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

TL;DR

This paper proposes a radical pair mechanism model to explain how magnetic fields and lithium influence the circadian clock in Drosophila, suggesting quantum effects in biological timing and stress regulation.

Contribution

It introduces a simple radical pair-based model that accounts for magnetic and lithium effects on circadian rhythms, aligning with experimental observations.

Findings

Magnetic fields and lithium affect radical pair spin dynamics, altering circadian periods.

The model predicts stronger magnetic fields shorten the circadian period.

Lithium's effects are isotope-dependent and influence oxidative stress.

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.