Differential exoprotease activities confer tumor-specific serum peptidome patterns
J. Clin. Invest. Josep Villanueva, et al. 116:271 doi:10.1172/JCI26022 [Go to this article.]

Figure 4
MALDI-TOF/TOF MS/MS identification of serum peptide 2305. 0 as a fragment of complement C4a. Peptides from a serum sample of a breast cancer patient were extracted and analyzed by MS and the ion of choice selected for MS/MS analysis, as described in Supplemental Methods. The fragment ion spectrum shown here was taken for a Mascot MS/MS ion search of the human segment of the NR database (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=Protein) and retrieved a sequence, GLEEELQFSLGSKINVKVGGNS ([MH]⁺ = 2305.19; Δ = 4 ppm), with a Mascot score of 38. b and y fragment ion series are indicated together with the limited sequences (arrows at top). Note that y ions originate at the C terminus and that the sequence therefore reads backwards (see direction of the arrows).