FXIa cleavage of 6his-chem163S produces 6his-chem162R and 6his-chem158K. (A-B) Purified 6his-chem163S was incubated in assay buffer in the presence of 100 nM FXIa or 100 nM plasmin. Aliquots of reactions were removed every 5 minutes for 30 minutes, PPACK and ethylenediaminetetraacetic acid were added and analyzed by 6his-chem163S ELISA (A) or 6his-chem158K ELISA (B). Data points are the mean ± standard error of the mean from 3 independent experiments. (C-E) Purified 6his-chem163S was incubated with 30 nM FXIa for 0 minutes (C), 15 minutes (D), and 30 minutes (E) and analyzed by MALDI-TOF mass spectrometry. A representative experiment is shown. (F) The expected molecular weights of 6his-tagged chemerin forms were summarized to identify corresponding molecules in panels C-E.