Seven-step MudPIT. (A-G) The releasate from thrombin-activated platelets was digested with trypsin and the resulting peptides were separated using strong cation exchange and reverse-phase chromatography before introduction into an ion trap mass spectrometer. This figure displays the resulting chromatograms from the 2-dimensional-LC tandem MS. Chromatograms in panels A to G represent 7 successive salt elutions from an HPLC column. (H) A representative tandem MS spectrum is shown for a peptide from thrombospondin that was identified using SEQUEST.