Spin-oscillator model for DNA/RNA unzipping by mechanical force

TL;DR

This paper models DNA/RNA unzipping under force using a spin-oscillator system, revealing phase transitions, hysteresis behavior, and force-dependent residence times, providing insights into the mechanical unzipping process.

Contribution

It introduces a novel spin-oscillator model to describe DNA/RNA unzipping, capturing phase transitions and hysteresis phenomena in a unified framework.

Findings

Identifies a first-order phase transition at a critical force $F_c$.

Shows hysteresis in extension at high loading rates.

Demonstrates Arrhenius-like behavior of residence times.

Abstract

We model unzipping of DNA/RNA molecules subject to an external force by a spin-oscillator system. The system comprises a macroscopic degree of freedom, represented by a one-dimensional oscillator, and internal degrees of freedom, represented by Glauber spins with nearest-neighbor interaction and a coupling constant proportional to the oscillator position. At a critical value $F_c$ of an applied external force $F$, the oscillator rest position (order parameter) changes abruptly and the system undergoes a first-order phase transition. When the external force is cycled at different rates, the extension given by the oscillator position exhibits a hysteresis cycle at high loading rates whereas it moves reversibly over the equilibrium force-extension curve at very low loading rates. Under constant force, the logarithm of the residence time at the stable and metastable oscillator rest position is proportional to $(F-F_c)$ as in an Arrhenius law.