title: Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling.
abstract: Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H](2-) ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H](3-) ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H](2-) ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H](3-) ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, 26506, USA.
authors.forename: Mahdiar
authors.initials: M
authors.lastname: Khakinejad
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, 26506, USA.
authors.forename: Samaneh Ghassabi
authors.initials: SG
authors.lastname: Kondalaji
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, 26506, USA.
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Donohoe
authors.affiliation: C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, 26506, USA. stephen.valentine@mail.wvu.edu.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Valentine
mesh_terms: D000595:Amino Acid Sequence; D000838:Anions / Q000737:chemistry; D003903:Deuterium / Q000737:chemistry; D041961:Deuterium Exchange Measurement / Q000379:methods; D006859:Hydrogen / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D056004:Molecular Dynamics Simulation; D010455:Peptides / Q000737:chemistry*
chemical_list: D000838:Anions; D010455:Peptides; D006859:Hydrogen; D003903:Deuterium
keywords: Hydrogen-deuterium exchange; Ion mobility spectrometry; Molecular dynamics simulations