Gas-phase chemistry of the negative ions of fully-protected peptides by high-resolution electrospray ionization tandem mass spectrometry

Eur. J. Mass Spectrom. 11, 403–408 (2005)
DOI: 10.1255/ejms.769

Gas-phase chemistry of the negative ions of fully-protected peptides by high-resolution electrospray ionization tandem mass spectrometry

Anna Napoli, Leonardo Di Donna, Giovanni Sindona^* and Elena Urso
Dipartimento di Chimica, Università della Calabria, via Pietro Bucci cubo 12/C, I-87030, Arcavacata di Rende (CS) – Italy

ABSTRACT:

Fully-protected C-terminal free peptides can be conveniently analyzed by high-resolution electrospray tandem mass spectrometry (ESI-MS/MS) in a quadrupole quadrupole time-of-flight tandem hybrid mass spectrometer, operated in the negative (–) ionization mode. The unusual choice of negative ions in mass spectrometry applications to peptide analysis was needed to obtain exhaustive sequence and structural data. The low-energy collision-induced dissociation (CID) experiments provided, in fact, tandem mass spectra displaying highly diagnostic fragments with a good signal-to-noise ratio. The method is applied to segments of porcine calcitonin (Cal), Cal (10–16, 1), Cal (17–24, 2) and Cal (25–28, 3) whose [M – H]^– deprotonated molecular ions provided low-energy CID mass spectra which allow the evaluation either of the primary structure of the peptide and of the location of the side-chain protective groups. ESI (+) MS can be conveniently used, in the high resolution mode, to achieve precise information on the elemental composition of the examined peptides.

Keywords: protected- peptides negative ions; calcitonin synthetic peptides negative ions; high resolution CID (–) of protected peptides; ESI/QqTof of protected peptides negative ions

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