Reversible Unfolding of Single RNA Molecules by Mechanical Force
Jan Liphardt,1
Bibiana Onoa,1
Steven B. Smith,2
Ignacio Tinoco Jr.,1
Carlos Bustamante12*
Here we use mechanical force to induce the unfolding and
refolding of single RNA molecules: a simple RNA hairpin, a molecule containing a three-helix junction, and the P5abc domain of the Tetrahymena thermophila ribozyme. All three molecules (P5abc
only in the absence of Mg2+) can be mechanically unfolded
at equilibrium, and when kept at constant force within a critical force
range, are bi-stable and hop between folded and unfolded states. We
determine the force-dependent equilibrium constants for
folding/unfolding these single RNA molecules and the positions of their
transition states along the reaction coordinate.
1 Department of Chemistry and
2 Departments of Physics and Molecular and Cell
Biology, Howard Hughes Medical Institute, University of California,
Berkeley, CA 94720, USA.
2 *To whom correspondence should be addressed. E-mail:
jliphard{at}alice.berkeley.gov or JTLiphardt{at}lbl.gov
*
To whom correspondence should be addressed. E-mail:
carlos{at}alice.berkeley.edu
