EIS studies of valinomycin-mediated K+ transport through supported lipid bilayers

Membranes capable of emulating biological systems were attached to gold electrodes via self-assembled monolayers (SAM) of mercaptopropionic acid molecules. The resulting supported bilayer lipid membranes (s-BLMs) doped with valinomycin were used to study the kinetics of K+ transport by electrochemical impedance spectroscopy in a wide frequency range and for varying K+-ion concentration in solution. Experimental data were modeled according to a set of fundamental microscopic equations describing the kinetic pathway for the K+/valinomycin system. The experimentally observed dependences of the membrane conductance on concentrations of the transported ion and the ionophore confirm the theoretical propositions. Derived values for the rate constants of association and dissociation of the permeating valinomycin–K+ complex agree with literature data.