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Updated: Jun 18, 2026
07:37
Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase
Published on: September 27, 2024
Discontinuities at the DNA supercoiling transition.
Bryan C Daniels1, Scott Forth, Maxim Y Sheinin
1Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|November 13, 2009
Summary
Researchers observed a sudden change in DNA structure during supercoiling transitions. This study provides experimental evidence and a theory for the coexistence of stretched and plectonemic DNA states.
Area of Science:
- Biophysics
- Molecular Biology
- Polymer Physics
Background:
- DNA supercoiling is crucial for cellular processes.
- Transitions between different DNA conformations are not fully understood.
Purpose of the Study:
- To investigate the abrupt transition during DNA supercoiling.
- To experimentally validate discontinuities in extension and torque.
- To develop a phenomenological theory for coexisting DNA states.
Main Methods:
- Applying constant force to a single DNA molecule.
- Observing supercoiling transitions and plectoneme formation.
- Developing a phenomenological theory and elastic rod simulations.
Main Results:
- Observed a discontinuity at the supercoiling transition.
- Provided experimental evidence for simultaneous stretched and plectonemic DNA states.
- Developed a four-parameter theory that explains experimental observations.
Conclusions:
- The supercoiling transition involves a coexistence of distinct DNA structures.
- The developed theory accurately predicts experimental discontinuities.
- Discrepancies in existing theories are explained by the coexisting state parameters.
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