z-ion

https://doi.org/10.1351/goldbook.12614
Fragment ion containing the peptide \(\ce{C}\)-terminus formed upon dissociation of a peptide ion at the peptide backbone \(\ce{N-C}\) bond.
Source:
PAC, 2013, 85, 1515. (Definitions of terms relating to mass spectrometry (IUPAC Recommendations 2013)) on page 1600 [Terms] [Paper]