Patent ID: 7109040

Claim:
A method for analyzing a peptide or peptides of interest, the method comprising: (a) fragmenting a first protein sample to form peptides therein; (b) fragmenting a second protein sample to form peptides therein; (c) labeling the peptides in the first protein sample with a first tag having the formula: A-B-C wherein: A is an amine-reactive group having a succinimide or maleimide moiety; B is a triazine moiety defining a first detectable isotope label; and C is a charge replacement group; (d) labeling the peptides in the second protein sample with a second tag having the formula: A-B-C wherein: A is an amine-reactive group having a succinimide or maleimide moiety; B is a triazine moiety defining a second detectable isotope label differing in mass from the first detectable isotope label; and C is a charge replacement group; (e) combining the labeled first and second protein samples and separating the peptide or peptides of interest from the combined first and second protein samples; and (f) determining the relative amount of the first detectable isotope label and the amount of the second detectable isotope label bound to the peptide or peptides of interest as a measure for analyzing the peptide or peptide of interest.