Ilia Solov'yov, Tatiana Domratcheva, and Klaus Schulten.
Separation of photo-induced radical pair in cryptochrome to a
functionally critical distance.
Scientific Reports, 4:3845, 2014.
(8 pages).
(PMC: PMC4894384)
SOLO2014
Animals and plants, together with other life forms, possess internal clocks that attune
them to the daily rhythm on Earth. A key blue-light receptor serving for this purpose is a
protein called cryptochrome. An apparent second role of cryptochrome is that of a sensor
for the Earth's magnetic field, which helps migratory birds in long-range navigation. The
latter function of cryptochrome arises from a light-induced reduction of its flavin cofactor
through step-wise electron transfer involving several tryptophan amino acid residues.
Here, this electron transfer is investigated by combining quantum-chemical and classical
molecular dynamics calculations. The results reveal that the transfer occurs in tandem with
key rearrangements in the cryptochrome structure in the vicinity of the polar environment
of the protein's tryptophan residues and that a second transfer step can extend electron -
- hole separation before the state reached in a first transfer step becomes stabilized
through proton transfer. A large electron-hole separation extends the life time of the
reduced state of cryptochrome's flavin cofactor and, thereby, extends receptor signaling as
well as increases the signaling's sensitivity to the geomagnetic field.
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