  By means of extensive replica-exchange simulations of generic coarse-grained
models for helical polymers, we systematically investigate the structural
transitions into all possible helical phases for flexible and semiflexible
elastic polymers with self-interaction under the influence of torsion barriers.
The competing interactions lead to a variety of conformational phases including
disordered helical arrangements, single helices, and ordered, tertiary helix
bundles. Most remarkably, we find that a bending restraint entails a clear
separation and stabilization of the helical phases. This aids in understanding
why semiflexible polymers such as double-stranded DNA tend to form pronounced
helical structures and proteins often exhibit an abundance of helical
structures, such as helix bundles, within their tertiary structure.
