Preparation and characterization of liposomes incorporating hydrophobic poly(amino acid)s with different secondary structure.

Incorporation of hydrophobic poly(amino acid) into liposomal membranes was achieved by the polymerization of N-carboxy anhydrides of amino acids in the egg yolk phosphatidylcholine (EyPC) bilayer under reduced pressure at 30 degrees C. The trapped volumes for the liposomes with and without polypeptides were 8.1-10.3 l mol-1 and 11.4 l mol-1, respectively. The permeability barrier abilities of liposomal membranes were lowered by the incorporation of polypeptides into the membrane bilayers. Water permeation across the membrane bilayer was more effective for the liposome with the alpha-helical polypeptide than for that with the beta-sheeted one.