Bending and Twisting Elasticity: a Revised Marko-Siggia Model on DNA Chirality

TL;DR

This paper introduces a revised elastic model for DNA that incorporates chiral twisting energy, predicting how the mean helical repeat length varies with chain length, aligning well with experimental data.

Contribution

It presents a new Marko-Siggia based model including chiral twisting energy, improving understanding of DNA elasticity and helical repeat length behavior.

Findings

Mean HRL increases as DNA chain length decreases for short rings.

Long DNA chains have a consistent HRL regardless of length or end conditions.

Model predictions agree well with experimental observations.

Abstract

A revised Marko-Siggia elastic model for DNA double helix [Macromolecules 27, 981 (1994)] is proposed, which includes the WLC bending energy and a new chiral twisting energy term. It is predicted that the mean helical repeat length (HRL) for short DNA rings increases with the decreasing of chain length; while for very long chains, their mean HRL is the same, independent of both the chain length and whether the ends are closed, it is longer than the value for rectilinear DNAs. Our results are in good agreement with experiments.