Figure 1. Schematic procedure for comprehensive identification and quantification of EGF-induced phosphoproteome based on SILAC technology.

Two populations of glioblastoma initiating cells were grown in media supplemented with normal (L-¹²C₆-lysine) and stable isotopes (L-¹³C₆-lysine), respectively. Each cell population is unstimulated or stimulated with 20 ng/ml EGF for 15 min, lysed, and combined in equal ratio. Phosphopeptides enriched through TiO₂ columns are subjected to mass spectrometric analysis.