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Giorgio Favrin, Anders Irbäck, Björn
Samuelsson and Stefan Wallin
Two-State Folding over a Weak Free-Energy
Barrier
Biophysical Journal 85, 1457-1465
(2003)
Abstract
We present a Monte Carlo study of a model protein with 54
amino acids that folds directly to its native
three-helix-bundle state without forming any well-defined
intermediate state. The free-energy barrier separating the
native and unfolded states of this protein is found to be
weak, even at the folding temperature. Nevertheless, we
find that melting curves to a good approximation can be
described in terms of a simple two-state system, and that
the relaxation behavior is close to single exponential. The
motion along individual reaction coordinates is roughly
diffusive on timescales beyond the reconfiguration time for
an individual helix. A simple estimate based on diffusion
in a square-well potential predicts the relaxation time
within a factor of two.
LU TP 03-07
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