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Molecular Fluctuations as a Ruler of Force-Induced Protein Conformations

Research output: Contribution to journalArticlepeer-review

Original languageEnglish
Pages (from-to)2953-2961
Number of pages9
JournalNano Letters
Issue number7
Published14 Apr 2021

Bibliographical note

Funding Information: We thank Julio Fernández for his help in building the magnetic tweezers setup and for sharing the plasmid for the talin polyprotein. We thank Ionel Popa for help in assemblying the instrument, and Ainhoa Lezamiz, Palma Rico-Lastres, and Aisling Williams for the engineering of the nesprin polyprotein. This work was supported in part by the Francis Crick Institute which receives its core funding from Cancer Research U.K. (FC001002), the U.K. Medical Research Council (FC001002), and the Wellcome Trust (FC001002). This research was funded in part by the Wellcome Trust [212218/Z/18/Z]. A.E.M.B. is recipient of a Sir Henry Wellcome fellowship (210887/Z/18/Z). This work was supported by the European Commission (Mechanocontrol, Grant Agreement 731957), EPSRC Fellowship K00641 X/1, Leverhulme Trust Research Leadership Award RL-2016-015, Wellcome Trust Investigator Award 212218/Z/18/Z and Royal Society Wolfson Fellowship RSWF/R3/183006 to S.G.M. Publisher Copyright: © 2021 American Chemical Society. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors


Molecular fluctuations directly reflect the underlying energy landscape. Variance analysis examines protein dynamics in several biochemistry-driven approaches, yet measurement of probe-independent fluctuations in proteins exposed to mechanical forces remains only accessible through steered molecular dynamics simulations. Using single molecule magnetic tweezers, here we conduct variance analysis to show that individual unfolding and refolding transitions occurring in dynamic equilibrium in a single protein under force are hallmarked by a change in the protein’s end-to-end fluctuations, revealing a change in protein stiffness. By unfolding and refolding three structurally distinct proteins under a wide range of constant forces, we demonstrate that the associated change in protein compliance to reach force-induced thermodynamically stable states scales with the protein’s contour length increment, in agreement with the sequence-independent freely jointed chain model of polymer physics. Our findings will help elucidate the conformational dynamics of proteins exposed to mechanical force at high resolution which are of central importance in mechanosensing and mechanotransduction.

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