Fig 1.

Characterization of the FLIT peptide as a marker for 16E5. (A) Amino acid sequence of 16E5. The protein is cleaved by trypsin after the 2 arginine residues indicated in red, which generates 3 peptides, including C-terminal FLIT. (B) MRM shows breakdown of the parental FLIT ion (493.3 Da) to three major secondary ions during MS: IT (233.1 Da), FL (261.1 Da), and FLI (374.2 Da). (C) FLIT chromatogram showing all 3 transitions eluting at 24.9 min. MRM was performed on synthetic FLIT peptide that was eluted from a C₁₈ UPLC nanocolumn (15-cm length) with an increasing acetonitrile gradient.