scholarly journals Reactions in the Radiosensitizer Misonidazole Induced by Low-Energy (0–10 eV) Electrons

2019 ◽  
Vol 20 (14) ◽  
pp. 3496 ◽  
Author(s):  
Rebecca Meißner ◽  
Linda Feketeová ◽  
Eugen Illenberger ◽  
Stephan Denifl
Keyword(s):  
Electron Energy ◽  
Multiple Bond ◽  
Electron Attachment ◽  
Low Energy ◽  
Hypoxic Cell ◽  
Narrow Resonance ◽  
Molecular Anion ◽  
Physical Chemical ◽  
Low Energy Electrons ◽  
Molecular Description

Misonidazole (MISO) was considered as radiosensitizer for the treatment of hypoxic tumors. A prerequisite for entering a hypoxic cell is reduction of the drug, which may occur in the early physical-chemical stage of radiation damage. Here we study electron attachment to MISO and find that it very effectively captures low energy electrons to form the non-decomposed molecular anion. This associative attachment (AA) process is exclusively operative within a very narrow resonance right at threshold (zero electron energy). In addition, a variety of negatively charged fragments are observed in the electron energy range 0–10 eV arising from dissociative electron attachment (DEA) processes. The observed DEA reactions include single bond cleavages (formation of NO2−), multiple bond cleavages (excision of CN−) as well as complex reactions associated with rearrangement in the transitory anion and formation of new molecules (loss of a neutral H2O unit). While any of these AA and DEA processes represent a reduction of the MISO molecule, the radicals formed in the course of the DEA reactions may play an important role in the action of MISO as radiosensitizer inside the hypoxic cell. The present results may thus reveal details of the molecular description of the action of MISO in hypoxic cells.

scholarly journals Low-energy electron driven processes in ices: Synthesis reactions and surface functionalization

2008 ◽  
Vol 6 (1) ◽  
pp. 89-98
Author(s):  
I. Martin ◽  
L. Amiaud ◽  
R. Azria ◽  
A. Lafosse
Keyword(s):  
Electron Energy ◽  
Electron Attachment ◽  
Low Energy ◽  
Energy Electron ◽  
Molecular Anions ◽  
Resolution Electron ◽  
Decarboxylation Reaction ◽  
Low Energy Electrons ◽  
Low Energy Electron ◽  
Substrate Surfaces

Low-energy electrons, and subexcitation energy electrons in particular, have the ability to induce efficiently chemical modifications within condensed molecular films and at substrate surfaces. By taking advantage of the Dissociative Electron Attachment (DEA) process, which leads to selective bond cleavages, the induced reactivity can be controlled solely by the electron energy. Two illustrative examples of induced reactivity and substrate functionalization achieved by low-energy electron processing of condensed molecules studied by means of High Resolution Electron Energy Loss Spectroscopy (HREELS) are reviewed, and special interest is given to the possibility of proposing overall reaction mechanisms. The resonant decarboxylation reaction in condensed films of trifluoroacetic acid CF3COOH induced by electrons at ~1 eV involves the formation of the transient species [CF3COOH]#- and the further formation of CO2 by a concerted mechanism. Diamond substrate functionalization by CH2CN organic groups through Cdiam-C and Cdiam-N bonds is performed by 2 eV electron irradiation of condensed acetonitrile CH3CN and involves reactants formed by DEA, that are neutral radicals H? and molecular anions [H2CCN]-.

Dissociation of methyl formate (HCOOCH3) molecules upon low-energy electron attachment

2018 ◽  
Vol 617 ◽  
pp. A102 ◽  
Author(s):  
L. Feketeová ◽  
A. Pelc ◽  
A. Ribar ◽  
S. E. Huber ◽  
S. Denifl
Keyword(s):  
Quantum Chemical Calculations ◽  
Electron Energy ◽  
Quantum Chemical ◽  
Methyl Formate ◽  
Experimental Studies ◽  
Electron Attachment ◽  
Low Energy ◽  
Energy Electron ◽  
Molecular Anion ◽  
Low Energy Electron

