Proteins as Quantum Sensors: New Advances in Quantum Biology

Context

For decades, fluorescent proteins have allowed scientists to visualise life at the molecular scale. Now, new research shows that through engineering specific electronic states inside these proteins,  can be transformed into genetically encoded quantum sensors capable of detecting magnetic fields and radio waves inside living cells.

Background: From Glowing Proteins to Quantum Tools

• Fluorescent Proteins Revolutionised Biology: The discovery and engineering of Green Fluorescent Protein (GFP) — work recognised with the 2008 Nobel Prize in Chemistry — enabled researchers to track proteins, cells and biological processes in real time.
• How Fluorescent Proteins Work: When illuminated, these proteins absorb light and excite an electron to a higher energy state. As the electron relaxes back, it emits light — producing fluorescence.
• Hidden Quantum Behaviour: Under certain conditions, the excited electron interacts with nearby molecules inside the protein, forming a radical pair — two molecules each with an unpaired electron. The spins of these electrons can become quantum mechanically linked.
  • This spin interaction makes fluorescence subtly sensitive to weak magnetic fields.
• Recent Research: Scientists tweak glowing proteins at the DNA level so that their electrons behave like tiny magnetic sensors — and because the cell makes the protein naturally, the sensor works from inside the living system.

Why Protein-Based Quantum Sensors Matter

Limitations of Solid-State Sensors: Most current quantum sensors use diamond nitrogen-vacancy (NV) centres. While extremely sensitive, they:

• Are rigid solid materials
• Cannot easily be inserted into cells
• Cannot be genetically targeted to specific proteins

Advantages of Genetically Encoded Sensors

Cells can produce these sensors themselves if given the right DNA instructions

Applications

• Magnetic Fields: Detect nanoscale magnetic signals from biochemical reactions involving metal ions.
• Free Radicals: Monitor short-lived radical species involved in metabolism and oxidative stress.
• Enzyme Reactions: Track spin-dependent enzyme processes in respiration and photosynthesis.
• Drug Interactions: Observe how pharmaceuticals alter electronic states in proteins.
• Advanced Imaging: Magnetic modulation allows separation of true signal from background fluorescence (lock-in detection), improving imaging clarity.

Technical Challenges

• Lower Sensitivity: Protein sensors are currently less sensitive than diamond-based systems.
• Shorter Coherence Times: Quantum coherence in biological environments is fragile and short-lived.
• Photobleaching: Repeated light exposure can degrade fluorescent proteins.
• Thermal Noise: Cells are warm and chemically active — environments usually hostile to quantum states.

Yet, history suggests improvement is possible: fluorescent proteins themselves took decades to become robust research tools.

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