First Quantum Coherence In Biological Molecule

Schematic of lysozyme molecules arranged in a crystal lattice. The red helical structures are associated with increases in electron density when the protein crystal was exposed to terahertz radiation. Gergely Katona, et al.

A protein has shown signs of quantum coherence, suggesting it is briefly forming the bizarre state of matter in which the "Alice in Wonderland" world of quantum mechanics occurs at larger scales. While the observations are still indirect, they could open up exciting opportunities for exploring both the structure of biological molecules and quantum behavior on macroscopic scales.

At extremely low temperatures, atoms sometimes join together to behave like a single electron or photon. Known as Bose-Einstein condensate, the phenomenon sees relatively large objects behave with the mix of wave and particle behavior that allows subatomic particles to bewilder anyone used to thinking of physics on human scales. 

Bose-Einstein condensate is normally made with atoms of a single element (such as rubidium), but in 1968, when Bose-Einstein condensate was still theoretical, physicist Herbert Fröhlich predicted that the same thing could occur in biological proteins. Forty-seven years later, a paper in Structural Dynamics has announced evidence for what is now called Fröhlich condensate.

"Observing Fröhlich condensation opens the door to a much wider-ranging study of what terahertz radiation does to proteins," said senior author Dr. Gergely Katona of the University of Gothenburg in a statement.

Katona and his colleagues applied terahertz radiation (between microwaves and infrared) to crystalized lysozyme molecules extracted from egg whites. Lysozymes occur in humans as well, being used by the immune system to fight off bacteria. The team found that 0.4 THz of electromagnetic radiation caused the lysozyme to vibrate in its lowest-frequency mode

Electron density increased when the radiation was focused on lysozyme crystals, indicating helices within the molecule were compressed, and stayed that way for at least 25 microseconds. This is consistent with Fröhlich's predictions, but thousands to millions of times longer than alternative models, which suggest that any energy acquired from the radiation would dissipate very rapidly.

The observations fall far short of witnessing egg white proteins behaving as waves in double slit experiments or other such mind-twisting demonstrations of quantum behavior. However, Katona considers the findings just the beginning in revealing how proteins respond to radiation of this sort, particularly if more sustained compression can be achieved.

Katona attributed the delay in testing Fröhlich's theories to the challenges of working with terahertz radiation, a newly growing area

Other proteins are expected to have similar responses to appropriate frequencies in the terahertz range, but the paper notes, “Collective vibrations in the terahertz regime are difficult to identify because more atoms are involved in the absorption process and the absorption also depends on the three-dimensional arrangement of the polypeptide chain.” This makes it hard to match proteins with the resonant frequency required to stimulate them.

Fröhlich condensate has been suggested as an explanation for consciousness by the great mathematician Roger Penrose. This has made it popular with woo practitioners who attribute magical powers to “quantum vibrations.” However, since few of us have ever encountered terahertz radiation of anything like this intensity, this project doesn't support these claims, although it probably won't stop people from trying.

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