Radiation-induced damage of biological matter is an ubiquitous problem in nature. The influence of the hydration environment is widely discussed, but its exact role remains elusive. Utilising well defined solvated-molecule aggregates, we experimentally observed a hydrogen-bonded water molecule acting as a radiation protection agent for ionised pyrrole, a prototypical aromatic biomolecule. Pure samples of pyrrole and pyrrole(H2O) were outer-valence ionised and the subsequent damage and relaxation processes were studied. Bare pyrrole ions fragmented through the breaking of C-C or N-C covalent bonds. However, for pyrrole(H2O)+, we observed a strong protection of the pyrrole ring through the dissociative release of neutral water or by transferring an electron or proton across the hydrogen bond. Overall, a single water molecule strongly reduces the fragmentation probability and thus the persistent radiation damage of singly-ionised pyrrole.
@article{arxiv.2010.00453,
title = {Water is a radiation protection agent for ionised pyrrole},
author = {Melby Johny and Constant A. Schouder and Ahmed Al-Refaie and Lanhai He and Joss Wiese and Henrik Stapelfeldt and Sebastian Trippel and Jochen Küpper},
journal= {arXiv preprint arXiv:2010.00453},
year = {2024}
}