THE EFFECT OF PHLORETIN ON THE HYDRATION OF EGG PHOSPHATIDYLCHOLINE MULTILAYERS

The effect of phloretin on the hydration, structure and interactive pr operties of supported phospholipid bilayers has been studied by a comb ination of direct water adsorption measurements and X-ray diffraction. Adsorption isotherms show that over a wide range of relative vapor pr essures (from 0 to approximately 1.0) the addition of 20 or 40 mol% ph loretin significantly alters the amount of water adsorbed by egg phosp hatidylcholine (EPC) multilayers. X-ray diffraction analysis shows tha t the incorporation of phloretin decreases the width of the EPC bilaye r, thereby increasing the area per lipid molecule from approximately 6 4 Angstrom(2) for EPC to about 78 Angstrom(2) for EPC:Ph, 3:2, M:M. Ph loretin also decreases the distance between apposing EPC bilayers, mos t likely because it causes a reduction in repulsive hydration/steric p ressure between apposing bilayers. Because phloretin decreases the flu id layer between bilayers by a larger amount than it increases the are a per EPC molecule, phloretin has the effect of decreasing the water v olume in the multilayers. (C) 1997 Elsevier Science B.V.