Formation and Decay of the Dehydrogenated Parent Anion upon Electron Attachment to Dialanine

Abstract

The dehydrogenated parent anion [M−H]− is one of the most dominant anions formed in dissociative electron attachment to various small biomolecules like nucleobases and single amino acids. In the present study, we investigate the [M−H]− channel for the dipeptide dialanine by utilizing an electron monochromator and a two-sector-field mass spectrometer. At electron energies below 2 eV, the measured high-resolution ion-efficiency curve has a different shape to that for the single amino acid alanine, which is explained by the altered threshold energies for formation of [M−H]− determined in quantum chemical calculations. Moreover, the structure of the formed [M−H]− anion is further studied by investigating the unimolecular and collision-induced decay of this anion. Trajectory calculations have been carried out to aid the interpretation of the experimentally observed fragmentation patterns.

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

“…The relative contributions of the thermal conformers in gas phase are dependent on the vaporizing temperatures in the experiments, moreover, the DEA to the vibrational exited-state molecule is different from that to the ground-state target. The dissociations to the other fragments observed in the experiments, [8][9][10][11]13 in particular, those produced at the higher electron energies, are beyond the present investigation.…”

“…[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.…”

Electron scattering from molecules and molecular aggregates of biological relevance

“…Experimental studies of trialanine that used a high-energy resolution monochromator indicated that formation of anionic fragments is most abundant up to electron energies of ≈4 eV (Puschnigg et al 2014). Similar to the isolated monomer (Ptasińska, Denifl, Candori, Matejčík, Scheier & Märk 2005, Vasil'ev et al 2006, Abouaf 2008 and dimer (Muftakhov & Shchukin 2011a, Alizadeh et al 2011, Gschliesser et al 2012 of alanine, there is no evidence that a bound molecular anion exists on mass spectrometric detection timescales, and the dehydrogenated anion is one of the fragment anions observed. The thermochemical calculations performed on the threshold energies for formation of anionic products for trialanine showed a strong dependence on the tripeptide conformers, including internal hydrogen bonding of the carboxyl hydrogen with the oxygen of the adjacent amide group.…”

Electron-induced damage of biotin studied in the gas phase and in the condensed phase at a single-molecule level

“…Dissociative electron attachment (DEA) to DNA proceeds with high cross sections and can lead to the formation of single-and double-strand breaks [22][23][24]. LEE-induced bond breaking has thus received considerable attention and has been studied in a number of biologically relevant molecules, including amino acids [25][26][27], peptides [28,29], vitamins [30], DNA nucleobases [31][32][33], model compounds for the DNA backbone [34][35][36][37] and complete DNA nucleotides [38]. Here, we study LEE-induced damage of Bt in the gas phase by negative ion mass spectrometry, as well as in the condensed phase at the single-molecule level using AFM of DNA origami nanostructures [14].…”