SILAC Reagents and Sets
SILAC (stable isotope labeling by amino acids in cell culture) refers to labeling cultured cells with heavy amino acids for quantitative proteomic analysis. Labeling an entire proteome with heavy amino acids in vivo generates an ideal standard for quantitative proteomics. When a heavy labeled proteome is mixed with an unlabeled proteome then digested, every unlabeled peptide identified by the mass spectrometer can be quantified by its corresponding heavy peptide. In SILAC, the amino acids – arginine (Arg or R) and lysine (Lys or K) – contain heavy stable isotopes, so if digesting with trypsin, every peptide becomes isotopically labeled at the C-termini. This metabolic labeling strategy has been employed by hundreds of proteomic studies (see example references below). The advantage of metabolic labeling over in vitro tagging techniques is that the heavy and unlabeled samples are mixed before sample preparation, preventing variability between preparations from distorting the final quantitation results. This is especially important when extensive sample preparation (e.g. isolation of an organelle) is required.
CIL offers a myriad of free amino acids (either stable isotope-labeled or unlabeled) and its sets (i.e., labeled and unlabeled amino acids) for SILAC-MS proteomic studies. The stable isotopes that are to be metabolically incorporated can be conventional (e.g., L-Lys, L-Arg) or unconventional (e.g., L-azidohomoalanine) depending on the nature of the SILAC study. Quantitation of the standard or newly synthesized proteins is relative and can be performed in a targeted or nontargeted manner.
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SILAC Reagents and Sets