Probing Ionic Asymmetry in Artificial Membranes

Typically, the artificial membrane is exposed to symmetric ionic conditions, consisting of 150 mM NaCl, 2 mM CaCl₂, and 0.2 mM NaHCO₃. Once the membrane forms, each monolayer separates the volume of buffer into top and bottom, allowing for selective tuning of buffer composition. We use this feature to explore the effects of ionic asymmetry by adding 50 µL of 200 mM CaCl₂ to the top chamber. After each addition, we wait 5 min and compress the bilayer, as previously described. We repeat this process to further increase ionic asymmetry, while keeping the membrane intact.