Figure 6.

Partial ternary phase diagram of POPC/Chol/C16-GlcCer mixtures. (A and B) POPC/Chol/C16-GlcCer partial ternary phase diagrams at 24°C and (A) neutral and (B) acidic pH. The diagrams were determined using the photophysical properties of t-PnA and microscopy data. Solid symbols are experimental data for the following mixtures: POPC/Chol (gray triangles), POPC/GlcCer (black triangles), POPC/Chol/C16-GlcCer ternary systems with a constant POPC fraction (dark gray hexagons), and POPC/Chol/C16-GlcCer with a constant POPC/Chol ratio mimicking 25 (light gray circles) and 75 mol % of the l_o phase (black circles). The boundaries of the tie-triangle and the coexisting l_o+l_d phase are based on a mathematical analysis of the experimental data (see Table S2 and Supporting Material). The data for POPC/GlcCer were taken from Varela et al. (16), and the data for POPC/Chol mixtures were complemented by data from de Almeida et al. (29). The dashed lines on the right side of the ternary diagrams are just illustrative of the possible boundaries of the g+l_o phase. (C) Overlap of the diagrams shows a shift of the tie-triangle to higher GlcCer molar fractions at acidic pH (in gray) compared with neutral pH (in black). All of the lines have a strong experimental basis and are thermodynamically consistent.