[Relationship between the surface properties of phosphoglycerides and the structure of the phosphorus part of the...

Comparative studies have been made on surface properties of phospholipids with different chemical composition and different structure of the hydrophylic moiety of the molecule. Substitution of phosphoroyl oxygen by sulfur, as in diacetyl lecithins, makes thiolecithin molecules in monolayer more compact. In case of an analogous substitution of oxygen by sulfur in phosphodiglycerides, packing of molecules in a monolayer remains unaffected. It may be suggested that this fact is associated with different position of hydrophobic radicals in the compounds investigated. In contrast to classic neutral and phosphorus-containing phosphoglycerides, diolphospholipids form more condensed monolayers. It was shown that alpha- and beta-phosphatidic acids with the same composition exhibit identical surface activity. Incorporation of hydrophobic groups of aromatic type into synthetic phospholipid analogues increases surface activity, the effect being dependent on the location of these groups with the molecule.