Context. The methyl formate molecule (HCOOCH3) is considered to be a key molecule in astrochemistry. The abundance of this molecule in space depends on the stability upon irradiation with particles like low-energy electrons. Aims. We have investigated the decomposition of the molecule upon electron capture in the electron energy range from about 0 eV up to 15 eV. All experimentally obtained fragmentation channels of the molecular anion were investigated by quantum chemical calculations. Methods. A high resolution electron monochromator coupled with quadrupole mass spectrometer was used for the present laboratory experiment. Quantum chemical calculations of the electron affinities of the generated fragments, the thermodynamic thresholds and the activation barriers for the associated reaction channels were carried out to complement the experimental studies. Results. Electron attachment is shown to be a purely dissociative process for this molecule and proceeds within two electron energy regions of about 1 eV to 4 eV and from 5 eV to 14 eV. In our experiment five anionic fragments with m/z (and possible stoichiometric structure) 59 (C2H3O2−), 58 (C2H2O2−), 45 (CHO2−) 31 (CH3O−), and 29 (CHO−) were detected. The most abundant anion fragments that are formed through dissociative electron attachment to methyl formate are the complementary anions CH3O− and CHO−, associated with the same single bond cleavage and different survival probability. Conclusions. The low-energy electron induced dissociation of methyl formate differs from its isomers acetic acid and glycolaldehyde, which leads to possible chemical selectivity in the chemical evolution.

Dissociation of the FEBID precursor cis-Pt(CO)2Cl2 driven by low-energy electrons

2020 ◽  
Vol 22 (11) ◽  
pp. 6100-6108 ◽  
Author(s):  
Filipe Ferreira da Silva ◽  
Rachel M. Thorman ◽  
Ragnar Bjornsson ◽  
Hang Lu ◽  
Lisa McElwee-White ◽  
...  
Keyword(s):  
Electron Attachment ◽  
Low Energy ◽  
Dissociative Electron Attachment ◽  
Low Energy Electrons ◽  
Theoretical Results

In this study, we present experimental and theoretical results on dissociative electron attachment and dissociative ionisation for the potential FEBID precursor cis-Pt(CO)2Cl2.

HgCl B2Σ+1/2 formation by low-energy electron impact dissociation of HgCl2 and(or) CH3HgCl molecules: applications to HgCl (B → X) laser

1990 ◽  
Vol 68 (2) ◽  
pp. 166-169 ◽  
Author(s):  
Mohammad F. Mahmood
Keyword(s):  
Energy Range ◽  
Electron Energy ◽  
Cross Sections ◽  
Band System ◽  
Low Energy ◽  
Dissociative Excitation ◽  
Intense Band ◽  
Electron Impact Dissociation ◽  
Low Energy Electrons ◽  
Low Energy Electron

An investigation was made of the process of dissociative excitation of a HgCl radical in the B2Σ+1/2 state due to collisions of low-energy electrons with HgCl2 and CH3HgCl molecules. Using the most intense band of the B2Σ+1/2 – X2Σ+1/2 system of the HgCl radical at 557 nm that corresponds to the ν′ = 0 to ν″ = 22 transition, emission cross sections were measured in the electron energy range 1–100 eV. The threshold electron energy for the observation of the B2Σ+1/2 – X2Σ+1/2 band system has been determined to be 7.0 and 8.0 eV for HgCl2 and CH3HgCl molecules, respectively.

Investigation of the Displacement Threshold of Si in 4H SiC

2006 ◽  
Vol 527-529 ◽  
pp. 481-484 ◽  
Author(s):  
W. Sullivan ◽  
John W. Steeds
Keyword(s):  
Electron Microscope ◽  
Low Temperature ◽  
Electron Energy ◽  
Transmission Electron Microscope ◽  
Low Energy ◽  
Electron Dose ◽  
Displacement Threshold ◽  
Transmission Electron ◽  
Low Energy Electrons ◽  
Low Temperature Photoluminescence

Samples of 4H SiC, both n- and p-doped, have been irradiated with low-energy electrons in a transmission electron microscope. The dependence of the silicon vacancy-related V1 ZPL doublet (~860nm) on electron energy and electron dose has been investigated by low temperature photoluminescence spectroscopy. Furthermore, this luminescence centre has been studied across a broad range of samples of various doping levels. Some annealing characteristics of this centre are reported.

scholarly journals Взаимодействие низкоэнергетических электронов с молекулами D-рибозы

