FIGURE 6.
A, amino acid sequence with +1 and +2 ion identifications for the peptide containing a BES modification. Symbols, @, BES modification; #, iodoacetamide modification. All underlined ions were experimentally observed, whereas ions also in bold are those that allowed discrimination between assignment of the BES modification at Cys82 or Cys87; note that one of these discriminating ions (y2–22 at m/z 1274.1) is the most prominent ion in the spectrum. B, MS/MS spectra of the BES modified peptide. Inset, full MS spectrum at 95.47 min, with the arrow showing the [M + 3H]3+ BES-modified peptide at m/z 1168.4 that was automatically selected for MS/MS.