Figure 2. Scheme of the Leiker-based CXMS workflow.
(A) Leiker contains a biotin moiety (magenta), a cleavage site (arrows), and six hydrogen atoms that are accessible to isotope labeling (asterisks). (B) The workflow for purification of Leiker-linked peptides. (C) Three types of Leiker-linked peptides. (D) Leiker-linked peptides generate a reporter ion of 122.06 m/z in HCD, as shown in the spectrum of an inter-linked peptide NYQEAKDAFLGSFLYEYSR-LAKEYEATLEECCAK (+4 charged, MH+ 4433.0553), in which C denotes carbamidomethylated cysteine.