FIGURE 8.

(A) Factor X_a (0.6 μM) in buffer B (1.2 mM Tris, 150 mM NaCl, pH 7.4) was examined at 24°C in the presence of 3 mM CaCl₂ (solid line); and in the presence of 0.6 mM C6PS (dot-dash-dot line), C6PG (dotted line), and C6PC (dot-dot-dashed line) with 3 mM CaCl₂. (B) Factor X_a (0.6 μM) in buffer (1.2 mM Tris, 150 mM NaCl, pH 7.4) was examined at 24°C (solid line); and in the presence of 0.6 mM C6PS (dot-dash-dot line), C6PG (dotted line), and C6PC (dot-dot-dashed line) in the absence of CaCl₂. In the lower insets to A and B, the effects of C6PS (circles), C6PG (squares), and C6PC (triangles) concentrations on Θ₂₂₂/Θ₂₀₈ ratios measured from CD spectra of factor X_a in the presence of 3 mM Ca²⁺ (A) or in the absence of Ca²⁺ (B). The upper inset to A shows the variation of Θ₂₂₂/Θ₂₀₈ ratio with fraction of X_a present as dimer (obtained using k_dimer from the upper inset to Fig. 6 B) for factor X_a concentrations of 200, 300, and 600 nM.