Fig. 6: Molecular dynamics simulation of Azo-SO₃H a lipid membrane.

a Molecular structure of the Azo-SO₃H isomers and snapshots of the E-isomer and Z-isomer inside the POPC membrane. The approximate position of the center of the membrane (z = 0) is shown by a dashed line. b Number densities of Azo-SO₃H as well as the POPC head group and the water molecules along the membrane normal (z-axis). The number densities for the POPC head group and water molecules were rescaled and multiplied by 0.017 and 0.01, respectively, so that all the profiles can be conveniently shown in one plot. The average value of the density profile of the POPC head group is shown by a dotted line. c The PMF profiles of the Azo-SO₃H molecules along the membrane normal are shown. The snapshot of the two isomers for the minimum of the free energy is represented. The PMF-profiles are shifted so that they agree at the average position of the POPC head group. The resulting distribution exp(-β PMF) for the two isomers is shown in the inset.