Figure 3.

The hC3Nb2 binds multiple functional states of C3 with nanomolar affinity. hC3Nb2 was immobilized through a biotinylated C-terminal AviTag on a streptavidin-coated surface plasmon resonance flow sensor. The analyte was injected over the hC3Nb2-coated sensor at concentrations of 5, 10, 20, 30, or 60 nm C3 (A), C3b (B), or C3MA (C). D, summary of the SPR and BLI binding and rate constants. Binding and rate constants from SPR were determined using the BiaCore T200 evaluation software; n = 3 for C3 and C3b, n = 2 for C3MA. BLI binding curves are presented in Fig. S1. Binding and rate constants from BLI-based experiments were determined as described under “Experimental procedures”; n = 2 for murine C3b, n = 2 for human C3b. RU, response units. a.u., arbitrary units.