Anion transport through lipids in a hybrid bilayer membrane.

In this report, we use a hybrid bilayer membrane (HBM) as an electrochemical platform to study anion diffusion through a lipid monolayer. We first append lipid on a self-assembled monolayer (SAM) that contains a covalently bound Cu(I)/Cu(II) redox center. We then perform cyclic voltammetry (CV) using different anions in bulk solution and extract thermodynamic and kinetic information about anion transport. We analyze the results using linear combinations of fundamental chemical trends and determine that anion transport quantitatively correlates to polarity and basicity, a relationship we formalize as the lipid permeability parameter. In addition, we discuss how our findings can be interpreted according to the two leading mechanisms describing ion permeability through lipids. Our results demonstrate that anion transport in a HBM is best described by the solubility-diffusion mechanism, not the pore mechanism.