# Thermodynamic Origin of the Linear Pressure Dependence of DNA Thermal Stability

## TL;DR

This paper explains why DNA's thermal stability changes linearly with pressure, linking it to DNA hydration and thermodynamic properties.

## Contribution

The study reveals the thermodynamic origin of DNA's linear pressure dependence through compressibility and expansibility analysis.

## Key findings

- The linear pressure dependence of DNA stability is due to hydration effects on compressibility and expansibility.
- A convergence temperature exists where compressibility and volume of (un)folding become zero.
- Predictions show how temperature and pressure affect DNA's thermodynamic stability parameters.

## Abstract

High pressure affects the structure and function of DNA
and is
a key parameter for studying the origin and physical limits of life.
Different types of DNA structures systematically show a linear pressure
dependence of thermal stability (up to ∼200 MPa), which is
maintained even when the solution composition is changed. The reasons
behind the linear pressure dependence are not understood. We have
performed a thermodynamic analysis of the pressure-, temperature-
and composition-dependent (un)folding of various polynucleotide duplexes
and G-quadruplexes. We demonstrate that the reason for the observed
linearity is the link between compressibility and expansibility, both
of which largely depend on DNA hydration. We predicted the temperature
and pressure dependence of compressibility and expansibility of (un)folding
and explain how they affect the corresponding volume change and thermodynamic
stability parameters. These predictions indicate the existence of
a convergence temperature at which compressibility and volume of (un)folding
simultaneously become equal to zero.