The stopped-flow measurement sequences were repeated for each sample at least five times and the corresponding frames were averaged together, which significantly improved the signal-to-noise ratio. All frames were manually checked, and in the few instances where one frame indicated any artifact, it was removed before averaging. Mismatch of individual frames is likely due to the occurrence of bubbles in the exposed volume. As with the static measurements, the buffer scattering is subtracted from the vesicle scattering and the intensity normalized to absolute scale. For the kinetic measurements, a beam energy of 12.23 keV and a detector distance of 2.0 m were used, resulting in an experimental Q-range from approximately 4.3 • 10 -3 to 4.2 • 10 -1 Å-1 .