magnetic detection event occurring in the birds’ retinas involves the quantum spin dynamics of photochemically formed radical pairs in cryptochrome (Cry) proteins.

We are addressing three specific questions:

1. Are avian cryptochromes capable of functioning as magnetic compass receptors?
2. Do retinal neurons encode light-dependent, cryptochrome-derived magnetic information?
3. Are cryptochromes the primary magnetoreceptor molecules for magnetic compass orientation?

Success in this endeavour will: (a) revolutionise our understanding of magnetoreception, the least understood of all biological senses; (b) firmly establish the emerging field of “Quantum Biology” and thereby reduce by six orders of magnitude the threshold for sensory detection of weak stimuli in biological systems; (c) prepare the ground for the development of a novel and powerful range of bio-inspired magnetic sensing devices; and (d) provide insights that could be applied in quantum computing and guide research into the potential effects of weak anthropogenic electromagnetic fields on human health.
Results from the first 18 months of the project have been published in 9 articles in the scientific literature. The main findings can be summarised as follows.

1. The crystal structure of pigeon Cry4 has been determined.

2. Behavioural experiments suggest that the spin coherence lifetime of the magnetically sensitive radical pair in Eurasian blackcaps is in the range 2-10 microseconds.

3. Spin dynamics simulations have shown that the operation of a radical pair magnetoreceptor cannot be satisfactorily be described without an exact quantum mechanical treatment and is therefore deserving of a place in “Quantum Biology”.

4. Six proteins have been identified as having interactions with robin Cry4 that could play a role in the magnetic signal transduction pathway.

5. Spin dynamics simulations have identified the highly restrictive conditions under which a flavin-superoxide radical pair could form the basis of a geomagnetic compass sensor.

6. A novel isoform of robin Cry4 has been identified; its circadian expression patterns suggest that it has a different function to the previously described form of robin Cry4.

7. Recruitment data from seabird colonies in the UK correlate with the natural drift in the geomagnetic field and thus indicate that these birds use a magnetic map.
1. An Information Theory approach has been developed to assess the performance of Cry-based radical pairs under the low light levels experienced by nocturnal migrants.

2. Confocal fluorescence microscopy techniques have been developed for the investigation of magnetic field effects on radical pair reactions in cryptochromes.

We are on track to answer the three questions mentioned above.