An Asymmetric Mechanism in a Symmetric Molecular Machine
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The calculations reveal a sequential mechanism for contraction/extension in which the asynchronous gliding of each ring is preferred over the concerted movement suggested by chemical intuition. Analysis of the underlying free energy surface indicates that dissymmetric gliding is favored because it entails crossings of much smaller barriers.
Our findings illustrate an important design principle for molecular machines, namely that efficient exploitation of thermal fluctuations may be realized by breaking down the large-scale functional motions into smaller steps.