Bond dissociation of the dipeptide dialanine and its derivative alanine anhydride induced by low energy electrons

Abstract

Dissociative electron attachment to dialanine and alanine anhydride has been studied in the gas phase utilizing a double focusing two sector field mass spectrometer. We show that low-energy electrons (i.e., electrons with kinetic energies from near zero up to 13 eV) attach to these molecules and subsequently dissociate to form a number of anionic fragments. Anion efficiency curves are recorded for the most abundant anions by measuring the ion yield as a function of the incident electron energy. The present experiments show that as for single amino acids (M), e.g., glycine, alanine, valine, and proline, the dehydrogenated closed shell anion (M-H) − is the most dominant reaction product. The interpretation of the experiments is aided by quantum chemical calculations based on density functional theory, by which the electrostatic potential and molecular orbitals are calculated and the initial electron attachment process prior to dissociation is investigated.

Transient Anions in Radiobiology and Radiotherapy: From Gaseous Biomolecules to Condensed Organic and Biomolecular Solids

“…Gas-phase investigations of LEE-induced damage to protein subunits have been reported for the amino acids alanine [115], tyrosine [116], glycine [117,118], proline [119,120], cysteine [121], and serine [122,123], as well as small peptides, such as dialanine [124] and amino acid esters [125]. For all cases, the anion yield functions (i.e., ion yields measured as a function of electron energy) exhibited localized maxima at energies below 15 eV, indicating the formation of TMAs.…”

Ab Initio Molecular Dynamics Simulation Study of Dissociative Electron Attachment to Dialanine Conformers

“…12 The fragments with masses of 87 (C 3 H 7 N 2 O) and 73 (C 3 H 5 O 2 ) would be produced by the C α -N 3 bond cleavage. In the DEA to dialanine, the anionic 4 fragments, m/z = 72, 87, and 88 with an intensity ratio about 80: 8: 1, were observed around 2 eV by Alizadeh et al; 9 while the additional fragment with m/z 73 was also observed, and the intensity ratio of the species with m/z of 72, 73, 87, and 88 was about 160: 5: 5: 1 determined by Muftakhov and Shchukin. 8 These anionic fragments were assigned as: C 3 H 4 O 2¯ (m/z=72), the isotopic ion of C 3 H 4 O 2¯ or C 3 H 5 O 2¯ (m/z=73), C 3 H 7 N 2 O¯ (m/z=87), and C 3 H 6 NO 2¯ (m/z=88).…”

“…[8][9][10][11][12][13] In the mass spectrometry experiments, various anionic fragments were observed, but their production mechanisms, in particular, for isobaric or nearly mass-equivalent fragments, were not well confirmed. [8][9][10][11][12][13] As shown in the molecular scheme (the upper panel) of Figure 1, it was believed that the C α -N 3 bond cleavage was preferred after the electron attachment to the local virtual orbital of the neighboring carbonyl group π*(C=O). 3,4,[8][9][10][11] The corresponding 2 Π* resonant state around 2~3 eV was frequently observed in the vertical electron attachment to organic molecules containing the C=O group.…”

“…[8][9][10][11][12][13] As shown in the molecular scheme (the upper panel) of Figure 1, it was believed that the C α -N 3 bond cleavage was preferred after the electron attachment to the local virtual orbital of the neighboring carbonyl group π*(C=O). 3,4,[8][9][10][11] The corresponding 2 Π* resonant state around 2~3 eV was frequently observed in the vertical electron attachment to organic molecules containing the C=O group. 12 The fragments with masses of 87 (C 3 H 7 N 2 O) and 73 (C 3 H 5 O 2 ) would be produced by the C α -N 3 bond cleavage.…”

Solvent effects on the structures and vibrational features of zwitterionic dipeptides: L-diglycine and L-dialanine

“…The first is present in hight concentrations in muscle and brain tissues, and the second is found in the skeletal muscle and brain of the mammals. L-diglycine (L-Gly-Gly) [3][4][5][6] and L-dialanine(L-Ala-Ala) [6][7][8] are the simplest dipeptides formed respectively with L-glycine [9] and L-alanine [10] amino acids.…”