With the aim of characterizing the permeabilization of the lipid membrane to ions, vesicles, by themselves or incubated with peptide, were mixed with the salt solutions and thereby subjected to an osmotic shock. A schematic illustration of the experimental method is presented in figure . Specific care was taken to minimize the risk of high local concentration variations and facilitate rapid mixing of the solutions. This was done by using stock solutions of twice the final concentration and mixing them in a 1:1 volume ratio. Hence, for both the static and time resolved experiments, we start with a LUV stock solution of 10 mg/mL. The vesicles are then diluted to 5 mg/mL, either with Tris buffer for the pure vesicles references, or with the appropriate peptide stock solution, so that a 1:1 volume ratio yields the appropriate PL ratio. The vesicles are incubated with peptide for approximately 30 minutes before they are mixed with salt, again in a 1:1 volume ratio. This yields a final vesicle concentration of 2.5 mg/mL, with or without peptide, and with or without salt. For the static SAXS measurements, all mixing was done manually using micropipettes and the samples were allowed to equilibrate for approximately 30 minutes after salt addition and before measurement. The samples measured here consisted of pure vesicles, as well as vesicles incubated with indolicidin in 1:20 PL ratio or LL-37 in 1:100 PL ratio respectively, measured at both 20 and 37 °C, and at four final salt concentrations of 0, 0.15, 0.30 and 0.60 M NaCl, respectively. The data are presented in figure .