Two-Sided Impact of Water on the Relaxation of Inner-Valence Vacancies of Biologically Relevant Molecules

Abstract

After ionization of an inner-valence electron of molecules, the resulting cation-radicals store substantial internal energy which, if sufficient, can trigger ejection of an additional electron in an Auger decay usually followed by molecule fragmentation. In the environment, intermolecular Coulombic decay (ICD) and electron-transfer mediated decay (ETMD) are also operative, resulting in one or two electrons being ejected from a neighbor, thus preventing the fragmentation of the initially ionized molecule. These relaxation processes are investigated theoretically for prototypical heterocycle–water complexes of imidazole, pyrrole, and pyridine. It is found that the hydrogen-bonding site of the water molecule critically influences the nature and energetics of the electronic states involved, opening or closing certain relaxation processes of the inner-valence ionized system. Our results indicate that the relaxation mechanisms of biologically relevant systems with inner-valence vacancies on their carbon atoms can strongly depend on the presence of the electron-density donating or accepting neighbor, either water or another biomolecule.

Revealing the Role of N Heteroatoms in Noncovalent Aromatic Interactions by Ultrafast Intermolecular Coulombic Decay

“…This indicates that ICD in the pyridine dimers is mainly due to the 1b 2 /2a 1 band, which corresponds to the ionization of the lowest 2s orbital of carbon (C2 s −1 ). Such states have been shown to decay via ICD just in the non-covalently bonded systems containing electron density rich organic molecules capable of donor−acceptor interactions 38,46,47 as is the case for the systems considered in this paper.…”

How Does Mg2+(aq) Interact with ATP(aq)? Biomolecular Structure through the Lens of Liquid-Jet Photoemission Spectroscopy

“…We contrast the (direct) PE spectra (compare Figure 1 (a)) with nonlocal autoionization electron signal, upon ICD 5 , 13 , 14 , 59 , 60 of Mg 2+ (aq) ions (compare Figure 1 (b)) in the presence of ATP (aq) in their coordination environment. The unique sensitivity to the first hydration shell has been recently demonstrated for Mg 2+ in water 13 which lays the groundwork for the present study.…”