Considering polyplexes are typically formed at near-neutral pH and acidified during endocytosis in transfections, we also analyzed a third set of samples (pH 7.5-4.0, blue curves). These were initially condensed in 10 mM Tris-HCl buffer at pH 7.5, equilibrated for 1 hour, then transferred to a pH 4 acetate buffer solution and equilibrated for an additional 1 or 24 h before SAXS analysis.