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DNA's Mechanical Properties Revealed by Cryo-force Spectroscopy

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DNA's Mechanical Properties Revealed by Cryo-force Spectroscopy

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 such as elasticity and binding properties can be determined. Credit: University of Basel, Department of Physics.
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Physicists at the University of Basel have developed a new method that allows them to study the elasticity and binding properties of DNA molecules on a surface at very low temperatures. Using 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.

DNA is not just a coveted research object because it contains the building instructions for life. It can be used to produce even the smallest components for technical applications. In so-called DNA origami , scientists can manipulate the genetic material in such a way that the folding of DNA strands produces tiny two-dimensional and three-dimensional structures. These are suitable, for example, as a container for pharmaceutical active ingredients, as conductive tubes and as highly sensitive sensors.

Measurement at low temperatures

In order to be able to form the desired shapes, it is important to know the structure as well as the elasticity and the binding forces of the DNA components used. At room temperature, these physical parameters can not be measured because the molecules are constantly in motion.

Not so at low temperatures: The team led by Professor Ernst Meyer from the Swiss Nanoscience Institute and Department of Physics at the University of Basel has for the first time used cryo-force microscopy to characterize DNA molecules and to investigate their binding forces and their elasticity.

Laid off piece by piece

The scientists placed DNA strands of 20 cytosine nucleotides on a gold surface. At a temperature of 5 Kelvin, one end of the DNA strand was then pulled up using the tip of an atomic force microscope. Gradually, the individual components of the strand detach from the surface. The physicists were able to capture their elasticity and the forces needed to release the DNA molecules from the gold surface.

"The longer the detached piece of DNA becomes, the more elastic and softer the DNA becomes," explains lead author Dr. Ing. Rémy Pawlak. This can be explained by the fact that the individual components of the DNA behave like a chain of several interconnected coil springs. Based on the measurements, the researchers were able to determine the spring constant for the individual DNA building blocks.

Computer simulations show that the DNA is discontinuously detached from the surface, which has to do with the breaking up of the bonds of the cytosines to the gold surface and the abrupt movement on the gold surface. The theoretical elasticity values ​​agree very well with the experiments and confirm the model of serially arranged springs.

Snapshot provides insight

The investigations prove that cryo-force spectroscopy is well suited to investigate forces, elasticity and binding properties of DNA strands on surfaces at low temperatures.

"As with cryo-electron microscopy, we take a snapshot with cryo-spectroscopy and gain insight into the properties of DNA," adds Ernst Meyer. "In addition, the scanning probe micrographs could be used to determine nucleotide sequences in the future."

This article has been republished from materials provided by the University of Basel. Note: material may have been edited for length and content. For further information, please contact the cited source.

Rémy Pawlak, Guilherme Vilhena, Antoine Hinaut, Tobias Meier, Thilo Glatzel, Alexis Baratoff, Enrico Gnecco, Ruben Perez, and Ernst Meyer. Conformations and cryo-force spectroscopy of spray-deposited single-strand DNA on gold. Nature Communications (2019), doi : 10.1038 / s41467-019-08531-4.