FIGURE 7.

Assembly and dissociation of C3bB(Mn²⁺) and C3bBb(Mn²⁺) on a C3b-coated biosensor surface. A, C3b (6747 response units (RU)) was covalently attached to a biosensor surface and treated for 60 s in succession with 1, 2, 5, and 10 μg/ml wild-type native factor B in Mn²⁺ HEPES buffer followed by buffer alone. Residual complexes were dissociated with EDTA HEPES buffer (indicated by the second bar). The resulting profiles were aligned at t = 0. The maximum peak of the C3bB(Mn²⁺) profiles represents complexes formed with 27% of the surface-bound C3b. B, the C3b-biosensor surface in A was treated for 60 s with 10 μg/ml wild-type native factor B in Mn²⁺ HEPES buffer followed by buffer alone. At ∼200 s the biosensor surface was treated for 60 s with 1.0 μg/ml factor D, 0.1 μg/ml factor D, or Mn²⁺ HEPES buffer alone. The resulting profiles were aligned at t = 0. C, the C3b biosensor surface in A was treated was treated for 90 s with 1 μg/ml factor B R234AV in Mn²⁺ HEPES buffer followed by buffer alone. At ∼300 s the biosensor surface was treated for 60 s with 1.0 μg/ml factor D. At ∼600 s the biosensor surface was treated for 60 s with EDTA HEPES buffer.