The effect of salt addition is again entirely different when the vesicles have previously been incubated with AMPs. In figure , the corresponding kinetic data as in 3A are shown, but in this case for vesicles incubated with LL-37 in a 1:100 PL ratio. From the overlaid curves in the top left plot, we again see time dependent evolution of the scattering pattern. However, this time, the changes are almost exclusively observed at low Q. Unlike the peptide-free vesicles (Fig. ), there are no discernible shifts in the position of the minima, nor are there any oscillations indicative of deformation. The model analysis (fits shown with solid black lines) reveal that the observed changes at low Q are mainly due the gradual and time-dependent influx of NaCl into the vesicle interior. The resulting concentration of salt in the vesicle interior as a function of time is presented in figure . The LUVs with LL-37 at 1:100 PL ratio and measured at 20 °C displayed the slowest equilibration kinetics. However, even in this case, at the first time point of 7.8 ms, the internal salt concentration is already around 68 % (∼ 0.41 M) that of the external (0.60 M), and near complete equilibration is achieved after only 340 ms. When the membrane is in fluid phase at 37 °C, complete equilibration with the In figure , the corresponding kinetic data is presented for indolicidin and aurein. With figures 4A, 4B and 4C corresponding to vesicles incubated with indolicidin in 1:20 PL ratio, indolicidin in 1:50 PL ratio and aurein in a 1:20 PL ratio, respectively. All of these display more rapid equilibration than what was observed for LL-37 (Fig. ). While it takes approximately 90 ms for Indolicidin in 1:50 to reach near complete equilibration, at 1:20 PL ratio it takes only 24 ms. Interestingly, aurein, which inserts in a transmembrane fashion, displays even faster kinetics, with complete equilibration occurring before the first time point at 7.8 ms, despite the membrane being in gel phase. Here, the model analysis is done by sequential fitting of the kinetic frames, starting from the salt-free reference measured under otherwise identical conditions. With nominally no salt in the vesicle interior at t = 0, the internal salt concentration is fitted through the buffer fraction, f buf f (t) as presented in equation . Note that when f buf f = 1 the internal salt concentration is equal to the external.