DNA twist stability changes with magnesium(2+) concentration

TL;DR

This study investigates how magnesium ion concentration influences the stability of DNA's helical twist, revealing stabilization effects at higher magnesium levels through analysis of force-extension data.

Contribution

The paper introduces a new fitting approach for force-extension data and demonstrates the impact of magnesium ions on DNA twist stability, extending current DNA elasticity models.

Findings

DNA twist is stabilized at high magnesium concentrations.

A robust fitting method for force-extension data was developed.

Magnesium ions affect DNA's mechanical properties.

Abstract

For an understanding of DNA elasticity at high mechanical loads (F > 30 pN), its helical nature needs to be taken into account, in the form of coupling between the twist and stretch degrees of freedom. The prevailing model for DNA elasticity, the worm-like chain, was previously extended to include this twist-stretch coupling, giving rise to the twistable worm-like chain. Motivated by DNA's charged nature, and the known effects of ionic charges on the molecule's persistence length and stretch modulus, we explored the impact of buffer ionic conditions on twist-stretch coupling. After developing a robust fitting approach for force-extension data, we find that DNA's helical twist is stabilized at high concentrations of the magnesium divalent cation.