Approximately 50 species, including birds, mammals, reptiles, amphibians, fish, crustaceans and insects, are known to use the Earth’s magnetic field for orientation and navigation1. Birds in particular have been intensively studied, but the biophysical mechanisms that underlie the avian magnetic compass are still poorly understood. One proposal, based on magnetically sensitive free radical reactions2,3, is gaining support4,5,6,7,8,9,10,11 despite the fact that no chemical reaction in vitro has been shown to respond to magnetic fields as weak as the Earth’s (∼50 μT) or to be sensitive to the direction of such a field. Here we use spectroscopic observation of a carotenoid–porphyrin–fullerene model system to demonstrate that the lifetime of a photochemically formed radical pair is changed by application of ≤50 μT magnetic fields, and to measure the anisotropic chemical response that is essential for its operation as a chemical compass sensor. These experiments establish the feasibility of chemical magnetoreception and give insight into the structural and dynamic design features required for optimal detection of the direction of the Earth’s magnetic field.
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We thank M. Ahmad, D. Carbonera, M. di Valentin, G. Giacometti, C. W. M. Kay, P. Raynes, T. Ritz and R. Wiltschko for discussions; N. Baker for technical assistance; and the Oxford Supercomputing Centre for allocation of CPU time. P.J.H., C.R.T. and co-workers are funded by the Engineering and Physical Sciences Research Council, the Human Frontier Science Program, the EMF Biological Research Trust and the Royal Society. D.G. and co-workers are funded by the US National Science Foundation. I.K. is a Fellow by Examination at Magdalen College, Oxford.
Author Contributions K.M., K.B.H. and F.C. performed the experiments. K.M., K.B.H. and C.R.T analysed the data. P.A.L. and D.G. synthesized the triad molecule. C.T.R. and P.J.H. analysed the orientational averaging. I.K. performed ab initio calculations. F.C., C.R.T. and P.J.H. designed the study. C.R.T. co-ordinated the study. P.J.H. wrote the paper. All authors discussed the results and commented on the manuscript.
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Maeda, K., Henbest, K., Cintolesi, F. et al. Chemical compass model of avian magnetoreception. Nature 453, 387–390 (2008). https://doi.org/10.1038/nature06834
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