Host-defence skin peptides of the Australian Common Froglet Crinia signifera:: sequence determination using positive and negative ion electrospray mass spectra

The amino acid sequences of seven signiferin peptides are provided by consideration of tandem mass spectrometric (MS/MS) data for the respective MH+ and [M-H](-) precursor ions. These methods do not differentiate between isomeric residues Leu and Ile; these were identified using the Edman degradation technique. The sequence of signiferin 1, a new smooth muscle contracting neuropeptide (RLCIPYIIPC-OH) containing a disulfide bridge, is best determined using the collision-induced dissociation (CID) spectrum of the [M-H](-) anion. The initial fragmentation of this system involves loss of H2S2, which furnishes an open-chain system that is readily sequenced using the alpha and P backbone cleavage anions. Copyright (C) 2004 John Wiley Sons, Ltd.