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. 2012 Apr 10;18(15):4613-9.
doi: 10.1002/chem.201102433. Epub 2012 Feb 28.

Formation and decay of the dehydrogenated parent anion upon electron attachment to dialanine

David Gschliesser  1 , Violaine Vizcaino, Michael Probst, Paul Scheier, Stephan Denifl
Affiliations

Formation and decay of the dehydrogenated parent anion upon electron attachment to dialanine

David Gschliesser et al. Chemistry. .

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.

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Figures

Figure 1
Figure 1
Molecular structure of dialanine.
Figure 2
Figure 2
Anion efficiency curve of the dehydrogenated parent anion [M−H]− for dialanine measured with the high-resolution electron monochromator (HEM; electron energy spread about 120 meV), two-sector-field mass spectrometer[23] (2SF-MS; electron energy spread about 1 eV), and in the inset for alanine[30] measured with the HEM. □=Dialanine (HEM); —=Dialanine (2SF-MS).
Figure 3
Figure 3
MIKE scan of the collision-induced decay (CID) of [M−H]− for dialanine formed at the initial electron energy of about 1 eV.
Figure 4
Figure 4
Trajectory for the loss of CO2 starting from [M−H]− dialanine isomer without hydrogen at the amide group (see text).
Figure 5
Figure 5
MIKE scan of the a) metastable decay and b) collision-induced decay (CID) of [M−H]− for dialanine formed at the electron energy of 5.5 eV.
See this image and copyright information in PMC

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