Figure 3.

Chromatograms of the MRM signal intensities derived from the y₈ ions of the analyte decapeptides from tryptic digests of human serum showing no matrix interference with the y₈ ion of the analyte decapeptides from Stx1 and Stx2 subtypes. The signals corresponding to the y₈ ion of the analyte decapeptides from Stx1 (YNDDDTFTVK, YNDDDSFTVK, or YNDDDTFTAK); or Stx2a and Stx2f (YNEDDTFTVK); Stx2b, Stx2c, or Stx2d, (YNENDTFTVK); Stx2g (YNGDDTFTVK) or Stx2e (YNEDNTFTVK) are shown in each graph (i). Each sample was spiked with the corresponding ¹⁵N-labeled internal standard (ii). The signals for the y₈ ions from the corresponding ¹⁵N-labeled internal standards (ii) are normalized to 500 to allow the signal from the analyte decapeptide to be viewed on the same plot. The other signals are not normalized.