A Multicoincidence Study of Fragmentation Dynamics in Collision of γ-Aminobutyric Acid with Low-Energy Ions

• Published in: Chemistry : a European journal Vol. 18; no. 30; pp. 9321 - 9332
• Main Authors: Capron, Michael, Díaz-Tendero, Sergio, Maclot, Sylvain, Domaracka, Alicja, Lattouf, Elie, Ławicki, Arkadiusz, Maisonny, Rémi, Chesnel, Jean-Yves, Méry, Alain, Poully, Jean-Christophe, Rangama, Jimmy, Adoui, Lamri, Martín, Fernando, Alcamí, Manuel, Rousseau, Patrick, Huber, Bernd A.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 23.07.2012; WILEY‐VCH Verlag; Wiley-VCH Verlag
• Subjects: amino acids; Carbon; Channels; Collision dynamics; density functional calculations; Fragmentation; Fragments; Gas phases; gas-phase reactions; ion-molecule reactions; mass spectrometry; Mathematical analysis; Physics; Quantum chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201103922

Fragmentation of the γ‐aminobutyric acid molecule (GABA, NH2(CH2)3COOH) following collisions with slow O6+ ions (v≈0.3 a.u.) was studied in the gas phase by a combined experimental and theoretical approach. In the experiments, a multicoincidence detection method was used to deduce the charge state of the GABA molecule before fragmentation. This is essential to unambiguously unravel the different fragmentation pathways. It was found that the molecular cations resulting from the collisions hardly survive the interaction and that the main dissociation channels correspond to formation of NH2CH2+, HCNH+, CH2CH2+, and COOH+ fragments. State‐of‐the‐art quantum chemistry calculations allow different fragmentation mechanisms to be proposed from analysis of the relevant minima and transition states on the computed potential‐energy surface. For example, the weak contribution at [M−18]+, where M is the mass of the parent ion, can be interpreted as resulting from H2O loss that follows molecular folding of the long carbon chain of the amino acid. Pure coincidence? A combination of mass spectrometric experiments with multicoincidence detection and quantum chemical calculations has been used to unravel the fragmentation mechanisms of the neuroinhibitor γ‐aminobutyric acid in the gas phase. Singly charged cyclic structures play an important role in the fragmentation, which preferentially takes place at the CβCγ bond (see figure).