Reconstructing the free-energy landscape of a polyprotein by single-molecule experiments

• Published in: Europhysics letters Vol. 82; no. 5; pp. 58006 - 58006 (5)
• Main Authors: Imparato, A, Sbrana, F, Vassalli, M
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.06.2008; EDP Sciences
• Subjects: 05.70.Ln; 82.37.Rs; 87.15.La
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/82/58006

The mechanical unfolding of an engineered protein composed of eight domains of Ig27 is investigated by using atomic force microscopy. Exploiting a fluctuation relation, the equilibrium free energy as a function of the molecule elongation is estimated from pulling experiments. Such a free energy exhibits a regular shape that sets a typical unfolding length at zero force of the order of 20 nm. This length scale turns out to be much larger than the kinetic-unfolding length that is also estimated by analyzing the typical rupture force of the molecule under dynamic loading.