Figure 5.

Analysis of the low-q SAXS data via Guinier fits. Quality of the fit is more obvious from the difference between the measured and fitted data, shown at the bottom of the panels. (A) Normal fit, monodisperse system. (B) Large aggregate in addition to the species of interest. The parameters of the Guinier fit within the truncated range and the resulting R_gyr and I(0) values are normal. (C) Polydisperse system. Note the upward curvature in the fit discrepancy throughout the entire low-q range. (D) Intrinsically unfolded protein. Note a similar upward curvature in the fit discrepancy throughout the entire low-q range. (E) The effect of a subtle inter-particle repulsion, only noticeable with the concentration series. All data were normalized to their concentrations. Note the absence of any systematic trends in the fit residuals. The presence of the structure factor is only noticeable from concentration dependence of the R_gyr and I(0)/c values. (F) The effect of a substantial inter-particle repulsion. Note the downward curvature in the fit discrepancy throughout the entire low-q range.