Figure 1.

Schematic work flow for quantitative phosphoproteomics. Steps performed in parallel with control or treated samples are indicated with four individual block arrows in white or grey/black. All procedures after the pooling (indicated with asterisk) of iTRAQ labelled peptides are indicated with a single broad multicoloured arrow. Phosphopeptides were isolated either from labelled and pooled samples (a) or from larger amounts of unlabelled samples, followed by iTRAQ labelling (b). Note that ion-exchange fractionation is required for sample deconvolution, desalting before IMAC and post-iTRAQ labelling sample clean-up, which means that two rounds of ion-exchange fractionation are necessary in (b).