Figure 4. FXII-dependent activation of FXI, as measured by chromogenic assay in vitro, is not stimulated by misfolded protein aggregates.

Conversion of the chromogenic substrate Pefachrome XIa3371 in the presence of 1 nM FXII, 10 nM FXI, and 30 nM HK was measured. As a control, either FXII or FXI was omitted from the experiments. Although 2.5 μg/ml DXS-500k induced activation of FXIa in an FXII-dependent manner, as expected, misfolded protein aggregates of BSA-AGE (A), Hb-AGE (B), or FP13 (C) could not induce significant activation of FXI above buffer background at any concentration tested. Concentrations of these proteins up to 500 μg/ml were tested and found inactive (data not shown). The values in the graphs represent the mean ± SEM of duplicate determinations performed within 1 representative experiment of at least 3.