Resonant Electron Capture by Some Amino Acids and Their Methyl Esters

Vasil’ev, Yury V.; Figard, Benjamin J.; Voinov, Valery G.; Barofsky, Douglas F.; Deinzer, Max L.

doi:10.1021/ja058464q

Cited by 72 publications

(91 citation statements)

References 69 publications

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“…8,16 At 5-6 eV several additional peaks were present. Happily, the ions produced at these two energies are practically identical to those 17 obtained with the electron monochromator reflectron time-offlight mass spectrometer ͑EM-rToF-MS͒ ͑Ref.…”

Section: ͑M-h͒mentioning

confidence: 98%

Fragmentation of peptide negative molecular ions induced by resonance electron capture

Vasil’ev

Figard

Morré

et al. 2009

The Journal of Chemical Physics

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A simple robust method to study resonance gas-phase reactions between neutral peptides of low volatility and free electrons has been designed and implemented. Resonance electron capture ͑REC͒ experiments were performed by several neutral model peptides and two naturally occurring peptides. The assignment of negative ions ͑NIs͒ formed in these gas-phase reactions was based on high mass-resolving power experiments. From these accurate mass measurements, it was concluded that fragment NIs formed by low ͑1-2 eV͒ energy REC are of the same types as those observed in electron capture/transfer dissociation, where the positive charge is a factor. The main feature resulting from these REC experiments by peptides is the occurrence of z n − 1 ions, which are invariably of the highest abundances in the negative ion mass spectra of larger peptides. ͓M-H͔ − NIs presumably the carboxylate anion structure dominate the REC spectra of smaller peptides. There was no evidence for the occurrence of the complementary reaction, i.e., the formations of c n + 1 ions. Instead, c n ions arose without hydrogen/proton transfer albeit with lower abundances than that observed for z n − 1 ions. Only the amide forms of small peptides showed more abundant ion peaks for the c n ions than for the z n − 1 ions. The mechanisms for the N -C ␣ bond cleavage are discussed.

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Section: ͑M-h͒mentioning

confidence: 98%

Fragmentation of peptide negative molecular ions induced by resonance electron capture

Vasil’ev

Figard

Morré

et al. 2009

The Journal of Chemical Physics

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“…In proline, 21 the sum is only 0.05 of that for ͑Pro-H͒ − . A very recent study 44 of anion production in several amino acids and their methyl esters has been carried out using time of flight techniques for mass analysis. In principle this approach should be less susceptible to kinetic energy discrimination because of the pulsed injection of the ions.…”

Section: B Core-excited Resonancesmentioning

confidence: 99%

Total dissociative electron attachment cross sections of selected amino acids

Scheer

Możejko

Gallup

et al. 2007

The Journal of Chemical Physics

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Total dissociative electron attachment cross sections are presented for the amino acids, glycine, alanine, proline, phenylalanine, and tryptophan, at energies below the first ionization energy. Cross section magnitudes were determined by observation of positive ion production and normalization to ionization cross sections calculated using the binary-encounter-Bethe method. The prominent 1.2 eV feature in the cross sections of the amino acids and the closely related HCOOH molecule is widely attributed to the attachment into the -COOH * orbital. The authors discuss evidence that direct attachment to the lowest * orbital may instead be responsible. A close correlation between the energies of the core-excited anion states of glycine, alanine, and proline and the ionization energies of the neutral molecules is found. A prominent feature in the total dissociative electron attachment cross section of these compounds is absent in previous studies using mass analysis, suggesting that the missing fragment is energetic H − .

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“…The α-carbon atom of alanine is bound with a methyl group (see Figure 1). Dissociative electron attachment to gas phase alanine has been studied by Alfatooni et al [6], Ptasińska et al [7] and Vasil'ev et al [8]. However, to our knowledge, no experimental results concerning electron scattering (neither elastic nor inelastic) with gaseous alanine molecules have been published other than our results [9,10].…”

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Elastic scattering of electrons from alanine

Marinković¹,

Blanco²,

Šević³

et al. 2008

International Journal of Mass Spectrometry

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All remarks and questions put by referees were accepted and treated adequately. We are indebt to the referees for their comments and suggestions that improved a quality of the paper.The general quality of the figures was checked. Also the picture of alanine molecules was included in the manuscript. References were improved. The figure captions were made clearer. The Tables were checked and only at one point it was found the mismatch with the error value presented in Figure (this was value at 60 eV and 150 deg.). The error value in Table 1 was corrected.The relation between the inelastic cross section shown in previous Figure 2 and now Figure 3 and the absorption potential contribution Va(r) to the electron-atom interaction approximate optical potential was more clearly stated.We defined more explicitly few physical quantities: the f i () function of formula (4) & (6), and the dispersion functions evoked in the 2 nd § of the page 5.We discussed the dependence of the IAM approximation (p4) on the type of bond and on  delocalization of electrons.In the experimental part we have explained the procedure used for the calibration of the electron energy scale.We compared the absolute elastic cross sections of alanine to those of smaller organic systems such as THF and THFA. AbstractDifferential cross sections (DCSs) for elastic scattering of electrons from alanine, have been measured using a crossed beam system for incident energies between 20 eV and 80 eV and scattering angles from 10 o to 150 o . The experimental data were placed upon an absolute scale by normalisation to calculated absolute integral cross sections obtained using the corrected independent atom method incorporating an improved quasifree absorption model. The calculated data-set includes DCSs and integral elastic and inelastic cross sections in the incident energy range between 1 eV and 10000 eV. These theoretical results are found to agree very well with the experimental data both in the shape and magnitude of DCSs except at the smallest scattering angles.

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Resonant Electron Capture by Some Amino Acids and Their Methyl Esters

Cited by 72 publications

References 69 publications

Fragmentation of peptide negative molecular ions induced by resonance electron capture

Fragmentation of peptide negative molecular ions induced by resonance electron capture

Total dissociative electron attachment cross sections of selected amino acids

Elastic scattering of electrons from alanine

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