The Radical-Pair Mechanism of Magnetoreception

Annu Rev Biophys. 2016 Jul 5;45:299-344. doi: 10.1146/annurev-biophys-032116-094545. Epub 2016 May 16.


Although it has been known for almost half a century that migratory birds can detect the direction of the Earth's magnetic field, the primary sensory mechanism behind this remarkable feat is still unclear. The leading hypothesis centers on radical pairs-magnetically sensitive chemical intermediates formed by photoexcitation of cryptochrome proteins in the retina. Our primary aim here is to explain the chemical and physical aspects of the radical-pair mechanism to biologists and the biological and chemical aspects to physicists. In doing so, we review the current state of knowledge on magnetoreception mechanisms. We dare to hope that this tutorial will stimulate new interdisciplinary experimental and theoretical work that will shed much-needed additional light on this fascinating problem in sensory biology.

Keywords: cryptochrome; magnetic compass; magnetic-field effects; migratory birds; retina; spin chemistry.

Publication types

  • Review

MeSH terms

  • Animal Migration
  • Animals
  • Birds / physiology
  • Cryptochromes / metabolism*
  • Free Radicals / metabolism
  • Magnetic Fields*
  • Retina / metabolism
  • Space Perception


  • Cryptochromes
  • Free Radicals