An isotope-coded affinity tag (ICAT) is an in-vitroisotopic labeling method used for quantitative proteomics by mass spectrometry that uses chemical labeling reagents.[1][2][3] These chemical probes consist of three elements: a reactive group for labeling an amino acid side chain (e.g., iodoacetamide to modify cysteine residues), an isotopically coded linker, and a tag (e.g., biotin) for the affinity isolation of labeled proteins/peptides. The samples are combined and then separated through chromatography, then sent through a mass spectrometer to determine the mass-to-charge ratio between the proteins. Only cysteine containing peptides can be analysed. Since only cysteine containing peptides are analysed, often the post translational modification is lost.[4]
^Gygi SP, Rist B, Gerber SA, Turecek F, Gelb MH, Aebersold R (October 1999). "Quantitative analysis of complex protein mixtures using isotope-coded affinity tags". Nature Biotechnology. 17 (10): 994–9. doi:10.1038/13690. PMID10504701.
^US 6670194, Aebersold, Rudolf Hans; Gelb, Michael H. & Gygi, Steven P. et al., "Rapid quantitative analysis of proteins or protein function in complex mixtures", published 2003-12-30, assigned to University of Washington