Dissociation of the peptide bond in protonated peptides.

摘要: The dissociation of the amide (peptide) bond in protonated peptides, [M + H]+, is discussed terms structures and energetics resulting N-terminal bn C-terminal yn sequence ions. combined data provide strong evidence that proceeds with no reverse barriers through interconverting proton-bound complexes between segments emerging upon cleavage peptide bond. These contain part as a smaller linear (amino acid if one residue) either an oxazolone or cyclic (cyclic residue). Owing to higher thermodynamic stability but substantially lower gas-phase basicity peptides vs isomeric oxazolones, N-terminus cleaved when ionic (bn series) neutral (accompanying series). It demonstrated free energy correlations can be used derive thermochemical about In this context, dependence logarithm abundance ratio log[y1/b2], from GGX (G, glycine; X, varying amino acid) on X obtain first experimental estimate simplest b-type oxazolone, viz. 2-aminomethyl-5-oxazolone (b2 ion two glycyl residues). Copyright © 2000 John Wiley & Sons, Ltd.