Electroformation. The electroformation chamber and platinum electrodes were thoroughly cleaned before lipid films were dried on the electrodes. The chamber was first bath sonicated at 56 ˚C in a mixture of 7x detergent, ethanol and deionized water in a 1:3:3 ratio. The setup was then rinsed in deionized water for 20 minutes before being further bath sonicated in deionized water and rinsed again with deionized water for another 20 minutes. The chamber was then sonicated in ethanol at room temperature. After removing the chamber from the ethanol, the setup was dried immediately and kept in a desiccator until use. Films were formed by directly spreading 66nmol of lipid taken from a master stock onto the platinum electrodes. After spreading lipids on the electrodes, the chamber was kept in a desiccator overnight to remove residual chloroform. The chamber was then sealed with clean glass slides and vacuum grease. Once sealed, the chamber was filled with 1.5mL of submicron filtered and degassed 500mM sucrose Correlations between 2 H -/( 13 C -+ 12 C -) and C -/( 13 C -+ 12 C -) ratios for each lipid mixture. The 2 H -/( 13 C -+ 12 C -) ratio tracks the amount of 2 H-labeled lipid in the bilayer, while the 13 C -/( 13 C -+ 12 C -) ratio tracks the amount of before being heated to 65 ˚C. GUVs were electroformed at 10Hz, 3V (peak to peak) for 2 hours and then at 1 Hz, 3V for another 30 minutes.