Role of the Kinetic Relation in a Phase Transition-Based Model for Mechanical Unfolding in Macromolecules

Abstract

We present applications of a model developed to describe unfolding in macromolecules under an axial force. We show how different experimentally observed force-extension behaviors can be reproduced within a common theoretical framework. We propose that the unfolding occurs via the motion of a folded/unfolded interface along the length of the molecule. The molecules are modeled as one-dimensional continua capable of existing in two metastable states under an applied tension. The interface separates these two metastable states and represents a jump in stretch, which is related to applied force by the worm-like-chain relation. The mechanics of the interface are governed by the Abeyaratne-Knowles theory of phase transitions. The thermodynamic driving force controls the motion of the interface via an equation called the kinetic relation. By choosing an appropriate kinetic relation for the unfolding conditions and the macro-molecule under consideration, we have been able to generate a variety of unfolding processes in macromolecules.