Fig. 1.

Experimental approach. (A) Rat IMCD protein samples were digested with trypsin, followed by separation by strong cation exchange (SCX) chromatography. Phosphorylated peptides were enriched from total peptides by using IMAC. (B) Phosphopeptide samples were analyzed by LC-MSⁿ neutral loss scanning in which fragmentation of the phosphopeptide resulted in loss of phosphoric acid (−98 Da; neutral loss peak) from the full MS (parent ion) scan. This neutral loss peak was selected for further fragmentation and peptide identification in the MS³ spectrum.