Physicists from the University of Basel have developed a new method to examine the elasticity and binding properties of DNA molecules on a surface at extremely low temperatures. With a combination of cryo-force spectroscopy and computer simulations, they were able to show that DNA molecules behave like a chain of small coil springs. The researchers reported their findings in Nature Communications ("Conformations and cryo-force spectroscopy of spray-deposited single-strand DNA on gold").
At low temperatures, a DNA strand is removed from the gold surface using the tip of an atomic force microscope. In the process, physical parameters can be determined.
Image: University of Basel, Department of Physics
The same is not true at low temperatures: the team led by Professor Ernst Meyer from the Swiss Nanoscience Institute and the University of Basel’s Department of Physics have now used cryo-force microscopy for the first time to characterize DNA molecules and examine their binding forces and elasticity.
“The longer the detached piece of DNA, the softer and more elastic the DNA segment becomes,” explains lead author Dr. Rémy Pawlak. This is because the individual components of the DNA behave like a chain of multiple coil springs connected to one another. Thanks to the measurements, the researchers were able to determine the spring constant for the individual DNA components.
Computer simulations clarify that the DNA is detached discontinuously from the surface. This is due to the breaking up of bonds between the cytosine bases and the DNA backbone from the gold surface, and their abrupt movements over the gold surface. The theoretical elasticity values correlate very closely with the experiments and confirm the model of serially arranged springs.
“As with cryogenic electron microscopy, we take a snapshot with cryo-force spectroscopy, which gives us an insight into the properties of DNA,” explains Meyer. “In future, we could also make use of scanning probe microscope images to determine nucleotide sequences.”
Universität Basel. Posted: Feb 08, 2019.