Unfolding of globular polymers by external force
Journal of Chemical Physics
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Bell, S., & Terentjev, E. (2015). Unfolding of globular polymers by external force. Journal of Chemical Physics, 143 (184902)https://doi.org/10.1063/1.4935393
We examine the problem of a polymer chain, folded into a globule in poor solvent, subjected to a constant tensile force. Such a situation represents a Gibbs thermodynamic ensemble and is useful for analysing forceclamp atomic force microscopy measurements, now very common in molecular biophysics. Using a basic Flory mean-field theory, we account for surface interactions of monomers with solvent. Under an increasing tensile force a first-order phase transition occurs from a compact globule to a fully extended chain, in an ’all-ornothing’ unfolding event. This contrasts with the regime of imposed extension, first studied by Halperin and Zhulina, where there is a regime of coexistence of a partial globule with an extended chain segment. We relate the transition forces in this problem to the solvent quality and degree of polymerisation, and also find analytical expressions for the energy barriers present in the problem. Using these expressions, we analyse the kinetic problem of a force-ramp experiment, and show that the force at which a globule ruptures depends on the rate of loading.
This work was funded by the Cambridge Theory of Condensed Matter - Critical Mass Grant from EPSRC.
External DOI: https://doi.org/10.1063/1.4935393
This record's URL: https://www.repository.cam.ac.uk/handle/1810/252481
Attribution-NonCommercial 2.0 UK: England & Wales
Licence URL: http://creativecommons.org/licenses/by-nc/2.0/uk/
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