What is a Fluorescent Protein? From a Historic Achievement to a Quantum Future

Context

• Fluorescent proteins, which have been a staple of scientific research for decades, are now undergoing a revolutionary transformation. Recent research suggests that these luminous indicators are no longer limited to visual images, but are also capable of performing complex quantum computation and sensing within living cells.

What is a Fluorescent Protein?

• Fluorescent proteins (FPs) are macromolecular probes that can be defined as proteins capable of generating fluorescence through the spontaneous formation of a fluorophore from certain amino acid residues.
• This allows specific molecular processes, organs, and organisms to be observed in their natural state.
• Due to their high quantum yield, light stability, and diverse emission spectrum, they are widely used in biological studies.

From a Historic Achievement to a Quantum Future

• Fluorescent proteins gave biology the "vision" for which they were awarded the 2008 Nobel Prize in Chemistry. Their role has been unparalleled, from monitoring cancer cells to mapping the brain's neural networks.
• But two new studies published in the prestigious journal Nature have revealed a surprising fact: these proteins can be genetically modified to become "quantum sensors."
• Until now, quantum technology was considered a relic of the sub-zero temperatures and controlled environments of laboratories. The belief was that the warm and dynamic environment of a living cell was detrimental to "quantum states." These new studies have shattered this myth.

The Quantum Mechanism Behind the Glow: Spin and Radical Pairs

• When a fluorescent protein absorbs light, its electrons are excited to higher energy levels. During this process, radical pairs are formed in certain proteins.
• Electron spin: The spins of the electrons in these molecules are interconnected.
• Magnetic sensitivity: Even subtle magnetic effects can affect the behavior of these electrons. This is why the intensity of protein fluorescence changes when the external magnetic field changes. Scientists believe that this mechanism is how many migratory birds and animals are able to sense the Earth's magnetic field.

Two major pillars of research: EYFP and MagLOV

1.University of Chicago: Protein becomes a 'Qubit'

• Researchers at the Pritzker School of Molecular Engineering experimented with EYFP (Enhanced Yellow Fluorescent Protein). They controlled the protein's electron spin using laser pulses and microwave waves.
• Achievement: They successfully completed the sequence required for a quantum computer's qubit.
• Result: This effect was observed not only in cold environments but also at normal temperatures within E. coli bacteria, providing evidence of quantum stability in a biological environment.

2.Oxford University: Development of MagLOV

• The Oxford team developed a new protein family called 'MagLOV' using plant proteins.
• Technology: Through genetic engineering and selection, versions were created that are highly sensitive to radio waves.
• Significance: These proteins can modulate their brightness through radio waves, allowing movements within cells to be directly observed using magnetic resonance.

Why is this important in biological environments?

• Traditional quantum sensors made from solid materials, such as diamond, are highly accurate, but fitting them precisely within cells is difficult. In contrast, protein-based sensors have several advantages:
• Self-fabrication: Cells can make them themselves based on DNA instructions.
• Precise targeting: They can be attached to specific enzymes or cell organelles (such as mitochondria).
• Microscopic studies: They are capable of measuring electronic changes occurring during processes such as enzyme reactions, free radical formation, and respiration.

Future prospects and challenges

• Researchers have demonstrated that clear imaging can be achieved even in noisy environments using a 'lock-in detection' technique. This technology could revolutionize the following areas in the future:
• Drug effects: Tracking how drugs change protein structure at the molecular level.
• Biochemical monitoring: Real-time measurement of temperature and electric fields within cells.
• Advanced diagnostics: Taking high-level imaging like MRI to the nanoscale.
• However, technical hurdles such as short coherence time and photobleaching (fading of the protein's brightness) still remain. Nevertheless, just as fluorescent proteins took time to become an essential part of the laboratory, these biological-quantum hybrid sensors will chart a new course for the future of medicine and biology.