Stable isotope labelling with amino acids in cell culture (SILAC)
SILAC relies on metabolic incorporation of amino acids into newly synthesised polypeptides. By using a combination of light (12C, 14N) and heavy (13C, 15N) amino acids in the culture of cells, samples can be mixed prior to protein enrichment and mass spectrometry analyses. The labelled peptides can be differentiated in the mass spectrometer to quantitate protein expression. Metabolic labelling avoids problems associated with missing labels that can occur using chemical labelling techniques. On the other hand SILAC is only applicable to live samples. Typical amino acids used for SILAC labelling include lysine and arginine.