title: A comparison of the positive- and negative-ion mass spectra of bio-active peptides from the dorsal secretion of the Australian red tree frog, Litoria rubella.
abstract: The collision-induced tandem mass spectral data for MH+ and [M-H]- ions from six bio-active peptides from Litoria rubella are compared. Backbone cleavages of [M-H]- ions provide sequencing information for five of the peptides [e.g. Phe Pro Trp Leu (NH2) and pGlu Phe Pro Trp Leu (NH2)] and in these cases, the negative-ion spectra are as informative as the positive-ion spectra. Side-chain cleavages are also noted in these spectra. For example, (i) when Trp is present, the loss of C9H7N (129 u) competes with the backbone cleavages, and (ii) the [M-H]- ion of Ile Glu Phe Phe Thr (NH2) undergoes facile side-chain fragmentation [loss of H2O (from Glu) and MeCHO (from Thr)], but does not form any conventional backbone-cleavage ions.
authors: Department of Chemistry, University of Adelaide, South Australia, Australia.
authors: S T
authors: ST
authors: Steinborner
authors: J H
authors: JH
authors: Bowie
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001001:Anura / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis* / Q000737:chemistry; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D000596:Amino Acids; D010455:Peptides