BICONTINUOUS CUBIC PHASE - A MODEL FOR INVESTIGATING THE EFFECTS ON ALIPID BILAYER DUE TO A FOREIGN SUBSTANCE

Biological effects of foreign substances are usually caused by their i nteraction within lipid bilayers with the membrane lipids. It is there fore desirable in many situations to determine the effects and the par tition of xenobiotic substances, as well as drugs, added to amphiphile -water systems. Bicontinuous cubic liquid crystals provide three-dimen sional isotropic matrices with symmetries easily obtained by X-ray dif fraction, and were shown to be a useful tool for an initial investigat ion of the molecular properties possessed by a foreign substance. The concept is illustrated by adding the transdermal penetration enhancer Atone(R) (n-dodecyl-caprolactam) to V-2-phases in the glycerol monoole ate (GMO)-water system. The weakly polar, water immiscible, Atone is k nown to favour reversed types of phases in liquid crystals. In the pre sent investigation, Atone was shown to prefer the lipid bilayer interi or, with about 19% anchored in the lipid-water interfacial region. Som e dependence of its location on water concentration was indicated. The unexpected swelling behaviour of monoacylglycerols in water (L(2) --> L(alpha) --> V-2) were postulated to result from the lipids changing their polar headgroup conformation, thus allowing for an increase in p acking parameter upon increasing the water content. Copyright (C) 1996 Elsevier Science Ireland Ltd