Coarse-grained simulations of DNA overstretching

TL;DR

This study uses a coarse-grained DNA model to simulate overstretching, accurately reproducing temperature effects and suggesting force-induced melting as the primary mechanism, while challenging the existence of S-DNA as a simple unstacked duplex.

Contribution

It introduces a coarse-grained simulation approach that captures DNA overstretching behavior and provides insights into the overstretching mechanism and the nature of S-DNA.

Findings

Overstretching occurs at 74 pN in the model, slightly higher than experiments.

The model reproduces temperature dependence of overstretching force.

Overstretching is driven by force-induced melting from free ends.

Abstract

We use a recently developed coarse-grained model to simulate the overstretching of duplex DNA. Overstretching at 23C occurs at 74 pN in the model, about 6-7 pN higher than the experimental value at equivalent salt conditions. Furthermore, the model reproduces the temperature dependence of the overstretching force well. The mechanism of overstretching is always force-induced melting by unpeeling from the free ends. That we never see S-DNA (overstretched duplex DNA), even though there is clear experimental evidence for this mode of overstretching under certain conditions, suggests that S-DNA is not simply an unstacked but hydrogen-bonded duplex, but instead probably has a more exotic structure.