Next, we looked into lipid packing at both sides of T co in detail. We used the hexatic order parameter S hex of chosen in-plane atoms in the acyl chain region to characterize the degree of hexagonal packing. As shown in Fig. , DPPC shows relatively high S hex values in both mixtures until T co , above which they decay fast towards S hex of DOPC. The values in the binary system are slightly higher as DOPC is not perturbing its packing. DOPC itself is not involved in the hexagonally-packed clusters based on the lack of a crossover in its curve.