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Anders Irbäck
Protein Folding in the Absence of a Clear
Free-Energy Barrier
Acta Physica Polonica B 34, 4867-4878
(2003)
Abstract
Many small proteins fold in a two-state manner, the
rate-limiting step being the passage of the free-energy
barrier separating the unfolded state from the native one.
The free-energy barrier is, however, weak or absent for the
fastest-folding proteins. Here a simple diffusion picture
for such proteins is discussed. It is tested on a model
protein that makes a three-helix bundle. Assuming the
motion along individual reaction coordinates to be
diffusive on timescales beyond the reconfiguration time for
a single helix, it is found that the relaxation time can be
predicted within a factor of two. It is also shown that
melting curves for this protein to a good approximation can
be described in terms of a simple two-state system, despite
the absence of a clear free-energy barrier.
LU TP 03-37
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