515—Cation and anion responses of zwitterion phospholipid bilayers

Abstract

The electrochemical behavior of zwitterion phospholipid bilayers as determined with the help of membrane potential data, is examined. The synthetic DL-β,γ-dipalmitoyl-α-phosphatidylcoline bilayer shows at 30°C nernstian and sub-nernstian anion responses which depend on the cation present in the electrolytes (LiCl, NaCl, KCl, CsCl, CaCl 2, CeCl 3), and in some cases on the concentration of the solutions considered. On the other hand, nernstian cation responses have been observed in non-isothermal membrane-potential measurements performed on the same lipidic films. These experimental results are explained on the assumption that, from a potentiometric viewpoint the phospholipid membrane behaves as a neutral carrier membrane electrode. Accordingly, the form of the potential equations, and then the anion response of the bilayer, follows from the chemistry of the phospholipid molecules.