ICAT: Isotope Coded Affinity tagging - ICAT is an in vitro labeling technique that modifies peptides or proteins specifically at the cysteine amino acid residue and can be used for accurate quantitation of protein expression.

Light ICAT label: The light ICAT reagent consists of a Cys-reactive group, an ICAT linker consisting of hydrogen atoms and a biotin tag. The chemically reactive group forms covalent bonds with peptides or proteins while the affinity tag enables the protein to be isolated by affinity chromatography in a single step.

Heavy ICAT label: The heavy ICAT label consists of a Cys-reactive group, an ICAT linker consisting of heavy deuterium isotope and a biotin tag.

Affinity purification: A chromatographic purification procedure that makes use of specific interactions between the analyte of interest and the capture reagent immobilized on the column. In ICAT, avidin affinity chromatography is employed due to its specificity of interaction with biotin.

ITRAQ: Isobaric Tagging for Relative and Absolute Quantitation - A technique used to quantify proteins by labeling N terminal residues with a tag.

SILAC: Stable Isotope labeling of Amino Acids in Cell culture - A technique of labeling proteins by providing tagged amino acids in cell culture, so that the cell take them up and label the proteins metabolically.