FIGURE 7.

SAXS measurements of PrP and Cu²⁺-bound PrP. A, scattering profiles of PrP (red circles) and Cu²⁺-bound PrP (blue circles) plotted against q (q = 4πsinθ/λ). Black traces are fitted lines obtained from P(r) distribution function. Differences in the scatter profiles of PrP and Cu²⁺-bound PrP are better seen in the linear plot (top right inset). Left bottom panel shows Guinier plots (ln(I(q)) versus q²) of PrP (red circle) and Cu²⁺-bound PrP (blue triangle). Straight lines show regions of the curve from where R_g values were calculated using Guinier plot. B, distance distribution function (P(r) function) of PrP (red trace) and Cu²⁺-bound PrP (blue trace). C, D_max; D, R_g distribution function calculated from the scattering profiles of PrP(23–231) (red trace in A) and Cu²⁺-bound PrP (blue trace in a) using the EOM method. In each (C and D), black traces show D_max (C) and R_g (D) distributions calculated from the pool of 10,000 conformations from PrP scattering profiles and green traces are from those of Cu²⁺-bound profiles. Red trace in each panel shows distribution from the selected 20 structures from PrP scattering profiles, and blue trace shows that of Cu²⁺-bound PrP. D, inset, EOM fitting of the PrP (black over blue trace) and Cu²⁺-bound PrP (black over red trace) with χ values of 0.778 and 0.775, respectively.