Unraveling DNA tori under tension

TL;DR

This paper presents a model for DNA toroids under tension, revealing a cascade of structural transitions and a force plateau consistent with experimental observations.

Contribution

It introduces a new theoretical model capturing the equilibrium and metastable states of DNA toroids under tension, including transition dynamics.

Findings

DNA toroids are stable up to a critical tension

A cascade of transitions reduces winding number under increasing tension

Model predicts a force plateau matching experimental data

Abstract

Motivated by recent experiments, we develop a model for DNA toroids under external tension. We find that tori are the equilibrium states for our model up to a critical tension, above which they become only metstable. Above this tension, we find a cascade of transitions between discrete toroid states that successively lowers the winding number, until the ground state (rod) is reached. In this process, this model predicts a nearly constant force plateau as a function of extension, in agreement with experiment.