Researchers reported in Nature that they have engineered proteins to emit light in response to a combination of weak magnetic fields and pulses of energy at radio frequencies. This could set the stage for tracking proteins in the body with MRI-like instruments with less powerful magnets. The technology could allow researchers to track disease-linked proteins in the body. It could also lead to the development of drugs that could be remotely switched on and off with magnets.
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Researchers at Calico Life Sciences, a biotech company and Alphabet subsidiary, discovered a tiny dimming when a magnetic field is applied to a class of green fluorescent proteins. The researchers boosted the effect using a light-sensitive protein fragment called LOV, which is widely used in optogenetics experiments. The protein fragment is linked to other proteins and then light is applied to change their function.
In a 2024 preprint, the team described how they engineered LOV to respond to magnetic fields by reducing the fluorescence of an attached light-emitting protein, though why this effect was occurring was unclear.
In 2025, a team from Harvard University published a study in the Journal of the American Chemical Society that revealed the hidden cause. When laser light excites to fluorescent proteins, electrons can hop to nearby molecules called flavins that are found in cells, forming pairs of electrons. Electrons in antiparallel pairs are likely to hop back to the protein, giving off excess energy as light. The return of the electrons to the protein can be slowed by adding a magnetic field, which suppresses the formation of electron pairs with antiparallel spins thereby reducing the fluorescence.
In the new study, researchers at the University of Oxford controlled this dimming effect by adding radio-frequency pulses similar to those used in MRI machines. By repeatedly mutating the proteins and selecting the best candidates, they found that some proteins have a large magnetic response with a particular combination of radio-frequency pulses and magnetic fields.
However, the proteins must be excited by a laser to fluoresce, which would be difficult to apply within tissues. Scientists at Nonfiction Laboratories, a startup, say they have engineered magnetic responsiveness into LOV-bound proteins that luminesce in response to a chemical reaction instead of light, making it possible to track specific proteins deep in the body.
