Fig. 6.

Use of cell lines as a spike-in SILAC standard. Knowledge of the overall similarities of the proteomes was used to construct a five cell line, heavy labeled “super-SILAC” reference standard. A, HeLa and K562 as well as Jurkat and K562 (B) proteins are sufficiently similar that most of the SILAC ratios are within a fivefold ratio above and below the one to one ratio. C, Quantification of the heavy super-SILAC mix consisting of five cell lines quantifies 96% of the K562 proteome within a fivefold ratio.