title: Ion mobility-mass spectrometry applied to cyclic peptide analysis: conformational preferences of gramicidin S and linear analogs in the gas phase.
abstract: In this paper, we present an investigation of the gas-phase structural differences between cyclic and linear peptide ions by matrix-assisted laser desorption ionization-ion mobility-mass spectrometry. Specifically, data is shown for gramicidin S (cyclo-VOLFPVOLFP where phenylalanines are D rather than L-type amino acids and the O designates the non-standard amino acid ornithine) and five linear gramicidin S analogues. Results are interpreted as evidence for a beta-sheet (or beta-hairpin) conformational preference in both linear-protonated and sodiated-cyclic gramicidin S gas-phase peptides, and a preference for the protonated-cyclic peptide to adopt a collapsed, random coil-type conformation. A comparison with solution-phase circular dichroism measurements is performed, and structures similar to those observed in the gas phase appear to be favored in low-dielectric solvents such as 2,2,2-triflouroethanol. The utility of ion mobility-mass spectrometry (IM-MS) as a means of rapidly distinguishing between linear and cyclic peptide forms in also discussed.
authors.affiliation: Laboratory for Biological Mass Spectrometry, Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA.
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Ruotolo
authors.forename: Colby C
authors.initials: CC
authors.lastname: Tate
authors.forename: David H
authors.initials: DH
authors.lastname: Russell
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D005740:Gases / Q000737:chemistry*; D006096:Gramicidin / Q000032:analysis* / Q000737:chemistry*; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000032:analysis* / Q000737:chemistry*; D011487:Protein Conformation; D012680:Sensitivity and Specificity; D012997:Solvents / Q000737:chemistry
chemical_list: D005740:Gases; D010456:Peptides, Cyclic; D012997:Solvents; D006096:Gramicidin