Polymer Science Faculty Research


A minimal model for the helix-coil transition of wormlike polymers. insights from Monte Carlo simulations and theoretical implications

Document Type


Publication Date

Fall 2006


We present a geometric approach to the simulation of the helix−coil transition in wormlike polymers. Our approach has its foundations on a novel real-space realization of the concepts proposed by Zimm, Bragg, and other researchers. In our model, the polymer is treated as a freely rotating chain with hard-core repulsion between beads. The conformational state (helix or coil) of each bead is determined by the value of its torsion. If the difference between the torsion of a bead and the one of the perfect helix is less than a cutoff value, then the bead is part of a helical domain and carries a negative energy; otherwise, it is part of a random coil. In addition, interfaces between helical and random coil domains carry an energy penalty. We have simulated these concepts using the Wang−Landau algorithm where the density of states depends on two parameters:  the number of beads in the helical state and the number of interfaces. In this article we show that these simple ideas can account for the cooperativity of the transition explicitly and capture the known conformational, configurational, and thermodynamic properties correctly. Moreover, these concepts have important theoretical implications since they lead naturally to a field-theoretic Hamiltonian of the Edwards' type that might be useful for problems of current experimental interest.



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