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Anders Irbäck, Simon Mitternacht and Sandipan
Mohanty
Dissecting the Mechanical Unfolding of
Ubiquitin
Proceedings of the National Academy of Sciences
USA 102, 13427-13432 (2005)
Abstract
The unfolding behavior of ubiquitin under the influence
of a stretching force was recently investigated
experimentally by single-molecule constant-force methods.
Many observed unfolding traces had a simple two-state
character, whereas others showed clear evidence of
intermediate states. Here we use Monte Carlo (MC)
simulations to investigate the force-induced unfolding of
ubiquitin at the atomic level. In agreement with
experimental data, we find that the unfolding process can
occur either in a single step or via intermediate states.
In addition to this randomness, we find that many
quantities, such as the frequency of occurrence of
intermediates, show a clear systematic dependence on the
strength of the applied force. Despite this diversity,
one common feature can be identified in the simulated
unfolding events, which is the order in which the
secondary-structure elements break. This order is the
same in two- and three-state events, and at the different
forces studied. The observed order remains to be verified
experimentally but appears physically reasonable.
LU TP 05-06
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