Distribution Functions, Loop Formation Probabilities and Force-Extension Relations in a Model for Short Double-Stranded DNA Molecules

TL;DR

This paper uses transfer matrix methods to analyze the distribution, loop formation, and force-extension behavior of short double-stranded DNA, highlighting the impact of bubbles and sequence heterogeneity on these properties.

Contribution

It introduces an analytic formula for loop formation probability considering bubbles and demonstrates sequence-dependent effects in short DNA molecules.

Findings

Bubbles significantly alter the end-to-end distance distribution.

Loop formation probabilities depend strongly on DNA sequence.

Unusual force-extension curves are observed due to bubbles.

Abstract

We obtain, using transfer matrix methods, the distribution function $P(R)$ of the end-to-end distance, the loop formation probability and force-extension relations in a model for short double-stranded DNA molecules. Accounting for the appearance of ``bubbles'', localized regions of enhanced flexibility associated with the opening of a few base pairs of double-stranded DNA in thermal equilibrium, leads to dramatic changes in $P(R)$ and unusual force-extension curves. An analytic formula for the loop formation probability in the presence of bubbles is proposed. For short {\em heterogeneous} chains, we demonstrate a strong dependence of loop formation probabilities on sequence, as seen in recent experiments.