# A TDDFT-based Study on the Proton-DNA Collision

## TL;DR

This study uses time-dependent density functional theory (TDDFT) to simulate proton-DNA collisions, revealing how energy transfer causes base damage and backbone breaks, with implications for understanding radiation effects on DNA.

## Contribution

It applies TDDFT with Ehrenfest dynamics to model proton interactions with DNA at an atomic level, providing detailed insights into damage mechanisms.

## Key findings

- Base damage occurs at 17.9 eV impact energy.
- Backbone breaks at around 60 eV impact energy.
- Damage to bases often accompanies backbone breaks.

## Abstract

The interaction of heavy charged particles with DNA is of interest for several areas, from hadrontherapy to aero-space industry. In this paper, a TD-DFT study on the interaction of a 4 keV proton with an isolated DNA base pair was carried out. Ehrenfest dynamics was used to study the evolution of the system during and after the proton impact up to about 193 fs. This time was long enough to observe the dissociation of the target, which occurs between 80-100 fs. The effect of base pair linking to the DNA double helix was emulated by fixing the four O3' atoms responsible for the attachment. The base pair tends to dissociate into its main components, namely the phosphate groups, sugars and nitrogenous bases. A central impact with energy transfer of 17.9 eV only produces base damage while keeping the backbone intact. An impact on a phosphate group with energy transfer of about 60 eV leads to backbone break at that site together with base damage, while the opposite backbone site integrity is kept is this situation. As the whole system is perturbed during such a collision, no atom remains passive. These results suggest that base damage accompanies all backbone breaks since hydrogen bonds that keep bases together are much weaker that those between the other components of the DNA.