title: Factors that influence helical preferences for singly charged gas-phase peptide ions: the effects of multiple potential charge-carrying sites.
abstract: Ion mobility-mass spectrometry is used to investigate the structure(s) of a series of model peptide [M + H](+) ions to better understand how intrinsic properties affect structure in low dielectric environments. The influence of peptide length, amino acid sequence, and composition on gas-phase structure is examined for a series of model peptides that have been previously studied in solution. Collision cross sections for the [M + H](+) ions of Ac-(AAKAA)(n)Y-NH(2) (n = 3-6) and Ac-Y(AEAAKA)(n)F-NH(2) (n = 2-5) are reported and correlated with candidate structures generated using molecular modeling techniques. The [M + H](+) ions of the AAKAA peptide series each exhibit a single, dominant ion mobility arrival time distribution (ATD) which correlates to partial helical structures, whereas the [M + H](+) ions of the AEAAKA ion series are composed of ATDs which correlate to charge-solvated globules (i.e., the charge is coordinated or solvated by polar peptide functional groups). These data raise numerous questions concerning intrinsic properties (amino acid sequence and composition as well as charge location) that dictate gas-phase peptide ion structure, which may reflect trends for peptide ion structure in low dielectric environments, such as transmembrane segments.
authors.affiliation: Department of Chemistry, Laboratory for Biological Mass Spectrometry, Texas A & M University, College Station, Texas 77843, USA.
authors.forename: Janel R
authors.initials: JR
authors.lastname: McLean
authors.forename: John A
authors.initials: JA
authors.lastname: McLean
authors.forename: Zhaoxiang
authors.initials: Z
authors.lastname: Wu
authors.forename: Christopher
authors.initials: C
authors.lastname: Becker
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Pérez
authors.forename: C Nick
authors.initials: CN
authors.lastname: Pace
authors.forename: J Martin
authors.initials: JM
authors.lastname: Scholtz
authors.forename: David H
authors.initials: DH
authors.lastname: Russell
mesh_terms: D000595:Amino Acid Sequence; D005740:Gases / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D005740:Gases; D007477:Ions; D010455:Peptides