The Effect of Valinomycin on the Electrical Properties of Solutions of Red Cell Lipids in n-Decane

This paper reports the electrical properties of thick lipid membranes in the absence and presence of valinomycin. The thick lipid membranes were formed by placing a solution of sheep red cell lipids in decane between two cellophane partitions which formed the interfaces between the membrane and the two aqueous bathing solutions. The DC electrical resistance of these structures was found to be directly proportional to the reciprocal of the concentration of lipids in the decane (C(L)). The limiting resistance, as (C(L) (-1)) approached zero, was 3 x 10(8) ohm-cm(2). Resistance was also found to be linearly related to membrane thickness. The limiting resistance at zero thickness was again 1–3 x 10(8) ohm-cm(2). These data are interpreted to indicate that the DC resistance of thick lipid membranes comprises two surface resistances (R(S)) at each interface with the aqueous bathing solutions, and a bulk resistance (R(B)) of the lipid-decane solution, arranged in series. Measurements of the effect of variations of area on resistance were consistent with this interpretation. Valinomycin reduced R(S) but had no effect on R(B). Under certain conditions, thick lipid membranes containing valinomycin behaved like highly selective K(+) electrodes.