The fragmented ions produced by precursor ions were determined by the sequence of the marker peptide, so the averaged MS/MS spectra obtained around this retention time gave a perfect agreement with the peptide pattern, even without knowledge of sequence of the marker peptides.
Five same samples were digested in the same condition; the marker peptides in these five same samples could be detected; the selected ions chromatograms for the five samples from the family Equidae are shown in Figure 1.
1E, lanes a and b) and a 1783.9-Da marker peptide
([beta]66)NVLGAFSDGLAHLDNL, which was identified by its characteristic [2.sup.+] mass (m/z 892.9) at a retention time of 83.6 min (Fig.
The researchers extract a list of marker peptides specific to each species.
The test focuses on several distinctive marker peptides which, due to the amino acid sequence differences, are characteristic of either buffalo or cow.