Peptide ion generated during the ionisation of peptides in an ion source or during tandem mass spectrometry of an intact protein in top-down proteomic analysis, selected for further analysis by means of tandem mass spectrometry.
Note: Once generated, a peptide fragment ion may become a precursor ion for tandem mass spectrometry of higher orders (\({\rm{MS}}^{n}\), \(n = 3\)).
Source:
PAC, 2018, 90, 1121. 'Terminology of bioanalytical methods (IUPAC Recommendations 2018)' on page 1159 (https://doi.org/10.1515/pac-2016-1120)