# The sensitivity of a radical pair compass magnetoreceptor can be significantly amplified by radical scavengers

**Authors:** Daniel R. Kattnig, P. J. Hore  
**arXiv:** [1706.04564](https://arxiv.org/abs/1706.04564)  
**Date:** 2017-06-14  
**Summary page:** https://www.summarizepaper.com/en/paper/1706.04564v3/

## Key points

- Researchers proposed a new version of the current model for how birds obtain navigational information from the Earth's magnetic field.
- The primary detection mechanism of this compass sense involves the quantum spin dynamics of radical pairs formed transiently in cryptochrome proteins.
- The new model suggests that spin-selective recombination of the radical pair is not essential, and instead one of the two radicals reacts with a paramagnetic scavenger via spin-selective electron transfer.
- Through simulations, they showed that this new scheme offers greatly enhanced sensitivity to a 50 μT magnetic field and allows animal cryptochromes with a tetrad (rather than a triad) of tryptophan electron donors to still act as viable magnetic compass sensors.
- Lifting the restriction on the rate of spin-selective recombination reaction allows detrimental effects such as inter-radical exchange and dipolar interactions to be minimized by placing the radicals much further apart than in the current model.
- These findings hope to gain further insight into how birds navigate using their remarkable ability to detect magnetic fields.

## Summary

In a recent study, researchers Daniel R. Kattnig and P.J. Hore proposed a new version of the current model for how birds obtain navigational information from the Earth's magnetic field. The primary detection mechanism of this compass sense is uncertain but appears to involve the quantum spin dynamics of radical pairs formed transiently in cryptochrome proteins. The new model suggests that spin-selective recombination of the radical pair is not essential, and instead one of the two radicals reacts with a paramagnetic scavenger via spin-selective electron transfer. Through simulations of the spin dynamics of cryptochrome-inspired radical pairs, they showed that this new scheme offers two clear and important benefits: greatly enhanced sensitivity to a 50 μT magnetic field, and unlike the current model, the radicals can be more than 2 nm apart in the magnetoreceptor protein. This means that animal cryptochromes with a tetrad (rather than a triad) of tryptophan electron donors can still be expected to act as viable magnetic compass sensors. Additionally, lifting the restriction on the rate of spin-selective recombination reaction allows detrimental effects such as inter-radical exchange and dipolar interactions to be minimized by placing the radicals much further apart than in the current model. With these findings, researchers hope to gain further insight into how birds navigate using their remarkable ability to detect magnetic fields.