FIGURE 1.

Characterization of an anti-uPA inhibitory nanobody. a, Nb4 or a control nanobody at the indicated concentration was incubated with uPA (0.25 nm) before adding plasminogen (100 nm) and the chromogenic plasmin substrate S-2251 (0.5 mm). The IC₅₀ value was calculated by non-linear regression. b, Nb4 or a control nanobody at the indicated concentration was incubated with uPA (2 nm) before addition of the chromogenic substrate CS-61(44) (47 μm). The inhibitory constant (K_i) was determined by non-linear regression. c, Nb4 (4 μm) were incubated with uPA-related trypsin-like serine proteases or uPA from other species. Chromogenic substrates were added to measure the effect of Nb4 on the amidolytic activity of the proteases. Error bars show the standard deviation from three experiments.