The influence glutamic acid in protonated b₃ → b₂ formation from VGEIG and related analogs.

ABSTRACT: A direct pathway for the fragmentation of peptide b₃ fragment ions to b₂ ions has, until now, not been identified. Experimental evidence for the formation of a b₃ anhydride structure and isomerization to an extended macrocycle is demonstrated here by comparison of the completely different fragmentation patterns of the b₃ ions generated from protonated VGEIG and its methyl ester. In particular, the absence of a b₂ ion in the fragmentation spectrum of the methyl ester b₃ indicates that facile fragmentation of an anhydride-type b₃ is responsible for virtually all b₂ ions formed. The stability of this b₃ structure and the ease with which it fragments to the b₂ may be responsible for th

SUBMITTER: Morrison L 

PROVIDER: S-EPMC3647700 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature