Force-induced conformational transition in a system of interacting stiff polymers: application to unfolding

We consider a stiff polymer chain in poor solvent and apply a force at one end of the chain. We find that by varying the stiffness parameter, the polymer undergoes a transition from the globule state to the foldedlike state. The conformation of the folded state mimics the β sheet as seen in the titin molecule. Using the exact enumeration technique, we study the extension-force and force-temperature diagrams of such a system. The force-temperature diagram shows the re-entrance behavior for a flexible chain. However, for a stiff chain this re-entrance behavior is absent and there is an enhancement in θ temperature with the rise of stiffness. We further propose that the internal information about the frozen structure of a polymer can be read from the distribution of end-to-end distance which shows a sawtoothlike behavior