1. Scattering from unilamellar vesicles. Small unilamellar vesicles of P2, PG2, and PG1Glc were prepared by extruding a multilamellar dispersion in Tris buffer through a 50 nm polycarbonate membrane filter. In the case of P1Glc, the lipid dispersion contained a significant amount of insoluble aggregates which could not be fully dispersed by bath sonication and those stuck to the membrane filters during extrusion. Therefore, the dispersion was subject to probe ultrasonication which helped to break down the larger aggregates. ~30 µL volumes of the vesicle dispersions were taken in 0.2 mL microtubes and loaded onto an automated sample loader at the beamline. Samples were exposed for a variable time (1s or 2s) and variable number of scans (24-50) were taken depending on the concentration of the lipids. Each sample was measured after storing at room temperature for up to a day and identical scattering profiles were obtained. Details of the SAXS data fitting is provided in the Supplementary Information ("Fitting of SAXS data from unilamellar vesicles" section).