Electrochemical Investigation on Permeability of Organic Acid Ions Through Amphotericin B Channels

The influence of the channel-forming compound (amphotericin B) on the ion transport between two aqueous phases (W1 and W2) across the bilayer lipid membrane was electrochemically investigated. Sodium salts of organic acids (Na+Org−) were used as electrolytes in W1 and W2. When the concentrations of Na+Org− in W1 and W2 are asymmetrically different, the permeabilites of Na+ and Org− were estimated from the zero-current membrane potential. In the presence of amphotericin B, the permeability of Org− is larger than that of Na+. It is revealed that the permeability of Org− across the BLM decreases with an increase in molecular weight of Org−. The upper limit of molecular weight on the permeable anion was estimated to be about 230 by the extrapolation. The limit seems to be ascribed to the pore size of the amphotericin B channel.