Figure 4.

(A) SANS data for 1:1 dDPPC:DLPC 50 nm vesicles in contrast-matched solvent. For the 40.6 °C data, three curves are over imposed: a SASview [38] fit, which uses the analytical vesicle form factor, with both polydispersity and instrument smearing (dashed line); a MONSA calculation with all beads having the same ${\mathrm{SLD}}_{mean}$ (orange); and a fit with MONSA using two SLDs: ${\mathrm{SLD}}_{dDPP{C}_f}$ and ${\mathrm{SLD}}_{DLP{C}_f}$ (gray). The MONSA fits for data below the miscibility temperature use two SLDs: ${\mathrm{SLD}}_s$ and ${\mathrm{SLD}}_l$. The fits also satisfy the expected volume fraction for the solidus and liquidus phases (see Figures S8.1 and S8.2 in Section S8 of the Supplementary Information) as well as the molecular volume, given by densitometry and calorimetry (shown in (B)). (B) Molecular volumes derived from densitometry/calorimetry and those obtained from SANS fits. (C) Phase diagram shown in Figure 2 but including the solidus boundary extracted from the SANS fits constrained by the molecular volume—shown in (B)—and the expected solidus and liquidus volume fractions (Figures S8.1 and S8.2). Dashed lines delineate a fit to the solidus and liquidus boundary obtained using the approach by Van Dijck et al. [3]. The ideal liquidus boundary is shown with a black curve.