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Magnetic Tweezers for the Measurement of Twist and Torque
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Extension, torque, and supercoiling in single, stretched, and twisted DNA molecules.

Pui-Man Lam1, Yi Zhen2

  • 1Physics Department, Southern University, Baton Rouge, Louisiana 70813, USA.

The Journal of Chemical Physics
|November 9, 2015
PubMed
Summary

This study refines a model for DNA stretching and supercoiling by incorporating a more accurate free energy function. The improved model achieves quantitative agreement with experimental data across all force regimes.

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Area of Science:

  • Biophysics
  • Molecular Biology
  • Polymer Physics

Background:

  • The Neukirch and Marko model describes DNA extension, torque, and supercoiling.
  • Previous models used an approximate free energy for stretched DNA, leading to qualitative experimental agreement.

Purpose of the Study:

  • To reinvestigate the Neukirch and Marko model using a more accurate free energy for untwisted, stretched DNA.
  • To improve the quantitative agreement between theoretical predictions and experimental observations of DNA mechanical properties.

Main Methods:

  • Revisiting a theoretical model for DNA mechanics.
  • Implementing a refined free energy function for stretched DNA.
  • Comparing model predictions with experimental data across various force regimes.

Main Results:

  • The use of a more accurate free energy function significantly enhances model predictions.
  • The refined model achieves quantitative agreement with experimental data for DNA stretching and supercoiling.
  • The improved agreement holds true throughout the entire force regime studied.

Conclusions:

  • A more accurate free energy function is crucial for quantitatively describing DNA mechanics.
  • The parameter-free theoretical model, when refined, accurately predicts DNA behavior under tension and torsion.
  • This work validates the enhanced model for understanding single DNA molecule behavior.