Packing effects on polymerization of diacetylene lipids in liposomes and monolayers matrices
Year: 2016
Journal: Polym. J.
Authors: Baek, S; Phan, MD; Lee, J; Shin, K
Polymerization of 1,2-bis(tricosa-10,12-dinoyl)-sn-glycero-3-phosphocholine, DC8.9PC, which is a photo-polymerizable lipid, has been systematically investigated in various biological membrane-mimicking models as hosting matrices, for example, small unilamellar vesicles, giant unilamellar vesicles and Langmuir monolayers. In liposome systems, it has been observed that the photo-crosslinking (PCL) reaction between DC8.9PCs occurred only in gel phases composed of saturated lipids. No reaction was observed when DC8.9PCs were mixed with unsaturated lipids that intrinsically form a liquid phase, even when a high concentration of DC8.9PC was added. To explain how the existence of the gel phase-matrix induces polymerization, a mixed Langmuir monolayer system between DC8.9PC and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), where the lipid phases can be controlled, has been used. We found that the PCL reaction only occurred at liquid-condensed (LC) phases, and the reaction rates were strongly dependent on the packing states of the monolayers. Therefore, DC8.9PCs were possibly distributed in the LC domains of DPPCs, which consequently made the cross-distance between DC8.9PCs sufficiently small for the PCL reaction to proceed.
