Collision-Induced Dissociations of Deprotonated Peptides. Dipeptides Containing Asn, Arg and Lys

Abstract

The presence and position of Asn, Arg and Lys residues in dipeptides may be determined from a consideration of the collisional activation mass spectra of the (M-H)- ions formed by fast atom bombardment. All spectra show the basic dipeptide cleavage, i.e. NH₂CH(R¹)CONHCH(R²)CO₂^- → NH₂C(R¹)CONHCH(R²)CO₂H → NH₂C(R¹)=C=O + ^-NHCH(R²)CO₂H. There are a number of fragmentations characteristic of a particular α side chain: for example, Arg loses HN=C=NH (42 u).