HPLC-ESI-MS of human plasma.

The NAPP-19 and QQET-30 peptides were unambiguously identified. Panel A: HPLC-ESI-MS total ion current (TIC) profile, with enlarged view (range 4.05–28.03 min) of the human sample (Panels B-D: extracted Ion Current (XIC) peaks corresponding to NAPP-19 (i.e. VGF485-503: B), its truncated co-eluting form VGF487-503 (C), and QQET-30 (D). The same panels indicate m/z values of the multiply charged ions used to extract the ion current peaks. Panel E: deconvoluted ESI-MS spectra of NAPP-19 (monoisotopic [M+H]+ at 1915.012 m/z) and VGF487-503 (monoisotopic [M+H]+ at 1729.932 m/z). Panel F: deconvoluted ESI-MS spectrum of QQET-30 (monoisotopic [M+H]+ at 3407.697 m/z). Sodium ion adducts are also depicted (ibidem). RT = retention time; NL = normalization level; amino acid numbering is referred to human VGF throughout.