Voltammetric Behavior of the Transfer of Mono- and Polyammonium Ions across a Phospholipid Monolayer at the Nitrobenzene/Water Interface

Abstract

The influence of a phospholipid, dipalmitoyl phosphatidylcholine, layer at a nitrobenzenelwater interface on the transfer of tetraethylammonium ion and a polyammonium anti-fungus agent, poly[(dimethylimino)(2-oxo-1,2-ethanediyl)imino-l,6-hexanediylimino(l-oxo-l,2-ethanediyl)(dimethylimino)-l,6-hexanediyl] ion, across the interface was studied by normal pulse voltammetry. When the phospholipid was adsorbed to form a monolayer at the nitrobenzenelwater interface by its addition to the organic phase, the half-wave potential in the current vs. potential curves for the transfer of tetraethylammonium ion did not change, but the limiting current was significantly decreased at certain sampling times, indicating a retarding effect of the layer on the ion-transfer. On the other hand, in the current vs. potential curves for the transfer of the polyammonium ion, no significant change in either the half-wave potential or the limiting current was observed upon adding the phospholipid, indicating that the polyammonium ion can easily permeate through the phospholipid layer. The results suggest a new application of the voltammetric technique to the study of cell membrane permeability to polyionic bioactive compounds.