Figure 2

LC-MS/MS analysis of FN and TNC as extracted from cell culture plates treated with TEAB or PBS-only control. Shown are the FN peptide GNLLQCICTGNGRGEW native (a) and deamidated (b) forms as well as TNC peptide VEGYSGTAGDSMAYHNGR native (c) and deamidated (d) forms as identified by Mascot search of the MS/MS spectra. The percentage of deamidation of each targeted NGR motif was determined by integrating the area of the extracted ion chromatogram with +/− 5 ppm mass range of the calculated precursor masses of the native and deamidated peptides. TEAB-induced deamidation was 8% for FN and 5.3% for TNC, whereas only trace levels of protein deamidation were detected in the PBS-only control condition.