ELECTROSTATIC AND STRUCTURAL ALTERATIONS OF LIPID MONOLAYERS AND BILAYERS BY INTERACTION WITH VALINOMYCIN AND PHLORETIN

The structural and electrostatic effects of valinomycin and phloretin on phospholipid/cholesterol monolayers and bilayers were examined. Bilayer lipid membranes (BLMs) were studied exclusively by means of electrochemical potassium ion permeability experiments. Monolayer lipid membranes at an air-water interface were characterized by pressure-area curves, dipolar potential measurements and reflectance ellipsometry. The small biochemical molecules valinomycin and phloretin readily partitioned into the interior of BLMs but were excluded from the acyl chain region of compressed lipid monolayers. The electrostatic effects of phloretin were apparent and correlated well between monolayer and bilayer lipid membrane experiments. Significant alterations of the structure of the hydrophobic region of the monolayers were not induced by the electrostatic perturbations of phloretin.