Solvent driving force ensures fast formation of a persistent and well-separated radical pair in plant cryptochrome

Gesa Lüdemann, Ilia A. Solov'yov, Tomás Kubar, Marcus Elstner
Journal of the American Chemical Society
The photoreceptor protein cryptochrome is thought to host, upon light absorption, a radical pair which issensitive to very weak magnetic fields, endowing migratory birds with a magnetic compass sense. The molecular mechanism which
leads to formation of a stabilised, magnetic field sensitive radical pair has despite various theoretical and experimental
efforts not been unambiguously identified yet. We challenge this unambiguity through a unique quantum mechanical molecular
dynamics approach where we perform electron transfer dynamics simulations taking into account the motion of the protein upon
the electron transfer. This approach allows us to follow the time evolution of the electron transfer in an unbiased fashion
and to reveal the molecular driving force which ensures fast electron transfer in cryptochrome guaranteeing formation of a persistent
radical pair suitable for magnetoreception. We argue that this unraveled molecular mechanism is a general principle inherent
to all proteins of the cryptochrome/photolyase family and that cryptochromes are, therefore, tailored to potentially function as
efficient chemical magnetoreceptors.