Conformational analysis of phosphatidylethanol-amine in multilayers by infrared dichroism.

Built-up films of L-alpha-dipalmitoyl phosphatidylethanolamine were prepared. Infrared dichroism was measured for the sample and analysed by a new method. This method has been developed for the determination of the directions of transition moments in a film sample, in which there is an axis of symmetry of perpendicular to the film plane. The directions of transition moments were determined for the six vibrations assigned to the CH2 antisymmetric stretching, CH2 symmetric stretching, CH2 scissoring, C=O stretching, PO2- antisymmetric stretching, and C-C-N+ antisymmetric stretching modes. The results indicate that hydrocarbon chains are inclined at about 75 degrees to the film plane and the polar groups orient parallel to the plane in the builtup film. A structural model of the phosphatidylethanolamine in the built-up film is proposed.