Figure 4.

The effect of changing the hydrating salt cation in lipid systems of MO and DOPE. The effect of two concentrations - compared to water - of (a) CaCl₂ on the phase and lattice parameter of a MO:DOPE cubic phase; (b) LiCl on the phase and lattice parameter of a MO:DOPE cubic phase; (c) NaCl on the phase and lattice parameter of a MO: DOPE cubic phase. In the presence of Ca²⁺ ions, ${\mathrm{Q}}_{II}^D$ phases of monoolein and DOPE show little variation in lattice parameter before a phase transition to H_II. Upon hydration even with monovalent salt solutions, a complete ${\mathrm{Q}}_{II}^D$ to H_II phase transition is put off until the dominant force in the system is the membrane Gaussian curvature, with the system demonstrating phase coexistence at 18 mol% and 21 mol%. 1D SAXS patterns for the data are in the Supplementary Information, Figures S5–8.