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Unfolding times for proteins in a force clamp

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Author

  • Stefano Luccioli
  • Alberto Imparato
  • Simon Mitternacht
  • Anders Irbäck
  • Alessandro Torcini

Summary, in English

The escape process from the native valley for proteins subjected to a constant stretching force is examined using a model for a beta barrel. For a wide range of forces, the unfolding dynamics can be treated as one-dimensional diffusion, parametrized in terms of the end-to-end distance. In particular, the escape times can be evaluated as first passage times for a Brownian particle moving on the protein free-energy landscape, using the Smoluchowski equation. At strong forces, the unfolding process can be viewed as a diffusive drift away from the native state, while at weak forces thermal activation is the relevant mechanism. An escape-time analysis within this approach reveals a crossover from an exponential to an inverse Gaussian escape-time distribution upon passing from weak to strong forces. Moreover, a single expression valid at weak and strong forces can be devised both for the average unfolding time as well as for the corresponding variance. The analysis offers a possible explanation of recent experimental findings for the proteins ddFLN4 and ubiquitin.

Publishing year

2010

Language

English

Publication/Series

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)

Volume

81

Issue

1

Document type

Journal article

Publisher

American Physical Society

Topic

  • Biophysics

Status

Published

ISBN/ISSN/Other

  • ISSN: 1539-3755