Modeling force-induced bio-polymer unfolding

Anthony J. Guttmann, Jesper L. Jacobsen, Iwan Jensen, Sanjay Kumar

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


We study the conformations of polymer chains in a poor solvent, with and without bending rigidity, by means of a simple statistical mechanics model. This model can be exactly solved for chains of length up to N = 55 using exact enumeration techniques. We analyze in detail the differences between the constant force and constant distance ensembles for large but finite N. At low temperatures, and in the constant force ensemble, the force-extension curve shows multiple plateaus (intermediate states), in contrast with the abrupt transition to an extended state prevailing in the N → ∞ limit. In the constant distance ensemble, the same curve provides a unified response to pulling and compressing forces, and agrees qualitatively with recent experimental results. We identify a cross-over length, proportional to N, below which the critical force of unfolding decreases with temperature, while above, it increases with temperature. Finally, the force-extension curve for stiff chains exhibits "saw-tooth" like behavior, as observed in protein unfolding experiments.

Original languageEnglish
Pages (from-to)223-237
Number of pages15
JournalJournal of Mathematical Chemistry
Issue number1
Publication statusPublished - 17 May 2008
Externally publishedYes


  • Exact enumerations
  • Lattice models
  • Polymers
  • Protein unfolding


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