FIG. 2.

Analytical ultracentrifugation. Curves were fit and residuals were determined as described in Materials and Methods. (A) Equilibrium sedimentation of VP4. Shown is the A₂₈₀-versus-radius plot of 453 μg of VP4 per ml in TNE following centrifugation at 9,000 rpm in an AN-60 Ti rotor (Beckman Coulter) at 4°C for 89 h. The curve, fit to data sets of VP4 centrifuged at starting concentrations of 112, 226, and 453 μg/ml, is the theoretical distribution of a 86.0-kDa particle with a partial specific volume of 0.7222 cm³/g in a buffer with a density of 1.005 g/ml using a baseline offset of 0.008 A₂₈₀ unit. (B) Velocity sedimentation of VP4. Shown are results of a second-moment analysis of the sedimentation of 865 μg of VP4 per ml in TNE at 4°C during centrifugation at 25,000 rpm. The fitted line has a slope of 3.3 s. (C) Equilibrium sedimentation of VP8CT. Shown is an A₂₈₀-versus-radius plot of 317 μg of VP8CT per ml in TNE following centrifugation at 20,000 rpm at 4°C for 45 h. The curve, fit to data sets of VP8CT centrifuged at starting concentrations of 79, 158, and 317 μg/ml, is the theoretical distribution of a 22.4-kDa particle with a partial specific volume of 0.7158 cm³/g in a buffer with a density of 1.005 g/ml using a baseline offset of −0.003 A₂₈₀ unit. (D) Equilibrium sedimentation of VP5CT. Shown is a A₂₈₀-versus-radius plot of 392 μg of VP5CT per ml in TNE following centrifugation at 9,000 rpm at 4°C for 90 h. The curve, fit to data sets of VP5CT centrifuged at starting concentrations of 98, 196, and 392 μg/ml, is the theoretical distribution of a 63.4-kDa particle with a partial specific volume of 0.7215 cm³/g that dimerizes with an association constant of 5.1 in a buffer with a density of 1.005 g/ml using a baseline offset of 0.002 A₂₈₀ unit.