Monolayer study of a new class of synthetic amino-etherlipids

Abstract

New amphiphilic molecules, synthetic aminolipids deriving step by step from phosphatidyl ethanolamine, are studied once spread into monolayers at the air/water interface. The successive modifications consist in replacing the phosphate group with one, two or three ethylene oxide units, reducing the carboxylic ester bonds on the glycerol into ethers and introducing the fatty chains in the 1,3-instead of 1,2-position on the glycerol. These structural modifications improve the chemical stability of the lipids that are subsequently much more easily purified and handled when compared to classical phospholipids. The resulting changes in the isothermal pressure-area curves are discussed in terms of those modifications and related to the nature and the composition of the aqueous phase. The monolayers appeared to be generally more expanded at a given surface pressure than with corresponding phospholipids. The introduction of ethylene oxide units in the structures increases the pressure at which the main phase transition occurs but surprisingly decreases the bulkiness of the molecules at the interface. Finally, the monolayers showed to be less sensitive to salt effects and pH variations when compared to phospholipid films.