Radical pairs can explain magnetic field and lithium effects on the circadian clock

Abstract

Drosophila's circadian clock can be perturbed by magnetic fields, as well as by lithium administration. Cryptochromes are critical for the circadian clock. Further, the radical pairs in cryptochrome also can explain magnetoreception in animals. Based on a simple radical pair mechanism model of the animal magnetic compass, we show that both magnetic fields and lithium can influence the spin dynamics of the naturally occurring radical pairs and hence modulate the circadian clock's rhythms. Using a simple chemical oscillator model for the circadian clock, we show that the spin dynamics influence a rate in the chemical oscillator model, which translates into a change in the circadian period. Our model can reproduce the results of two independent experiments, magnetic fields and lithium effects on the circadian clock. Our model predicts that stronger magnetic fields would shorten the clock's period. We also predict that lithium influences the clock in an isotope-dependent manner. Furthermore, our model also predicts that magnetic fields and hyperfine interactions modulate oxidative stress. The findings of this work suggest that quantum nature and entanglement of radical pairs might play roles in the brain, as another piece of evidence in addition to recent results on xenon anesthesia and lithium effects on hyperactivity.

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“…level in rat pulmonary atrial muscle cells and human umbilical vein endothelial cells under the effect oscillating magnetic field [53][54]. More recently, Zadeh-Haghighi has also suggested a similar scheme for magnetic field effect on planarian regeneration where they mentioned Complex I of ETC as the possible site of superoxide-flavin radical pair formation [55]. However, superoxide has exceedingly fast spin relaxation of superoxide due its symmetry (few nanoseconds [56]) which cause the coherent time of such a radical pair to be few orders shorter than the required effective time for magnetic fields in their suggested models.…”