Researchers at Cornell University have identified a new way to measure the torsional stiffness of DNA, that is, how much resistance a helix resists when twisting. This information, they said, could potentially shed light on how cells work. The research is published in Physical Review Letters.
When a motor protein moves forward along the DNA, it must twist or rotate it – i.e. work against the torsional resistance of the spiral. It is these proteins that carry out gene expression or DNA replication as they move along it. If a motor protein encounters too much resistance, it stops. Although scientists know that this rigidity plays a crucial role in the fundamental processes of DNA, its experimental measurement has been difficult.
In a new paper, the researchers report an innovative way to measure the twisting stiffness of DNA. To do this, they measured how difficult it is to twist DNA when the distance from the end to the end of the DNA does not change.
“We came up with a very clever trick for measuring the torsional stiffness of DNA. Intuitively, it seems that DNA will become extremely easy to twist with very little force, ” explains senior study author Michelle Wang, Professor Emeritus of Physics at the Department of Physics at the James Gilbert White College of Arts and Sciences. “We found that both experimentally and theoretically, that is not the case.”
The study authors note that the new method also offers new opportunities for studying twist-induced phase transitions in DNA and the biological consequences of this process.