Ion Mobility Spectrometry, Infrared Dissociation Spectroscopy, and ab Initio Computations toward Structural Characterization of the Deprotonated Leucine-Enkephalin Peptide Anion in the Gas Phase

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2014-09, Vol.118 (37), p.8453-8463
• Main Authors: Schinle, Florian, Jacob, Christoph R, Wolk, Arron B, Greisch, Jean-François, Vonderach, Matthias, Weis, Patrick, Hampe, Oliver, Johnson, Mark A, Kappes, Manfred M
• Format: Article
• Language: English
• Subjects: Enkephalin, Leucine - chemistry; Gases - chemistry; Hydrogen Bonding; Mass Spectrometry; Models, Molecular; Peptide Fragments - chemistry; Protein Conformation; Protons; Quantum Theory; Spectrophotometry, Infrared
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp501772d

Although the sequencing of protonated proteins and peptides with tandem mass spectrometry has blossomed into a powerful means of characterizing the proteome, much less effort has been directed at their deprotonated analogues, which can offer complementary sequence information. We present a unified approach to characterize the structure and intermolecular interactions present in the gas-phase pentapeptide leucine-enkephalin anion by several vibrational spectroscopy schemes as well as by ion-mobility spectrometry, all of which are analyzed with the help of quantum-chemical computations. The picture emerging from this study is that deprotonation takes place at the C terminus. In this configuration, the excess charge is stabilized by strong intramolecular hydrogen bonds to two backbone amide groups and thus provides a detailed picture of a potentially common charge accommodation motif in peptide anions.