scholarly journals Experimental and Theoretical Studies of Dissociative Electron Attachment to Metabolites Oxaloacetic and Citric Acids

2021 ◽  
Vol 22 (14) ◽  
pp. 7676
Author(s):  
Janina Kopyra ◽  
Paulina Wierzbicka ◽  
Adrian Tulwin ◽  
Guillaume Thiam ◽  
Ilko Bald ◽  
...  

In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are observed peaking below 0.5 eV resulting in intense formation of fragment anions associated with a decomposition of the carboxyl groups. In addition, resonances at higher energies (3–9 eV) are observed exclusively from the decomposition of the oxaloacetic acid. These fragments are generated with considerably smaller intensities. The striking findings of our calculations indicate the different mechanism by which the near 0 eV electron is trapped by the precursor molecule to form the transitory negative ion prior to dissociation. For the oxaloacetic acid, the transitory anion arises from the capture of the electron directly into some valence states, while, for the citric acid, dipole- or multipole-bound states mediate the transition into the valence states. What is also of high importance is that both compounds while undergoing DEA reactions generate highly reactive neutral species that can lead to severe cell damage in a biological environment.

1971 ◽  
Vol 49 (9) ◽  
pp. 1571-1574 ◽  
Author(s):  
D. A. Rallis ◽  
J. M. Goodings

A trapped electron apparatus has been used to identify the processes involved in negative ion formation for the triatomic oxides SO2 and NO2. Two O− peaks are observed in SO2 with onset values at 4.2 ± 0.15 and 6.3 ± 0.2 eV, and peak values at 5.0 ± 0.15 and 7.4 ± 0.15 eV, respectively. From kinetic energy analysis of the O− ions, both peaks are found to have the same dissociation limit involving SO in its ground state. For NO2, two dissociative electron attachment peaks are observed with onset values at 1.6 ± 0.2 and 7.3 ± 0.3 eV, and peak values at 3.0 ± 0.2 and 8.1 ± 0.2 eV, respectively. The first broad peak is explained by overlapping contributions from two processes having the same dissociation limit involving ground state NO; they differ only in the amount of kinetic energy possessed by the fragments. The second peak appears to involve electronic excitation of the neutral fragment NO* with zero kinetic energy at onset.


RSC Advances ◽  
2014 ◽  
Vol 4 (63) ◽  
pp. 33222-33235 ◽  
Author(s):  
Benedikt Ómarsson ◽  
Sarah Engmann ◽  
Oddur Ingólfsson

Influence of fluorination on the negative ion resonances and dissociation dynamics in electron attachment to acetylacetone, trifluoroacetylacetone and hexafluoroacetylacetone are explored through calculations and experiments.


2020 ◽  
Vol 17 (167) ◽  
pp. 20200145 ◽  
Author(s):  
Helen F. Chappell ◽  
Ravin Jugdaohsingh ◽  
Jonathan J. Powell

Under physiological conditions, the predominant form of bioavailable silicon (Si) is orthosilicic acid (OSA). In this study, given Si's recognized positive effect on bone growth and integrity, we examined the chemical form and position of this natural Si source in the inorganic bone mineral hydroxyapatite (HA). X-ray diffraction (XRD) of rat tibia bone mineral showed that the mineral phase was similar to that of phase-pure HA. However, theoretical XRD patterns revealed that at the levels found in bone, the ‘Si effect’ would be virtually undetectable. Thus we used first principles density functional theory calculations to explore the energetic and geometric consequences of substituting OSA into a large HA model. Formation energy analysis revealed that OSA is not favourable as a neutral interstitial substitution but can be incorporated as a silicate ion substituting for a phosphate ion, suggesting that incorporation will only occur under specific conditions at the bone-remodelling interface and that dietary forms of Si will be metabolized to simpler chemical forms, specifically SiO 4 4 − . Furthermore, we show that this substitution, at the low silicate concentrations found in the biological environment, is likely to be a driver of calcium phosphate crystallization from an amorphous to a fully mineralized state.


2017 ◽  
Vol 8 (9) ◽  
pp. 5949-5952 ◽  
Author(s):  
Ragesh Kumar T P ◽  
Ragnar Bjornsson ◽  
Sven Barth ◽  
Oddur Ingólfsson

Dissociative electron attachment, 11 eV above the ionization energy of the focused electron beam induced deposition (FEBID) precursor HFeCo3(CO)12. A unique observation with potential significance for FEBID precursor design.


2008 ◽  
Vol 277 (1-3) ◽  
pp. 103-106 ◽  
Author(s):  
W. Barszczewska ◽  
J. Kočíšek ◽  
J. Skalný ◽  
V. Matejčík ◽  
Š. Matejčík

2011 ◽  
Vol 15 (07n08) ◽  
pp. 612-621 ◽  
Author(s):  
Pavlo V. Solntsev ◽  
Ben D. Neisen ◽  
Jared R. Sabin ◽  
Nikolay N. Gerasimchuk ◽  
Victor N. Nemykin

Reaction between H2TFcP (TFcP2- is a dianion of 5,10,15,20-tetraferrocenylporphyrin) with tin(II) chloride results in formation of the trans- Cl2SnTFcP complex, which was characterized by UV-vis, MCD, 1H and 13C NMR, and APCI MS methods. X-ray single crystal analysis was used to determine the structure of the target compound. Crystallography reveals a very unusual α,α,β,β-conformation of the ferrocene groups and largely planar structure of the porphyrin macrocycle. Density functional theory calculations predict that the HOMO in trans- Cl2SnTFcP is predominantly ferrocene centered, while LUMO is primarily localized over the porphyrin core. Redox properties of the trans- Cl2SnTFcP complex were investigated using electrochemical (CV and DPV), spectroelectrochemical, and chemical oxidation approaches. Electrochemical experiments conducted in low-polarity solvent using non-coordinating electrolyte reveal the sequential oxidation of ferrocene substituents along with porphyrin-based single-electron oxidation and reduction processes. The first ferrocene oxidation process is separated by 130 mV from the next three ferrocene based oxidations, which are more closely spaced. Mixed-valence [trans- Cl2SnTFcP]+ was generated in situ by spectroelectrochemical and chemical oxidation approaches and characterized by UV-vis-NIR spectroscopy.


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