Figure 1: Chromatogram of LC-MS/MS analysis of TiO2-enriched phosphopeptides from normal pancreatic duct and CFPAC-1 cells. Enriched phosphopeptides from each sample (1 mg) and 100 fmol standard peptide Ang I were loaded to C18 capillary column, and the eluted peptides were analyzed by LTQ-Orbitrap. The mass accuracy of Ang I and Ang II-Phos was within 5 ppm, and peak intensity of Ang I was ~ 1E8. For the normal duct sample, the retention time of exogenous control Ang II-Phos and Ang I were 78 min and 88 min, respectively, and the retention times of 3 internal control phosphopeptides (i.e. peak A, B, C) from AHNAK nucleoprotein isoform 1 were 50 min, 62 min and 98 min, respectively. Labeled peak A is the phosphopeptide LPSGSGAAS#PTGSAVDIR (2+ ion, m/z 861.9022); peak B is the phosphopeptide DIDISS#PEFK (2+ ion, m/z 615.7634); peak C is the phosphopeptide MYFPDVEFDIKS#PK (2+ ion, m/z 898.4021). These phosphopeptides were also identified in CFPAC-1 sample with similar retention times (± 2.0 min), indicating that the experimental procedure was reproducible and the MS results could be compared.