ICAT, SILAC, iTRAQ

TABLE 4.4. Proteomic Platforms Using Stable Isotopes 

Stable isotope Stable isotopes of an element differ in mass due to the number of neutrons but have the same elemental and chemical characterisitics as the element. Stable isotopes are not radioactive. Common stable elements and their stable isotopes are H and 2H 12C and BC 14N and 1SN O and lsO 32S and 34S. 

Element Number of protons within the nucleus of an atom. 

Atomic mass Number of protons and neutrons in the nucleus. 

Stable isotope proteomic platforms Peptides carrying different stable isotopes can be distinguished by high-resolution mass spectrometry, lamu can be resolved. ICAT, iTRAQ, and SILAC are examples. 

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The technique of isobaric tag for relative and absolute quantification (iTRAQ) is based on covalently labeling the amines at N-termini and the side chains of peptides with isotope-coded tags after the proteins have been isolated form biological systems, denatured, and enzymatically digested. Here the isotope labeling is carried out at a much later stage than in both SILAC and ICAT. iTRAQ is an MS/MS technique that uses CID-derived ions for both the identification and quantification of proteins. 

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