(A-D): P188-GUVs. (E-H): PEG3000-PE-GUVs. (A, B, E, F) Leakage of Alexa 488, measured as a decrease in the relative fluorescence intensity, I/I0; (C, D, G, H) Change in relative diameter, D/D0, at Δπ = (A, C, E, G) 22±3, and (B, D, F, H) 45±5 mOsm as a function of time. The diameters of the examined GUVs are listed. (a). Possible lipid packing configurations in (I) GUV, (II) P188−GUV, and (III) PEG-PE−GUV.