Figure 3.

Sedimentation–diffusion equilibrium of p1–30 and soluble IL-2Rβ. Profiles of absorbance versus radius from the center of rotation were obtained by sedimentation–diffusion equilibrium at 25 krpm in 20 mM sodium phosphate, pH 7.2, at 20°C. Residual errors as a function of radial distance from the center of rotation show the fitting quality of the data to the selected models. (A) p1–30 initial concentration was 150 μM. Absorbance was recorded at 242 nm. A better fit was obtained with a tetramer–octamer model of equilibrium (bottom) than with a tetramer model (top). (B) IL-2Rβ 31–230 initial concentration was 14 μM. Absorbance was recorded at 295 nm. An equilibrium monomer–dimer model (bottom) seemed slightly better than a dimer model (top). (C) p1–30Cys-FLC and IL-2Rβ 31–230 initial concentrations were 150 and 14 μM, respectively. Absorbance of p1–30Cys-FLC (at 490 nm) in the presence or absence of IL-2Rβ 31–230 is shown (top). Profile at 295 nm (aromatic residue absorbance of IL-2Rβ 31–230) of the peptide–protein mixture is also shown (bottom).