Stable Isotope Labeling at the Peptide Level

Various alternatives to the ICAT and ICPL technologies have been reported but these methods are consistently based on chemical tagging at the peptide level. In this chapter, only the most common and promising peptide labeling approaches will be discussed (bill, 2003 Moritz and Meyer, 2003). 

Proteolytic peptide labeling with isotopes was first reported by Schnolzer et 

An inherent drawback of this methodology is that quantitative information is only obtained from those peptides which are subjected to MS/MS analysis. This fact stresses the necessity for efficient peptide separation via multidimensional chromatography (e.g., SCX/reversed-phase HPLC) prior to tandem MS analysis. Moreover, ion trap instruments cannot be employed in quantitative iTRAQ experiments since their peptide fragmentation spectra do not contain information 

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