Figure 3.

Small angle x-ray scattering from BPTI in 50% D₂O, 1 M urea and 50 mM Na-phosphate, pH 7.0. (A) SAXS data were recorded and processed as described in the text and the legend to Fig. 1. The experimental data were fit to the scattering profile predicted from the crystal structure of BPTI (PDB entry 4pti), after numerically convolving the predicted profile with the beam profile. The dashed curves represent fits to the predicted form factor for BPTI, without incorporation of a structure factor. The solid curves represent fits to the BPTI form factor and the structure factor for a hard-sphere solution, with the fit parameters listed in Table 1. (B) The scattering intensities at zero angle were estimated by extrapolation of Guinier plots of numerically-desmeared data. The solid curve represents the fit of Eq. 7 to the experimental data, with a fixed value of the constant K = 5.2 cm²/g, and the fit sphere volume corresponding to a radius of 8.4 Å. The dashed curves are predicted from Eq. 7 using the same value of K and the indicated sphere radii. To see this figure in color, go online.