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Forces and pressures in DNA packaging and release from viral capsids
Shelly Tzlil1, James T Kindt, William M Gelbart
1Department of Physical Chemistry and The Fritz Haber Research Center, The Hebrew University, Jerusalem, Israel.
Biophysical Journal
|March 1, 2003
Summary
DNA packaging in bacteriophage capsids involves immense elastic energy stored in a compressed, spool-like genome. DNA ejection releases this energy, with distinct stages and morphological changes from spool to torus.
Area of Science:
- Biophysics
- Molecular Biology
- Computational Biology
Background:
- Bacteriophage capsids package and eject viral DNA.
- Understanding DNA confinement and release dynamics is crucial.
- Previous work reported preliminary simulation and theory results.
Purpose of the Study:
- To systematically formulate the theory of DNA packaging and ejection forces.
- To investigate the energetic and structural aspects of confined DNA.
- To model the lambda-phage system for numerical results.
Main Methods:
- Developed a theoretical framework for DNA free energy calculation.
- Expressed free energy as contributions from confined and released portions.
- Used variational minimization to determine equilibrium structure and energy.
Main Results:
- Fully encapsidated DNA forms a compressed, spool-like condensate storing significant elastic energy.
- DNA ejection involves two stages: rapid stress release followed by morphological transformation.
- Calculated loading force, capsid pressure, and pressure profiles, showing good agreement with experiments.
Conclusions:
- The study provides a comprehensive theoretical and numerical analysis of DNA packaging and ejection.
- Energetic and structural properties of confined DNA dictate ejection dynamics.
- Results offer insights into the forces and pressures involved in viral DNA delivery.