THIN-LAYERS OF PHOSPHOLIPIDS WITH BRANCHED CHAINS - THERMODYNAMIC ANALYSIS AND COMPARISON

Monolayers and bulk phases of glycerophosphocholines with a branched fatty acid chain in 2-position of the glycerol backbone were investigated. In the bulk the frustration caused by the drastic change of the molecule shape within the homologous series influences the structures of the gel and liquid-crystalline phases in a different way. Gel phases with interdigitated chains and non-bilayer liquid-crystalline phases were found. All of the lipids investigated form stable monolayers at the air/water interface. The analysis of the temperature dependence of the compression isotherms leads to the characteristic temperature T(c) (critical temperature of the monolayer). The comparison with the main-transition temperature T(m) of the bulk phases can be used as an indicator for structural differences between monolayers and bilayers.