Ring formation and hydration effects in electron attachment to misonidazole

This research was funded by CZECH SCIENCE FOUNDATION grant number 19-01159S; Czech Ministry of Education Youth and Sports via OP RDE Grant no. CZ.02.2.69/0.0/16_027/0008355; S.D. acknowledges funding from the FWF, Vienna (P30332).We study the reactivity of misonidazole with low-energy electrons in a water environment combining experiment and theoretical modelling. The environment is modelled by sequential hydration of misonidazole clusters in vacuum. The well-defined experimental conditions enable computational modeling of the observed reactions. While the NO- 2 dissociative electron attachment channel is suppressed, as also observed previously for other molecules, the OH- channel remains open. Such behavior is enabled by the high hydration energy of OH- and ring formation in the neutral radical co-fragment. These observations help to understand the mechanism of bio-reductive drug action. Electron-induced formation of covalent bonds is then important not only for biological processes but may find applications also in technology.publishersversionpublishe

Dissociative electron attachment to methyl isocyanide

We experimentally probed the dissociation of methyl isocyanide, CH$$_3$$NC, via low-energy electron attachment. We have measured the absolute dissociative electron attachment (DEA) cross section for each of the produced ions as a function of incident electron energy. We were able to observe the CH$$_2^-$$, CH$$_3^-$$, CN$$^-$$, CNC$$^-$$, CHNC$$^-$$ and CH$$_2$$NC$$^-$$ anionic fragments as DEA products. Our experimental results are consistent with a previous report, and in addition, we observed the CH$$_2^-$$ anion for the first time. To support these experimental results, we also have performed density functional theory (DFT) calculation at the B3LYP/aug-cc-pVTZ level of theory to find out which reaction channel(s) lead to the formation of a given anion

Dissociative attachment of low-energy electrons to acetonitrile

We experimentally probed the low-energy electron-induced dissociation of acetonitrile and acetonitrile-$$\hbox {d}_3$$ and performed density functional theory calculations to support the experimental results. The previous studies on electron attachment to acetonitrile presented a number of contradictory findings, which we aimed to resolve in the present study. We observed the formation of $$\hbox {H}^-$$, $$\hbox {CH}_2^-$$, $$\hbox {CH}_3^-$$, $$\hbox {CN}^-$$, $$\hbox {CCN}^-$$, $$\hbox {CHCN}^-$$ and $$\hbox {CH}_2 \hbox {CN}^-$$ anions and the corresponding deuterated fragments for acetonitrile-$$\hbox {d}_3$$ by dissociative electron attachment, and measured ion yields curves of each fragment. We saw no evidence for associative electron attachment to form the parent ion in these measurements. We also have measured the kinetic energy and angular distribution of selected fragments using a velocity map imaging (VMI) spectrometer

Low-Energy Electron Induced Reactions in Metronidazole at Different Solvation Conditions

Metronidazole belongs to the class of nitroimidazole molecules and has been considered as a potential radiosensitizer for radiation therapy. During the irradiation of biological tissue, secondary electrons are released that may interact with molecules of the surrounding environment. Here, we present a study of electron attachment to metronidazole that aims to investigate possible reactions in the molecule upon anion formation. Another purpose is to elucidate the effect of microhydration on electron-induced reactions in metronidazole. We use two crossed electron/molecular beam devices with the mass-spectrometric analysis of formed anions. The experiments are supported by quantum chemical calculations on thermodynamic properties such as electron affinities and thresholds of anion formation. For the single molecule, as well as the microhydrated condition, we observe the parent radical anion as the most abundant product anion upon electron attachment. A variety of fragment anions are observed for the isolated molecule, with NO2− as the most abundant fragment species. NO2− and all other fragment anions except weakly abundant OH− are quenched upon microhydration. The relative abundances suggest the parent radical anion of metronidazole as a biologically relevant species after the physicochemical stage of radiation damage. We also conclude from the present results that metronidazole is highly susceptible to low-energy electrons

Supporting alternative strategies for learning chemical applications of group theory

A group theory course for chemists was taught entirely with process oriented guided inquiry learning (POGIL) to facilitate alternative strategies for learning. Students completed a test of one aspect of visuospatial aptitude to determine their individual approaches to solving spatial tasks, and were sorted into groups for analysis on the basis of their aptitude. Affective constructs from self-determination theory relating to motivation were also assessed. Students without strong visuospatial skills found the activities more interesting and enjoyable than students who could successfully complete spatial tasks. Equally successful outcomes were observed on an assessment task, irrespective of visuospatial aptitude of the student. This illustrates that a pedagogy structured around multiple strategies for reasoning can successfully support alternative approaches to abstract concepts, such as chemical applications of group theory