Table 2.

Summary quantitative proteomics labeling techniques

Labeling Method		Stable isotope	Multi-plex analysis	Labeling target	Mass difference (Da)*	Relative cost	Ref.
Chemical labeling	ICAT	2H	2	Cys	8n	High	142
	GIST	2H or 13C	2	N-terminus & Lys	3(n+1) or 4(n+1)	Low	63, 146, 147
	18O	18O	2	C-terminus	2n	Medium	151, 152
	iTRAQ	13C, 18O, & 15N	4 or 8	N-terminus & Lys	114-117¥ 113-119 & 121£	High	153 - 162
Metabolic labeling	15N	15N	2	Labeled amino acids	variable	Medium
	SILAC	13C, 2H, and/or 15N	2, 3 or 5	Labeled amino acids	variable	Medium	132, 139-141

^*n = the number of labeled sites.

^¥reporter ions for 4-plex iTRAQ reagent.

^£reporter ions for 8-plex iTRAQ reagent.