title: The structure of gas-phase bradykinin fragment 1-5 (RPPGF) ions: an ion mobility spectrometry and H/D exchange ion-molecule reaction chemistry study.
abstract: Ion mobility-mass spectrometry (IM-MS) data is interpreted as evidence that gas-phase bradykinin fragment 1-5 (BK1-5, RPPGF) [M + H](+) ions exist as three distinct structural forms, and the relative abundances of the structural forms depend on the solvent used to prepare the matrix-assisted laser desorption ionization (MALDI) samples. Samples prepared from organic rich solvents (90% methanol/10% water) yield ions having an ion mobility arrival-time distribution (ATD) that is dominated by a single peak; conversely, samples prepared using mostly aqueous solvents (10% methanol/90% water) yield an ATD composed of three distinct peaks. The BK1-5 [M + H](+) ions were also studied by gas-phase hydrogen/deuterium (H/D) exchange ion-molecule reactions and this data supports our interpretation of the IM-MS data. Plausible structures for BK1-5 ions were generated by molecular dynamics (MD). Candidate MD-generated structures correlated to measured cross-sections suggest a compact conformer containing a beta-turn whereas a more extended, open form does not contain such an interaction. This study illustrates the importance of intra-molecular interactions in the stabilization of the gas-phase ions, and these results clearly illustrate that solution-phase parameters (i.e., MALDI sample preparation) greatly influence the structures of gas-phase ions.
authors.affiliation: Laboratory for Biological Mass Spectrometry, Department of Chemistry, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Holly A
authors.initials: HA
authors.lastname: Sawyer
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Marini
authors.forename: Earle G
authors.initials: EG
authors.lastname: Stone
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Ruotolo
authors.forename: Kent J
authors.initials: KJ
authors.lastname: Gillig
authors.forename: David H
authors.initials: DH
authors.lastname: Russell
mesh_terms: D001920:Bradykinin / Q000737:chemistry*; D019295:Computational Biology; D041961:Deuterium Exchange Measurement; D005740:Gases / Q000737:chemistry*; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry*; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D005740:Gases; D010446:Peptide Fragments; C079000:bradykinin (1-5); D001920:Bradykinin