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Force-induced unzipping transitions in an athermal crowded environment
1Institute for Physical Science and Technology, University of Maryland , College Park, Maryland 20742, United States.
The Journal of Physical Chemistry. B
|June 25, 2013
Summary
Macromolecular crowding nonlinearly increases the force needed to unfold a β-hairpin. This critical unfolding force is directly proportional to the osmotic pressure exerted by crowding agents.
Area of Science:
- Biophysics
- Computational Biology
- Polymer Physics
Background:
- Macromolecular crowding significantly influences biological processes within cells.
- Understanding the effects of crowding on protein stability is crucial for cell biology.
Purpose of the Study:
- To investigate the relationship between macromolecular crowding and the mechanical unfolding of β-hairpins.
- To determine how crowding affects the critical unfolding force (Fc).
Main Methods:
- Utilized theoretical arguments and extensive Monte Carlo (MC) simulations.
- Employed a coarse-grained three-dimensional off-lattice model of a β-hairpin.
- Analyzed the dependence of critical force on crowding agent volume fraction (φc) and osmotic pressure (P).
Main Results:
- Critical unfolding force (Fc) increases nonlinearly with crowding agent volume fraction (Fc ≈ φc(α)).
- The exponent α is related to the Flory exponent, linking biopolymer size to amino acid count.
- Fc shows a strong linear dependence on the average osmotic pressure (P) exerted by crowders (correlation coefficient of 0.99657).
Conclusions:
- Macromolecular crowding enhances the mechanical stability of β-hairpins.
- The established linear correlation between Fc and P allows for prediction of unfolding force based on crowder density.
- Findings are experimentally verifiable using laser optical tweezers.
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