Magnetically sensitive chemical reactions – how birds find their wayaround.

P. J. Hore

Department of Chemistry, University of Oxford, UK

Migratory birds travel spectacular distances each year, navigating and orienting by a variety of means, most of which are poorly understood. Among them is a remarkable ability to perceive the intensity and direction of the Earth’s magnetic field. Biologically credible mechanisms for the sensing of such weak fields are scarce and in recent years just two proposals have emerged as frontrunners. One, essentially classical, involves clusters of iron-containing particles. The other relies on the magnetic sensitivity of short-lived photochemical intermediates called radical pairs. The lattermodel began to attract interest following the proposal that the necessary photochemistry (the avian magnetic compass is light-dependent) could take place in the bird’s retina in specialised photoactive proteins called cryptochromes. The coherent dynamics of the electron-nuclear spin systems of pairs of organic radicals is conjectured to lead to changes in the yields of reaction products even though the interaction with the geomagnetic field is many orders of magnitude smaller than the thermal energy per molecule.

I will outline the basis of the radical pair mechanism, explain how extremely weak magnetic interactions can affect the outcome of chemical transformations, present some of the experimental evidence for the cryptochrome hypothesis, and comment on the extent to which cryptochromes are fit-for-purpose as magnetoreceptors.

时间：8月29号，周五下午2：30

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