In situ monitoring of the influence of water on DNA radiation damage by near-ambient pressure X-ray photoelectron spectroscopy

Marc Benjamin Hahn,Paul M Dietrich,Jörg Radnik

doi:10.1038/s42004-021-00487-1

Abstract

Ionizing radiation damage to DNA plays a fundamental role in cancer therapy. X-ray photoelectron-spectroscopy (XPS) allows simultaneous irradiation and damage monitoring. Although water radiolysis is essential for radiation damage, all previous XPS studies were performed in vacuum. Here we present near-ambient-pressure XPS experiments to directly measure DNA damage under water atmosphere. They permit in-situ monitoring of the effects of radicals on fully hydrated double-stranded DNA. The results allow us to distinguish direct damage, by photons and secondary low-energy electrons (LEE), from damage by hydroxyl radicals or hydration induced modifications of damage pathways. The exposure of dry DNA to x-rays leads to strand-breaks at the sugar-phosphate backbone, while deoxyribose and nucleobases are less affected. In contrast, a strong increase of DNA damage is observed in water, where OH-radicals are produced. In consequence, base damage and base release become predominant, even though the number of strand-breaks increases further.

Highlights

Ionizing radiation damage to DNA plays a fundamental role in cancer therapy
Here, we present for the first time simultaneous induction and probing of ionizing radiation damage to DNA by near-ambient pressure (NAP) X-ray photoelectron-spectroscopy (XPS) under H2O and N2 atmospheres, as well as standard ultrahigh vacuum (UHV) conditions (Fig. 1)
Some of the differences observed might be attributed to variation of DNA base sequence, hydration dependent interand intrastrand coupling, conformation, and the local environment between the various studies

Summary

Introduction

Ionizing radiation damage to DNA plays a fundamental role in cancer therapy. X-ray photoelectron-spectroscopy (XPS) allows simultaneous irradiation and damage monitoring. We present near-ambient-pressure XPS experiments to directly measure DNA damage under water atmosphere They permit in-situ monitoring of the effects of radicals on fully hydrated double-stranded DNA. This method was further developed by Kundu et al.[25] by incorporating a separate LEE source to monitor the damage to deoxyadenosine monophosphate via XPS All these studies focused on direct damage by x-ray photons and LEE since they were exclusively performed under UHV conditions. We perform irradiation and simultaneous XPS measurements on fully hydrated DNA This enables the study of changes of damage yields caused by the presence of H2O, via different mechanisms, such as the production of ROS, modification of electron transfer (ET) channels, or conformational changes of DNA

Methods

Results

Conclusion