Irreversible topological transition of a stretched superhelix: the interplay of chiralities.

Helical complexes with certain intramolecular constraints on their topological state, exhibit nontrivial conformational changes in response to an external tension. We consider a generic right-handed helix and construct identical right and left-handed superhelixes. By using molecular dynamics simulations, we discover that under an external tension, the interplay between the helix chirality and the chirality of the superhelix leads to a fundamental topology transition of the stretched right-handed superhelix to its left-handed counterpart. We characterize and rationalize this irreversible phenomenon for a wide range of intramolecular angular stiffnesses and determine the associated phase diagram at different external loadings.