iTRAQ Reagents offer an isobaric “tagging” strategy for research into discovering and quantifying protein expression changes by mass spectrometry (MS) across multiple samples in studies ranging from biomarker discovery to disease analysis. By using the iTRAQ technology, researchers can improve overall protein and proteome coverage, simultaneously compare multiple samples, (i.e. normal versus diseased verses drug-treated or time course studies) in the same experiment; quantify, in absolute terms, specific proteins of interest, such as biomarkers, or screen drug targets, and increase statistical relevance. The reagents are isobaric, which confers the ability to run multiples of four or more samples in one experiment and where all four samples behave as one in separation chromatography and mass spec. This enables researchers to pull out low abundant marker proteins, because all signal in MS using iTRAQ is additive.