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Ultrafast folding kinetics and cooperativity of villin headpiece in single-molecule force spectroscopy

TitleUltrafast folding kinetics and cooperativity of villin headpiece in single-molecule force spectroscopy
Publication TypeJournal Article
Year of Publication2013
AuthorsZoldak, G, Stigler, J, Pelz, B, Li, H, Rief, M
JournalPROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume110
Pagination18156-18161
Date PublishedNOV 5
ISSN0027-8424
Abstract

In this study we expand the accessible dynamic range of single-molecule force spectroscopy by optical tweezers to the microsecond range by fast sampling. We are able to investigate a single molecule for up to 15 min and with 300-kHz bandwidth as the protein undergoes tens of millions of folding/unfolding transitions. Using equilibrium analysis and autocorrelation analysis of the time traces, the full energetics as well as real-time kinetics of the ultrafast folding of villin headpiece 35 and a stable asparagine 68 alanine/lysine 70 methionine variant can be measured directly. We also performed Brownian dynamics simulations of the response of the bead-DNA system to protein-folding fluctuations. All key features of the force-dependent deflection fluctuations could be reproduced: SD, skewness, and autocorrelation function. Our measurements reveal a difference in folding pathway and cooperativity between wild-type and stable variant of headpiece 35. Autocorrelation force spectroscopy pushes the time resolution of single-molecule force spectroscopy to similar to 10 mu s thus approaching the timescales accessible for all atom molecular dynamics simulations.

DOI10.1073/pnas.1311495110