Using Fluorescent Proteins that are Sensitive to Magnetic Fields as Quantum Biosensors

The Science

Magnetic fields influence several biological processes, possibly including humans' circadian rhythms and how birds perceive magnetic fields. This influence occurs through spin quantum effects due to reactions that generate correlated pairs of free radicals (ions, molecules, or atoms with unpaired electrons). Weak magnetic fields can subtly change how the electron spin states in paired radicals evolve. That evolution can change the quantum spin states in the free radicals, which can then shift which biochemical reaction pathways follow in an organism. In this study, scientists discovered that weak magnetic fields affect the brightness of fluorescent proteins involving free radicals. They found that a reaction that involves these proteins generates a correlated radical pair. Scientists can then use magnetic fields to control these radicals and affect the proteins' brightness to serve as a quantum biosensor. They even observed this effect in live animals.

The Impact

Scientists use fluorescent proteins to take optical (or light-based) images of and control biological systems. However, light can only penetrate so far. This limit restricts how thick samples can be. In contrast, magnetic fields can penetrate much deeper into samples. As a result, magnetic field-based imaging tools could potentially address certain limitations of optics-based methods. This study provides a potential new method of using magnetic fields' effects on the brightness of fluorescent proteins for quantum biosensing, imaging and remote control of biomolecular processes. Scientists could use this quantum sensing to study processes including interactions between plants, bacteria, and fungi. These results also suggest the broader potential for using quantum tools in biology.

Summary

Researchers have demonstrated that bringing a small magnet close to solutions containing a red fluorescent protein (RFP) called mScarlet and a blue-light-sensitive cofactor, flavin mononucleotide (FMN), significantly reduces RFP's fluorescence levels. Researchers must pre-excite the solution with blue light, which excites FMN. They follow that step with green light activation to induce RFP excitation for fluorescence generation. When the scientists apply the magnetic field, the fluorescence intensity decreases and this can be selectively modulated with a resonant radio frequency field. Once the magnetic fields are removed, the fluorescence returns to normal. This effect can be repeated for many minutes. The researchers also showed that transgenic Caenorhabditis elegans nematodes, which express the mScarlet quantum biosensor in their bodies or specific tissues, exhibit these magnetic field effects.

The leading hypothesis suggests that the magnetic field influences the dynamics of spin-correlated radical pairs in living systems. Researchers confirmed that time-varying magnetic fields near the radio frequency corresponding to its electron spin resonance can restore the mScarlet fluorescence intensity in mScarlet in solutions or genetically modified nematodes. Researchers also observed magnetic field effects in bacteria expressing the FMN-containing protein MagLOV. These findings support the spin-correlated radical pair mechanism. They open exciting possibilities for using this quantum sensing effect in future imaging and control of biological processes and broader potential for quantum tools in biology.

Contact

Soichi Wakatsuki
SLAC, Stanford University
[email protected]

Mark Kasevich
Stanford University
[email protected]

Steven Boxer
Stanford University
[email protected]

Funding

This work was supported by the Department of Energy (DOE) Office of Science, Biological and Environmental Research program. Additional funding was provided by the National Institutes of Health (NIH) and the Stanford Bio-X Bowes Graduate Student Fellowship.

Publications

Burd, S.C., Bagheri, N., Condon, A.F. et al. "Magnetic resonance control of spin-correlated radical pair dynamics in vivo." Nature 651, 940-945 (2026). [https://doi.org/10.1038/s41586-026-10282-4]