Curvature-driven lipid sorting occurs only close to a phase separation. (

*A*) Sorting of DHPE* to GM1* as a function of the reference curvature (Ref. curvature) for different lipid mixtures. For clarity, only 1 representative error bar is presented for the 0:0:100, 0:33:67, and 17:33:50 datasets. Data are binned over 4 points (

*n* = 12 vesicles for 30:35:35;

*n* = 10 for 0:0:100, 0:33:67, and

*n* = 7 for 17:33:50; error bars represent standard error of the mean). The horizontal line (sorting = 1), a guide to the eye, corresponds to the absence of sorting. (

*B*) Squared force

*f*^{2} vs. σ for typical 30:35:35 and 0:0:100 vesicles. A linear fit of

*f*^{2} vs. σ according to gives κ

_{v} = 15 ± 3

*k*_{B}*T* for the 0:0:100 composition. For the 30:35:35 composition, a clear deviation from linear behavior is observed. The line corresponds to a linear fit of the first 3 points. Error bars correspond to experimental precision. (

*C*) A linear fit to

*f*/

vs. σ according to gives a slope of 5.1 10

^{−6} m

^{3/2}.N

^{−1/2} for 30:35:35 and 0.2 10

^{−6} m

^{3/2}.N

^{−1/2} for 0:0:100. From the extrapolation to σ = 0, we find κ

_{v} = 38

*k*_{B}*T* for 30:35:35 and κ

_{v} = 15

*k*_{B}*T* for 0:0:100. Error bars correspond to experimental precision. (

*D*) Schematic phase diagram summarizing the evolution of sorting effect with membrane composition at

*T* = 22 ± 1 °C. The color scale illustrates the average slopes extracted from the linear fits to

*f*/

versus σ plots (see Table S1). Half-filled circles, compositions showing phase separation; black line, phase boundary deduced from our observations (

*SI Appendix*).

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