Study on the phase transition behavior of polymerized liposomes through the interaction of diene-groups in their acyl chains

1, 2-Bis(2, 4-octadecadienoyl)-sn-glycero-3-phosphorylcholine (DODPC), which had a diene group in 2, 4-position of 1- and 2-acyl chains, was used to detect phase transition from shift of absorption maximum (λ_max) due to the change of interaction of diene groups. Selective polymerization of 1-acyl chains of DODPC with AIBN gave linear phospholipid polymers which had unreacted diene groups in 2-acyl chains. From the analysis of λ_max of thus selectively-polymerized liposomes, the phase transition behavior was detected clearly. We also studied the phase transition behavior of liposomes of which either layer of bilayer was selectively polymerized. Reconstitution of polymerized DODPC liposomes could also be evaluated from the temperature dependence of λ_max. The molecular packing of the polymeric liposomes was disturbed by reconstitution because of lower freedom of phospholipid polymers on reconstitution process.