Quantification of proteins using isobaric labeling (tandem mass tag or TMT) starts with the reduction of disulfide bonds in proteins with Dithiothreitol (DTT). Alkylation with iodoacetamide (IAA) after cystine reduction results in the covalent addition of a carbamidomethyl group that prevents the formation of disulfide bonds. Then, overnight digestion of the proteins using trypsin or trypsin/LyC mixture, Tandem Mass Tag (TMT) labeling on Lysine residues, pooling of all samples and the fractionation of peptide mixture.