The ternary mixture contains fluid DOPC, which explains the slightly larger coefficient below T co . Differential scanning calorimetry (DSC) is the tool of choice to detect phase transitions or more subtle molecular rearrangements. We performed such measurements on unilamellar vesicles for the binary and ternary mixtures (see Methods and SI). As shown in Figs. 4A, DSC detects broad peaks for the binary and ternary systems, and their maxima agree perfectly with our simulations (see labels in Fig. ). This suggests that a pure L o phase is present at Next, we verified that the membrane really shows L o -like rapid dynamics on both sides of T co . The characteristic rotational times of DPPC glycerol backbone are shown in Fig. . The rotational times are smaller than those of the gel phase, and decrease continuously upon heating by two orders of magnitude. They also agree reasonably well with those measured for the binary mixture at 285 K. The fluid-like nature can also be concluded by comparing lateral diffusion coefficients, shown in Fig. , with experimental data in different phases; The membranes are fluid, yet dynamics speed up significantly above T co . Additionally, we verified that the mean deuterium order parameters show L o -like high ordering at all studied temperatures (see Fig. ).