Binding of C1 mutant human rFVa₂ to soluble C6PS. The intrinsic fluorescence intensities of 0.2 μM of C1 mutant rFVa₂ in 50 mM Tris, 150 mM NaCl, 5 mM CaCl₂, 0.6% polyethylene glycol, pH 7.5, was measured as a function of C6PS concentration at 24°C to follow C6PS binding. The data were analyzed according to a simple binding model as described in “Binding of C6PS to human rFVa₂,” with results shown in Table 1. Error bars represent SEM.