Workflow for ErbB2 targeted proteomics using multiprotease digestion and high resolution mass spectrometry quantitation. ErbB2 immunopurified from four 15 cm plates of untreated SK-BR-3 cells was pooled into a single sample. The sample was split into 12 aliquots and separated by SDS-PAGE. Triplicate in-gel digestion was performed using either trypsin, Asp-N, chymotrypsin, or a double digestion with trypsin plus Asp-N. Each sample was analyzed using an AB SCIEX TripleTOF 5600 mass spectrometer. Two approaches for high resolution LC-MS/MS quantitation were employed, MS1 Filtering and SWATH MS2 acquisition.