Small-angle X-ray scattering analysis of CaHD, full-length LbpB, Lf, and the CaHD:Lf complex. From top to bottom, plots are as follows: SEC–MALS on a GE S200 increase 10/300, with molecular weight estimates shown above scattering peaks; raw SAXS scattering (log(I(s))); pairwise electron distribution function p(r); Kratky plot; Guinier plot. Raw scattering is the log-transformed intensity values from the detector. p(r) represents the fraction of electrons that lie within a distance r from another electron. The Kratky plot gives a qualitative measure of flexibility, with globular proteins exhibiting well-defined Gaussians and flexible proteins plateauing at higher scattering angles. The Guinier plot represents the low q-regions of scattering (smallest angles) and is used to estimate Rgyr as well as assess aggregation and particle repulsion.