Light-activated proteins demonstrate quantum sensing and radio wave control

Until now, quantum sensing has primarily been known from solid-state materials such as diamonds with deliberately introduced tiny defects. The researchers are now transferring this principle to proteins - biological molecules that can be genetically produced and specifically tailored. In the future, this could allow quantum sensors to be built directly into cells or tissue.

These protein-based sensors are potentially particularly well suited for biosensing - that is, for imaging living cells, tissues, or organs. In theory, they sit directly where measurement is needed, making them suitable for studies in organisms - unlike bulky solid-state sensors.

Dominik Bucher, Professor of Quantum Sensing at the TUM School of Natural Sciences and last author of the study published in Nature Biotechnology, explains: "In contrast to established solid-state-based systems, protein-based approaches can not only serve as sensors, but also open up the prospective possibility of controlling biological processes with radio waves in a targeted manner - an extremely exciting prospect."

What exactly did the researchers do?

The researchers irradiated two light-sensitive proteins - so-called flavoproteins - with blue light. The starting point was a cryptochrome, a protein studied in biology as a potential magnetic field sensor in birds. The protein samples used in the study were provided by the research group of Prof. Erik Schleicher at the University of Freiburg.

The light generates spin-correlated radical pairs with extraordinary spin properties in the proteins: these are coupled electron pairs that are extremely sensitive to magnetic fields. This behavior can be made visible via the luminescence intensity of these proteins.

The researchers then deliberately applied radio waves and were able to alter the luminescence of the proteins - and thus the underlying radical pairs. This demonstrates that the sensitive quantum states in the biological environment can be influenced by electromagnetic fields.

The proteins act as magnetic field sensors and can even make magnetic field distributions in the samples visible. The signal is read out purely optically via light - similarly to solid-state-based quantum sensors.

Even though this is basic research, the findings have great potential for near-term biotechnological applications.

The possibilities range from biological quantum sensors to radio wave-controlled cell activity, such as remotely controlled gene expression."

Kun Meng, doctoral student, TUM School of Natural Sciences and first author of the study