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Tension-dependent structural deformation alters single-molecule transition kinetics.


ABSTRACT: We analyze the response of a single nucleosome to tension, which serves as a prototypical biophysical measurement where tension-dependent deformation alters transition kinetics. We develop a statistical-mechanics model of a nucleosome as a wormlike chain bound to a spool, incorporating fluctuations in the number of bases bound, the spool orientation, and the conformations of the unbound polymer segments. With the resulting free-energy surface, we perform dynamic simulations that permit a direct comparison with experiments. This simple approach demonstrates that the experimentally observed structural states at nonzero tension are a consequence of the tension and that these tension-induced states cease to exist at zero tension. The transitions between states exhibit substantial deformation of the unbound polymer segments. The associated deformation energy increases with tension; thus, the application of tension alters the kinetics due to tension-induced deformation of the transition states. This mechanism would arise in any system where the tether molecule is deformed in the transition state under the influence of tension.

SUBMITTER: Sudhanshu B 

PROVIDER: S-EPMC3033304 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Tension-dependent structural deformation alters single-molecule transition kinetics.

Sudhanshu B B   Mihardja S S   Koslover E F EF   Mehraeen S S   Bustamante C C   Spakowitz A J AJ  

Proceedings of the National Academy of Sciences of the United States of America 20110118 5


We analyze the response of a single nucleosome to tension, which serves as a prototypical biophysical measurement where tension-dependent deformation alters transition kinetics. We develop a statistical-mechanics model of a nucleosome as a wormlike chain bound to a spool, incorporating fluctuations in the number of bases bound, the spool orientation, and the conformations of the unbound polymer segments. With the resulting free-energy surface, we perform dynamic simulations that permit a direct  ...[more]

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