title: Magnetically sensitive light-induced reactions in cryptochrome are consistent with its proposed role as a magnetoreceptor.
abstract: Among the biological phenomena that fall within the emerging field of "quantum biology" is the suggestion that magnetically sensitive chemical reactions are responsible for the magnetic compass of migratory birds. It has been proposed that transient radical pairs are formed by photo-induced electron transfer reactions in cryptochrome proteins and that their coherent spin dynamics are influenced by the geomagnetic field leading to changes in the quantum yield of the signaling state of the protein. Despite a variety of supporting evidence, it is still not clear whether cryptochromes have the properties required to respond to magnetic interactions orders of magnitude weaker than the thermal energy, k(B)T. Here we demonstrate that the kinetics and quantum yields of photo-induced flavin-tryptophan radical pairs in cryptochrome are indeed magnetically sensitive. The mechanistic origin of the magnetic field effect is clarified, its dependence on the strength of the magnetic field measured, and the rates of relevant spin-dependent, spin-independent, and spin-decoherence processes determined. We argue that cryptochrome is fit for purpose as a chemical magnetoreceptor.
authors.affiliation: Department of Chemistry, University of Oxford, Centre for Advanced Electron Spin Resonance, Inorganic Chemistry Laboratory, Oxford OX1 3QR, United Kingdom.
authors.forename: Kiminori
authors.initials: K
authors.lastname: Maeda
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Robinson
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Henbest
authors.forename: Hannah J
authors.initials: HJ
authors.lastname: Hogben
authors.forename: Till
authors.initials: T
authors.lastname: Biskup
authors.forename: Margaret
authors.initials: M
authors.lastname: Ahmad
authors.forename: Erik
authors.initials: E
authors.lastname: Schleicher
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
authors.forename: Christiane R
authors.initials: CR
authors.lastname: Timmel
authors.forename: P J
authors.initials: PJ
authors.lastname: Hore
mesh_terms: D000042:Absorption; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D056931:Cryptochromes / Q000378:metabolism*; D004583:Electrons; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D007700:Kinetics; D008027:Light; D060526:Magnetic Fields; D008280:Magnetics; D010777:Photochemistry; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013057:Spectrum Analysis; D014364:Tryptophan / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D029968:Escherichia coli Proteins; D011956:Receptors, Cell Surface; D005182:Flavin-Adenine Dinucleotide; D014364:Tryptophan