We investigate the electron attachment of acetyl chloride CH3COCl (AC) molecules and clusters in a molecular beam experiment and by extensive theoretical calculations. The main product of dissociative electron attachment (DEA) to the AC molecule is Cl-, which leads to the main (AC) n Cl- series in clusters. The weaker ion series identified in the cluster mass spectra correspond to (AC) n HCl2 - and hydrogen abstraction fragments [(AC) n -H]-, in full agreement with calculated energetics. We compare the present results for AC with previously studied trifluoroacetyl chloride CF3COCl (TFAC) and trichloroacetic acid CCl3COOH (TCA) molecules and clusters. DEA of the three isolated molecules results in the main fragment Cl-; however, the electron attachment to their clusters produces distinctly different cluster ions. This demonstrates that the outcomes of reactions of electrons with molecules in an environment cannot easily be predicted from the DEA of isolated molecules, and the solvent plays a key role in the process.

• Publikační typ
• časopisecké články MeSH

Sanazole is a hypoxic radiosensitizer for which the activation mechanism in cells has been suggested to involve initial reduction. Herein, electron attachment to sanazole under isolated conditions and upon microhydrations is investigated. Employing mass spectrometry supported by quantum chemical calculations, the anion formation mechanism and subsequent fragmentation pathways are examined. In the case of electron attachment to the isolated molecule, predominantly dissociative electron attachment is observed. The most prominent fragment anion, (NTR-yl)- at m/z 113, is suggested to be formed in an exothermic pathway through a single-bond dissociation, whereas other intense fragments require structural reorganization. The limited abundance of the parent anion under isolated conditions is altered upon microhydration conditions since in the latter situation only the (microhydrated) parent anion is observed. This result suggests that hydration closes and/or slows down the dissociation process and indicates that for sanazole, the initial mechanism of action in a reductive cell environment may be similar to that of well-studied nitroimidazole radiosensitizers.

• Klíčová slova
• electron attachment, electron‐induced dissociation, radiosensitizer, sanazol,
• MeSH
• elektrony * MeSH
• hmotnostní spektrometrie MeSH
• radiosenzibilizující látky * chemie   MeSH
• triazoly * chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• radiosenzibilizující látky * MeSH
• triazoly * MeSH

Reactivity toward low-energy electrons (LEE) has been hypothesized as a cause of radio-modifying properties for various molecules. LEE's transient nature, however, prevents the establishment of clear links between initial processes at the sub-ps time scale and the final products of radiolysis. Here, such links are explored for the radio-modifying compound RRx-001 (1-bromoacetyl-3,3-dinitroazetidine). Picosecond pulse radiolysis demonstrates the high scavenging capacity of the molecule for secondary quasi-free and solvated electrons forming stable parent anions confirmed by studies of microsolvated RRx-001 in clusters. The anions decay either via auto-detachment of an electron or dissociate involving hydrogen transfer from solvent, resulting in NO2 and 1-(bromoacetyl)-3-nitroazetidine. Surprisingly, no Br dissociation is observed despite its high electron affinity. We assign this behavior to the "inaccessibility" of sigma virtual states for electrons in the solvent, which can be of a general nature.

• Klíčová slova
• catalytic electron, electron attachment, low‐energy electrons, radiosensitizer, state selective,
• Publikační typ
• časopisecké články MeSH

This roadmap reviews the new, highly interdisciplinary research field studying the behavior of condensed matter systems exposed to radiation. The Review highlights several recent advances in the field and provides a roadmap for the development of the field over the next decade. Condensed matter systems exposed to radiation can be inorganic, organic, or biological, finite or infinite, composed of different molecular species or materials, exist in different phases, and operate under different thermodynamic conditions. Many of the key phenomena related to the behavior of irradiated systems are very similar and can be understood based on the same fundamental theoretical principles and computational approaches. The multiscale nature of such phenomena requires the quantitative description of the radiation-induced effects occurring at different spatial and temporal scales, ranging from the atomic to the macroscopic, and the interlinks between such descriptions. The multiscale nature of the effects and the similarity of their manifestation in systems of different origins necessarily bring together different disciplines, such as physics, chemistry, biology, materials science, nanoscience, and biomedical research, demonstrating the numerous interlinks and commonalities between them. This research field is highly relevant to many novel and emerging technologies and medical applications.

• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

We investigate electron attachment to large ammonia clusters doped with a single benzene (Bz) molecule (NH3)N·Bz, N̄ ≈ 320. Negatively charged clusters are probed by mass spectrometry, and the energy-dependent ion yields are derived from mass spectra measured at different electron energies. The ion efficiency curves of pure ammonia clusters exhibit two maxima. At around 6 eV, (NH3)n-1NH2- ions are produced via dissociative electron attachment (DEA) to NH3 molecules. (NH3)n- ions produced at this energy are formed by DEA followed by fragment caging. At low energies around 1.3 eV, only (NH3)n- ions are formed for cluster sizes n ≥ 35 that correspond to solvated electrons in ammonia clusters. The doped (NH3)n·Bz- cluster ions exhibit essentially the same energy dependence. The (NH3)n·Bz- ions are metastable and evaporate NH3 molecule(s), while pure (NH3)n- ions are stable. The lifetime for NH3 molecule evaporation from the Bz-doped clusters was estimated as τ ≈ 18 μs. We interpret the metastability of the doped clusters by the charge localization on a Bz- ion solvated in the ammonia, which is accompanied by an energy release leading to the evaporation of NH3 molecule(s).

• Publikační typ
• časopisecké články MeSH

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.

• Klíčová slova
• clusters, electron attachment, hydration, low-energy electron, metronidazole, radiosensitizer, reduction,
• Publikační typ
• časopisecké články MeSH

We report experimental results of low-energy electron interactions with.

• Klíčová slova
• dissociative electron attachment, low-energy electrons, pyrimidine, radiosensitizer,
• MeSH
• chemické modely MeSH
• dlaždicobuněčné karcinomy hlavy a krku chemie   farmakoterapie   radioterapie   MeSH
• dusíkaté sloučeniny chemie   farmakologie   MeSH
• elektrony * MeSH
• ionizující záření MeSH
• lidé MeSH
• molekulární modely MeSH
• nádorové buněčné linie MeSH
• nádory hypofaryngu chemie   farmakoterapie   radioterapie   MeSH
• pyrimidiny chemie   farmakologie   MeSH
• radiosenzibilizující látky chemie   farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 2,4-dichloropyrimidine MeSH Prohlížeč
• dusíkaté sloučeniny MeSH
• pyrimidiny MeSH
• radiosenzibilizující látky MeSH

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.

• Klíčová slova
• bond formation, clusters, electron attachment, low-energy electron, misonidazole,
• MeSH
• elektrony * MeSH
• misonidazol chemie   MeSH
• molekulární modely MeSH
• molekulární struktura MeSH
• rozpouštědla MeSH
• spektrální analýza MeSH
• teoretické modely MeSH
• voda MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• misonidazol MeSH
• rozpouštědla MeSH
• voda MeSH

While matter is irradiated with highly-energetic particles, it may become chemically modified. Thereby, the reactions of free low-energy electrons (LEEs) formed as secondary particles play an important role. It is unknown to what degree and by which mechanism LEEs contribute to the action of electron-affinic radiosensitisers applied in radiotherapy of hypoxic tumours. Here we show that LEEs effectively cause the reduction of the radiosensitiser nimorazole via associative electron attachment with the cross-section exceeding most of known molecules. This supports the hypothesis that nimorazole is selectively cytotoxic to tumour cells due to reduction of the molecule as prerequisite for accumulation in the cell. In contrast, dissociative electron attachment, commonly believed to be the source of chemical activity of LEEs, represents only a minor reaction channel which is further suppressed upon hydration. Our results show that LEEs may strongly contribute to the radiosensitising effect of nimorazole via associative electron attachment.

• MeSH
• chemoradioterapie * MeSH
• elektrony * MeSH
• lidé MeSH
• nádory terapie   MeSH
• nimorazol chemie   terapeutické užití   MeSH
• oxidace-redukce MeSH
• radiosenzibilizující látky chemie   terapeutické užití   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• nimorazol MeSH
• radiosenzibilizující látky MeSH

In this work, we probe anion production upon electron interaction with Fe(CO)5 clusters using two complementary cluster-beam setups. We have identified two mechanisms that lead to synthesis of complex anions with mixed Fe/CO composition. These two mechanisms are operative in distinct electron energy ranges. It is shown that the elementary decomposition mechanism that has received perhaps the most attention in recent years (i.e., dissociative electron attachment at energies close to 0 eV) becomes suppressed upon increasing aggregation of iron pentacarbonyl. We attribute this suppression to the electrostatic shielding of a long-range interaction that strongly enhances the dissociative electron attachment in isolated Fe(CO)5.

• Klíčová slova
• FEBID, aggregation effects, dissociative electron attachment, iron pentacarbonyl, long-range interactions,
• Publikační typ
• časopisecké články MeSH