Phospholipid polymers composition dependency

Bilayer composition can be almost infinitely varied by choice of the constituent lipids. Phosphatidylcholine (PC), a neutral phospholipid, has emerged as the major lipid component used in the preparation of pharmaceutical liposomes. Phosphatidylglycerol and phosphatidylethanolamine are also widely used. Liposomal bilayers may also accommodate sterols, glycolipids, organic acids and bases, hydrophilic polymers, antibodies and other agents, depending on the type of vesicle required. 

One interesting aspect of amphiphilic macromolecules is their interactions with phospholipid membranes, natural or artificial. Also amphiphilic in their chemical nature, phospholipid building blocks change their supramolecular ordering by incorporating amphiphilic polymers within their membrane assemblies. Depending on structural and compositional factors, various membrane deformations such as pore or tube formation, or complete disruption have been reported (34-40). In this respect, biological activities of amphiphilic... 

Diacetylenes in phospholipid bilayers have been the subject of extensive studies in our laboratory, not only because of the highly conjugated polymers they form, but also because of their ability to transform bilayers into interesting microstructures. Consequent to our synthesis and characterization of several isomeric diacetylenic phospholipids, we have found that the polymerization in diacetylenic bilayers is not complete. In order to achieve participation of all diacetylenic lipid monomer in the polymerization process, diacetylenic phospholipid was mixed with a spacer lipid, which contained similar number of methylenes as were between the ester linkage and the diacetylene of the polymerizable lipid. Depending upon the composition of the mixtures different morphologies, ranging from tubules to liposomes, have been observed. Polymerization efficiency has been found to be dependent on the composition of the two lipids and in all cases the polymerization was more rapid and efficient than the pure diacetylenic system. We present the results on the polymerization properties of the diacetylenic phosphatidylcholines in the presence of a spacer lipid which is an acetylene-terminated phosphatidylcholine. 

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