Practice question

Peptide backbone fragmentation nomenclature defined by Roepstorff and Fohlman categorizes ions based on broken bond position. Cleavage of the peptide bond between carbonyl carbon and amide nitrogen is the most labile linkage under low-energy collision-induced dissociation conditions. Retention of charge on N-terminal side generates b ions, while C-terminal retention produces complementary y ions. These paired series enable de novo sequencing and database searching for protein identification. Other cleavages such as Cα-carbonyl generate a/x ions and N-Cα generate c/z ions observed in electron capture dissociation, but collisional methods predominantly yield b and y ions.