Figure 4.

Gramicidin increases the rate of lipid flip-flop in isotopically and compositionally asymmetric vesicles. The time evolution of the interleaflet distribution of POPC-d31 in s^∗LUVs (A) and DMPC-d54 in aLUVs (B) either without gA (black squares) or with gA at a gA/lipid ratio of 1:40 (red triangles), 1:100 (blue circles), and 1:200 (green diamonds). Both plots show the time-dependent changes in the distribution of POPC-31 between the outer and inner leaflets, relative to the first time point measured after vesicle preparation (ΔC). See text for details. Error bars represent SDs of at least three consecutive Pr³⁺ additions. Each time trace in (A) is from a single sample. The time traces of the compositionally asymmetric vesicles in (B) are from one (gA/lipid 1:40), two (no gA), and three (gA/lipid 1:200) separately prepared samples, respectively. The kinetics reported here corresponds to sample behavior at an ambient temperature of ∼22°C. To see this figure in color, go online.