Stable intermediate phase of secondary structures for semiflexible polymers

Systematic microcanonical inflection-point analysis of precise numerical results obtained in extensive generalized-ensemble Monte Carlo simulations reveals a bifurcation of the coil-globule transition line for polymers with a bending stiffness exceeding a threshold value. The region, enclosed by the toroidal and random-coil phases, is dominated by structures crossing over from hairpins to loops upon lowering the energy. Conventional canonical statistical analysis is not sufficiently sensitive to allow for the identification of these separate phases.

Automated summary

The study shows that a bifurcation of the coil-globule transition line occurs for polymers with a bending stiffness above a threshold value, which is revealed through a systematic microcanonical inflection-point analysis of precise numerical results obtained in extensive generalized-ensemble Monte Carlo simulations. The region between the toroidal and random-coil phases is dominated by structures transitioning from hairpins to loops as the energy decreases. Conventional canonical statistical analysis is unable to identify these separate phases.