A nomenclature system for labeling cyclic peptide fragments

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• Fragment ion analysis is crucial for characterizing cyclic peptides.
• Existing nomenclature systems can be complex and lack standardization.
• Cyclic peptides encompass diverse structures, including depsipeptides and modified amino acids.

Purpose of the Study:

• To propose a standardized nomenclature system for labeling fragment ions of cyclic peptides.
• To provide a systematic approach for describing ion structures derived from cyclic peptides.

Main Methods:

• Development of a four-part descriptor (xnJZ) for fragment ions.
• Definition of ion designations (a, b) and residue counts (n).
• Inclusion of N-terminal (J) and C-terminal (Z) residue codes for bond cleavage.

Main Results:

• The proposed nomenclature is applicable to various cyclic peptide types.
• It accommodates modified, unusual, and depsipeptide structures.
• The system is effective for gas-phase metal-ion cationized species.

Conclusions:

• The novel nomenclature system offers a clear and consistent method for fragment ion identification.
• This standardization facilitates the interpretation of mass spectrometry data for cyclic peptides.
• The system supports the structural elucidation of diverse cyclic peptide families.