title: Positive and negative ion electrospray tandem mass spectrometry (ESI MS/MS) of Boc-protected peptides containing repeats of L-Ala-gamma4Caa/gamma4Caa-L-Ala: differentiation of some positional isomeric peptides.
abstract: High-resolution electrospray ionization (ESI) quadrupole time-of-flight and ion trap tandem mass spectrometry has been used to distinguish the positional isomers of a new class of N-blocked hybrid peptides containing repeats of the amino acids, L-Ala-gamma(4)Caa ((l))/gamma(4)Caa((l))-L-Ala [Caa((l)) = Carbo (lyxose) amino acid, derived from D-mannose]. Both MS/MS and MS(3) of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, Boc-group, and the side-chain. It is interesting to observe that the abundant y(n)(+) ions are formed when the corresponding amide -NH does not participate in the helical structures in solution phase and relatively low abundance y(n)(+) ions resulted when the amide -NH involves in the H-bonding. Thus, it was possible to identify the amide -NH hydrogens that participate in the helical structures through H-bonding in solution phase. Further, negative ion ESI MS/MS has also been found to be useful for differentiating these isomeric peptide acids.
authors.affiliation: National Center for Mass Spectrometry, Indian Institute of Chemical Technology, Hyderabad, India.
authors.forename: P Nagi
authors.initials: PN
authors.lastname: Reddy
authors.forename: R
authors.initials: R
authors.lastname: Srinivas
authors.forename: M Ravi
authors.initials: MR
authors.lastname: Kumar
authors.forename: G V M
authors.initials: GV
authors.lastname: Sharma
authors.forename: Vivekanand B
authors.initials: VB
authors.lastname: Jadhav
mesh_terms: D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry
chemical_list: D010455:Peptides