Twist-induced local curvature of filaments in DNA toroids

TL;DR

This study investigates how twist influences the local curvature of DNA filaments in toroidal bundles, challenging previous assumptions and providing a geometric model to support experimental directions.

Contribution

The paper introduces a geometric model to analyze the effect of twist on filament curvature in DNA toroids, filling a gap in prior assumptions.

Findings

Twist significantly affects local filament curvature.

Model supports the correlation between filament density and curvature.

Results suggest new experimental approaches for DNA toroid studies.

Abstract

DNA toroidal bundles form upon condensation of one or multiple DNA filaments. DNA filaments in toroidal bundles are hexagonally packed, and collectively twist around the center line of the toroid. In a previous study, we and our coworkers argue that the filaments' curvature locally correlates with their density in the bundle, with the filaments less closely packed where their curvature appears to be higher. We base our claim on the assumption that twist has a negligible effect on the local curvature of filaments in DNA toroids. However, this remains to be proven. We fill this gap here, by calculating the distribution of filaments' curvature in a geometric model of twisted toroidal bundle, which we use to describe DNA toroids by an appropriate choice of parameters. This allows us to substantiate our previous study and suggest directions for future experiments.