FIGURE 6.

EIS of a tBLM and the effect of different ion size on the conductance of incorporated gramicidin channels. (A) EIS in a 100 mM KCl buffer of a DPTTC covered substrate before (circles) and after (squares) vesicle fusion, EIS in a 100 mM KCl/410 pM gramicidin buffer of the same bilayer (upward triangles) and EIS of the same bilayer after thorough rinsing with 100 mM tetramethylammoniumchloride (downward triangles). The data can be described using an equivalent circuit (Fig. 4 B). These fits yield in a bilayer resistance 540 kΩ cm², a reduced bilayer resistance of 13 kΩ cm² in the gramicidin buffer, and an increased bilayer resistance of 1.8 MΩ cm² after rinsing with tetramethylammoniumchloride. Only one fit (line) is shown, for clarity reasons. (B) Resistances from a different experiment from fits to EIS in 100 mM KCl are plotted for different gramicidin concentrations. Whereas the bilayer resistance varies >2 orders of magnitude, the capacitance remains almost constant at ∼780 nF cm⁻².