Tensile Mechanics of α‑Helical Polypeptides

Abstract

We have developed a statistical mechanical model of the force–extension behavior of α-helical polypeptides, by coupling a random-coil polypeptide elastic model of an inhomogeneous partially freely rotating chain, with the latest version of the helix–coil transition model AGADIR. The model is capable of making quantitatively accurate predictions of force–extension behavior of a given polypeptide sequence including its dependence on pH, temperature and ionic strength. This makes the model a valuable tool for single-molecule protein unfolding experimental studies. Our model predicts the highly reversible unraveling of α-helical structures at small forces of about 20 pN, in good agreement with recent experimental studies