Enzymatic Labelling

The incorporation of two ¹⁸O atoms into each C-terminus of peptides derived from proteolytic digestion of biological samples has emerged as one of the leading global labelling strategies used in comparative quantitative proteomics. The success of the technique is due in part to the relative low cost of ¹⁸O water, the resulting +4 Dalton mass increase in molecular weight for the “heavy” peptide, and co-elution of ¹⁸O/¹⁶O peptide pairs from reverse-phase HPLC.