Peptide toxin identification by liquid chromatography/mass spectrometry using an external electrospray ionization source combined with ion trap mass spectrometry

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Eur. J. Mass Spectrom. 6, 429 - 434 (2000)

Peptide toxin identification by liquid chromatography/mass spectrometry using an external electrospray ionization source combined with ion trap mass spectrometry

C. Afonso
Centre dÉtudes du Bouchet, BP 3, 91710 Vert-le-Petit and LCSOB, UMR 7613, Université Pierre & Marie Curie, Bat. F, boite 45, 4 place Jussieu, 75252 Paris, France
F. Modeste and P. Breton
Centre dÉtudes du Bouchet, BP 3, 91710 Vert-le-Petit, France
F. Fournier and J.C. Tabet
LCSOB, UMR 7613, Université Pierre & Marie Curie, Bat. F, boite 45, 4 place Jussieu, 75252 Paris, France E-mail:

ABSTRACT:

Three mutated synthetic peptides, analogs of the channel toxin BGK, were studied by liquid chromatography/mass spectrometryⁿ (LC/MSⁿ) using an external electrospray ionization (ESI) source. The reduction of disulfide bridges, combined with alkylation of the free cysteine residues, is shown to be a useful tool to determine their number as well as their location in conjunction with proteolysis of the peptides. The modified toxins were identified by LC/MS, while LC/MS/MS experiments were conducted to determine and locate modifications. Low-energy collision-induced dissociation spectra of S-alkyl cysteine derivative display ions (MH 91)⁺ attributed to the loss of HSCH₂CONH₂ as confirmed by sequential MS³ experiments. Identification and localization of cysteine residues can be achieved providing definitive identification for unknown proteins containing S-carbamidomethylcysteine.

Keywords: electrospray, resonant excitation, ion trap mass spectrometer, toxins, disulfide bridge

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