ABSTRACT
A phospholipid monolayer shares many properties with other insoluble monolayers. With modem experimental techniques, it can be studied directly without the need for much speculation. Perhaps the best explored are monolayers of glycerophospholipids with saturated aliphatic tails. Natural lipids are typical mixtures of phospholipids with different unsaturation and, sometimes, head group patterns. Isotherms, characteristic for such lipids, are typical for the LE phase. Notwithstanding this, phase separations might occur in such systems, as suggested by our knowledge with bilayers on the properties of defined mixtures for the case that one component prefers an ordered phase. Interaction of proteins and other water soluble compounds with the lipid environment has often been studied by measuring the monolayer isotherm. Control over the lipid monolayer structure is related to an understanding of domain formation. Interesting aspects of physics in two dimensions with local and global equilibrium properties emerge from this.
