Unique interaction between terahertz radiation and proteins

Thanks to modern terahertz technology and X-ray crystallography, researchers at the University of Gothenburg and Chalmers in collaboration with German researchers, have now seen that the 50-year old predictions made by quantum physicist Herbert Fröhlich that a condensation could be formed in biological systems would appear to be correct. “Our studies open the door to far wider-ranging studies on the effect of terahertz radiation on proteins,” says Gergely Katona, project manager and researcher at the University of Gothenburg.

Gergely Katona, GU.If you cool down atoms as much as possible, they will enter a state of extremely low energy and low-frequency vibrations. In 1968 the physicist herbert Fröhlich predicted that a similar process at higher temperatures could concentrate all of the vibrational energy found in a biological system  into its lowest-frequency vibrational mode.

An initial breakthrough
Researchers in Sweden and Germany have the first experimental evidence of what is known as Fröhlich condensation. The results have now been reported in the journal Structural Dynamics, which highlights their research article.

In the experiment, the researchers used a combination of terahertz technology and X-ray crystallography whereby terahertz radiation and X-rays were able simultaneously to penetrate a crystal formed by the lysozyme protein, which is found in egg white.

The interaction between the protein crystal and the X-rays meant that the researchers were able to calculate the relative density of electrons in different locations in the sample material which could then be used to describe the position of atoms and molecules.

Ida Lundholm, GU.“We have shown for the first time how terahertz radiation can change the local density of electrons in a protein; this opens the door to studies on the properties of proteins which can take a totally new perspective,” says Ida Lundholm at the University of Gothenburg, who is the lead author of the article together with her colleague Helena Rodilla at Chalmers.

Terahertz radiation occupies the space in the electromagnetic spectrum between microwaves and infrared light. The interaction between the vibration-rotation transitions of molecules and terahertz radiation have long been studied by radio astronomers to provide us with knowledge about the composition and development of the universe.

“Our results now show that terahertz technology can also be a unique tool for understanding and mapping the most minute building blocks of our biological makeup,” says Jan Stake, Professor in Terahertz Electronics at Chalmers.

Helena Rodilla, Chalmers.Opening the door to more studies
The studies of Fröhlich condensation open the door to  far wider-ranging studies of the effect of terahertz radiation on proteins. The theoretical underpinnings are relatively simple, believes Gergely Katona, senior researcher at the Department of Chemistry and Molecular Biology at the University of Gothenburg.

“Fröhlich predicted that photons in the terahertz domain can stimulate a resonance and coherent low-frequency movement in large molecules. What is fascinating is that a truly minute amount of energy added by the THz photons can bring the vibrating molecules to form a shared ground state, whereby the molecule vibrate at lowest-frequency vibrational mode. Other models, however, predict that the protein quickly dissipates the energy from the photon in the form of heat,” says Gergely Katona.


Jan Stake, Chalmers.Contacts:

Gergely Katona, Department of Chemical and Molecular Biology, the University of Gothenburg, Tel: +46 31-786 3959, E-mail: gergely.katona@gu.se   
Jan Stake, Professor at Chalmers University of Technology, tel: +46 31-772 18 36, E-mail:  jan.stake@chalmers.se
 
Structural Dynamics is a scientific journal on research methods and techniques
sd.aip.org

Link to the article >>>
scitation.aip.org/content/aip/journal/sdy/2/5/10.1063/1.4931825

Photo:
Picture 1: Lysozyme molecules arranged in a crystal lattice. The red helical structures are associated with electron density changes when the protein crystal is exposed to terahertz radiation.
Picture 2: Picture of Gergely Katona, GU
Picture 3: Picture of Ida Lundholm, photo Francesco Benzi
Picture 4: Picture of Jan Stake, photo Jan-Olof Yxell
Picture 5: Picture of Helena Rodilla, Chalmers

Published: Wed 29 Mar 2017.