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On higher buckling transitions in supercoiled DNA
T Schlick1, W K Olson, T Westcott
1Chemistry Department, New York University, New York 10012.
Biopolymers
|May 1, 1994
Summary
Supercoiled DNA exhibits complex energy and geometric changes with linking number, revealing new dynamic behaviors and configurational transitions. These findings impact our understanding of DNA dynamics at physiological superhelical densities.
Area of Science:
- Biophysics
- Computational Biology
- Molecular Biology
Background:
- Supercoiled DNA plays a crucial role in cellular processes.
- Understanding its dynamics is key to comprehending DNA function.
- Classical elasticity theory provides a framework for DNA behavior.
Purpose of the Study:
- To investigate the energy, geometry, and dynamics of supercoiled DNA.
- To explore configurational transitions and their implications.
- To elucidate the relationship between superhelical density and DNA behavior.
Main Methods:
- Detailed energy minimization simulations.
- Molecular dynamics studies of closed circular DNA.
- Analysis of DNA configurations and energy landscapes.
Main Results:
- Complex dependence of supercoiled DNA energy and geometry on linking number difference (ΔLk).
- Identification of higher-order configurational transitions beyond simple buckling.
- Discovery of multiple energy minima and discontinuous writhing number behavior.
- Observation of rapid interconversions between energetically similar DNA conformations.
- Characterization of distinct timescales for DNA motions, from local residue fluctuations to global tumbling.
Conclusions:
- Supercoiled DNA exhibits intricate behaviors not fully captured by classical theories.
- New insights into DNA dynamics at physiological superhelical densities are provided.
- The findings suggest novel relaxation pathways for nicked DNA and dynamic interconversions between distinct supercoiled states.