On the Helix-Coil Transition of Wormlike Polymers

We present a geometric approach to the simulation of the Helix-Coil transition in wormlike polymer chains. Our method combines the original concepts proposed by Zimm, Bragg and others with the Monte Carlo method recently developed by Landau and Wang. The wormlike polymer is modeled with the Freely Rotating Chain Model where the beads interact via a hard-core repulsion. For each conformation of the chain, the value of the torsion on each bead was computed using finite differences. The difference between the computed torsion and the ideal torsion of the perfect helix was used as a criterion to determine the conformational state (helix or coil) of each bead. In this way, the cooperative nature of the transition is taken into account explicitly. The coil state was used as the reference state and each bead in the helical state was assigned a negative free energy. Furthermore, interfaces between helical and random coil domains carried a free energy penalty. In this poster, we explore the effects of temperature, length of the polymer chain, stability of the helical state, free energy penalty for the formation of interfaces and the application of a stretching force on the conformational and thermodynamic properties of the polymer chain