Magnetic fields are known to influence several biological processes, including bird navigation. However, the energy changes that can be induced by typical magnetic fields are far smaller than typical energies of chemical bonds. A leading hypothesis involves the formation of spin-correlated radical pairs, where coherent singlet-triplet interconversion can modulate reaction dynamics. Through this spin entanglement, static and time-varying magnetic fields can affect biomolecular reactions. Here, we demonstrate that fluorescence from red fluorescent proteins (RFPs) in solution with suitable cofactors can be modulated by a combination of static and radio-frequency (RF) magnetic fields applied near the electron spin resonance frequency at room temperature, both in vitro and in a transgenic C. elegans expressing mScarlet. We further show that magnetic field effects (MFEs) and reaction yield-detected magnetic resonance (RYDMR) can be observed at the neuronal level. Our results suggest that these effects arise from quantum-correlated radical pairs with a coherence time of approximately 4 ns. Moreover, we show that RFP mutations can tune magnetic field sensitivity, providing a strategy to design radical-pair-based systems through directed evolution and rational approaches. Similar effects were observed in engineered light-oxygen-voltage flavin-binding proteins (MagLOVs) and mScarlet-MagLOV fusion proteins. For MagLOVs, the potential ability to couple magnetic field effects with conformational changes could offer a novel approach for gene regulation and downstream protein signaling. For RFPs, magnetic fields provide an external control mechanism for opto-magneto-genetic imaging, enabling localized protein activation and potentially advancing super-resolution imaging.
Bagheri et al. (2026) studied this question.