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Updated: Aug 14, 2026
08:48
Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
Published on: October 13, 2011
Structural transitions in torsionally constrained DNA and their dependence on solution electrostatics
Jaspreet Singh1, Prashant K Purohit1
1Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Acta Biomaterialia
|April 3, 2017
Summary
This study models DNA structural transitions under torsional stress, revealing how ion concentration affects DNA overstretching and phase coexistence. Findings align with experiments and predict new testable outcomes for DNA mechanics.
Area of Science:
- Biophysics
- Molecular Biology
- Computational Biology
Background:
- Torsionally constrained DNA exhibits complex structural transitions, crucial for understanding its in vivo and in vitro behavior.
- DNA's behavior in cells is influenced by packaging and molecular machinery operating in diverse ionic environments.
Purpose of the Study:
- To investigate DNA structural transitions and phase behavior under torsional constraint and external forces.
- To elucidate the impact of ion concentration on DNA overstretching and the coexistence of different DNA phases (B-, S-, and P-DNA).
Main Methods:
- Developed a theoretical model integrating helix-coil transition theory and fluctuating elastic rod theory.
- Incorporated electrostatic interactions between ions and DNA's phosphate backbone.
- Calculated force, torque, and analyzed cooperativity parameters for transitions.
Main Results:
- Modeled the DNA overstretching transition (70% contour length increase) and its dependence on salt concentration.
- Identified conditions for the coexistence of B-, S-, and P-DNA phases.
- Rationalized the non-monotonic dependence of work done on ion concentration via interfacial energy.
Conclusions:
- Theoretical predictions align with experimental data, validating the model.
- The study provides falsifiable predictions for future experimental verification.
- Offers insights into DNA mechanics within cellular environments.
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