Conformations of Linear DNA

TL;DR

This paper models the conformations of under- and overwound linear DNA using an elastic string approach, deriving relations between configuration and topology, and validating with experimental data on plectonemic transitions.

Contribution

It introduces a comprehensive elastic model for DNA conformations that accounts for topology, force, and thermal fluctuations, providing analytical solutions and experimental validation.

Findings

Derived a fundamental relation between Euler angles and linking number.

Obtained analytical expressions for DNA configurations in the infinite-length limit.

Elastic model with thermal fluctuations matches experimental plectonemic transition data.

Abstract

We examine the conformations of a model for under- and overwound DNA. The molecule is represented as a cylindrically symmetric elastic string subjected to a stretching force and to constraints corresponding to a specification of the link number. We derive a fundamental relation between the Euler angles that describe the curve and the topological linking number. Analytical expressions for the spatial configurations of the molecule in the infinite- length limit were obtained. A unique configuraion minimizes the energy for a given set of physical conditions. An elastic model incorporating thermal fluctuations provides excellent agreement with experimental results on the plectonemic transition.