6533b870fe1ef96bd12cf971

RESEARCH PRODUCT

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Negatively charged lipid molecules were converted into polymerizable lipids by introduction of polymerizable mono- or bifunctional counterions. As an attempt to mimic the cytoskeleton of biomembranes, unsymmetrical polymeric vesicles were prepared, where the polyelectrolyte is attached either only to the inner or to the outer bilayer surfaces. Polymerizable cations were introduced to the outer surface of preformed small unilamellar vesicles via ion-exchange. The outer counterions of vesicles bearing polymerizable counterions at both sides of the membrane were replaced by Na+. Polymerization of these systems leads to unsymmetrical vesicles. The introduction, separation and polymerization of the organic counterions was monitored by UV-spectroscopy. Due to polymerization of the counterions, the phase transition temperature of the membranes is shifted remarkably to higher temperatures. For a comparison of ionically attached and covalently bound polymers, two cationic lipids were synthesized, which have a bifunctional polymerizable headgroup. In contrast to the lipids with “ionic” spacers, the polymerization of the covalently bound methacrylic units resulted in a decrease of the phase transition temperature. Thus, by application of ionically bound polymerizable units, unsymmetrical polymerized vesicle membranes are readily available. These systems may serve as models for mimicking the cytoskeleton of living cells.