2021 ◽  
Vol 129 (12) ◽  
pp. 1471
Author(s):  
И.В. Чернышова ◽  
Е.Э. Контрош ◽  
О.Б. Шпеник
Keyword(s):  
Total Cross Section ◽  
Energy Range ◽  
Cross Section ◽  
Electron Scattering ◽  
Cross Sections ◽  
Electron Attachment ◽  
Low Energy ◽  
Dissociative Electron Attachment ◽  
Low Energy Electrons ◽  
First Time

Abstract– The interactions of low-energy electrons (<20 eV) with D-ribose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of D-ribose molecules occurs effectively even at an electron energy close to zero. as well as in the energy range 5.50–9.50 eV. In the total cross section of electron scattering by molecules, resonance features at energies of 5.00–9.00 eV in the region of formation of ionic fragments C3H4O2–, C2H3O2–, OH–, associated with the destruction of molecular heterocycles, were experimentally discovered for the first time. The correlation of the features observed in the scattering and dissociative electron attachment cross sections is analyzed.

scholarly journals 5-Nitro-2,4-Dichloropyrimidine as an Universal Model for Low-Energy Electron Processes Relevant for Radiosensitization

2020 ◽  
Vol 21 (21) ◽  
pp. 8173
Author(s):  
Thomas F. M. Luxford ◽  
Stanislav A. Pshenichnyuk ◽  
Nail L. Asfandiarov ◽  
Tomáš Perečko ◽  
Martin Falk ◽  
...  
Keyword(s):  
Rational Design ◽  
Electron Attachment ◽  
Low Energy ◽  
Energy Electron ◽  
Model Molecule ◽  
Alternative Approach ◽  
Low Energy Electrons ◽  
Cluster Environment ◽  
Low Energy Electron ◽  
Low Solubility

We report experimental results of low-energy electron interactions with 5-nitro-2,4-dichloropyrimidine isolated in the gas phase and hydrated in a cluster environment. The molecule exhibits a very rare combination of many so far hypothesized low-energy electron induced mechanisms, which may be responsible for synergism in concurrent chemo-radiation therapy of cancer. In contrast to many previous efforts to design an ideal radiosensitizer based on one mode of action, the present model molecule presents an alternative approach, where several modes of action are combined. With respect to the processes induced by the low-energy electrons, this is not a trivial task because of strong bond specificity of the dissociative electron attachment reaction, as it is discussed in the present paper. Unfortunately, low solubility and high toxicity of the molecule, as obtained from preliminary MTT assay tests, do not enable further studies of its activity in real biological systems but it can advantageously serve as a model or a base for rational design of radiosensitizers.

scholarly journals Interactions of low-energy electrons with the FEBID precursor chromium hexacarbonyl (Cr(CO)6)

2017 ◽  
Vol 8 ◽  
pp. 2583-2590 ◽  
Author(s):  
Jusuf M Khreis ◽  
João Ameixa ◽  
Filipe Ferreira da Silva ◽  
Stephan Denifl
Keyword(s):  
Molecular Beam ◽  
Electron Attachment ◽  
Low Energy ◽  
Collision Induced Dissociation ◽  
Dissociative Electron Attachment ◽  
Low Energy Electrons ◽  
Singly Charged ◽  
Double Focusing ◽  
Doubly Charged ◽  
First Time

Interactions of low-energy electrons with the FEBID precursor Cr(CO)6 have been investigated in a crossed electron–molecular beam setup coupled with a double focusing mass spectrometer with reverse geometry. Dissociative electron attachment leads to the formation of a series of anions by the loss of CO ligand units. The bare chromium anion is formed by electron capture at an electron energy of about 9 eV. Metastable decays of Cr(CO)5 − into Cr(CO)4 −, Cr(CO)4 − into Cr(CO)3 − and Cr(CO)3 − into Cr(CO)2 − are discussed. Electron-induced dissociation at 70 eV impact energy was found to be in agreement with previous studies. A series of Cr(CO) n C+ (0 ≤ n ≤ 3) cations formed by C–O cleavage is described for the first time. The metastable decay of Cr(CO)6 + into Cr(CO)5 + and collision-induced dissociation leading to bare Cr+, are discussed. In addition, doubly charged cations were identified and the ration between doubly and singly charged fragments was determined and compared with previous studies, showing considerable differences.

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