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. Author manuscript; available in PMC: 2011 Jan 1.
Published in final edited form as: Mass Spectrom Rev. 2010 Jan-Feb;29(1):79–125. doi: 10.1002/mas.20221

Figure 3.

Figure 3

The illustration of mass spectrometry-based targeted quantitative analysis to detect N-linked glycopeptides in body fluids. Synthetic peptides with stable isotope labeling are used as internal standards for the quantification of endogenous glycopeptides. As an example, N-linked glycopeptide AQLLQGLGFN*L#TER (Corticosteroid-binding globulin) was extracted from human serum with hydrazide chemistry-based solid-phase extraction and detected with an LC MALDI TOF/TOF platform with targeted approach. (Note: # indicates the amino acid that was stable isotope labeled (13C and 15N) in reference peptides; * indicates enzyme-catalyzed conversion of asparagines to aspartic acid at the site of carbohydrate attachment.)