Structure of the liposome composed of lipid-heme and phospholipids

The amphiphilic heme derivative, 5,10,15,20-tetra(α,α,α,α-o-(2′,2′-dimethyl-20′-(2′-trimethylammonioethyl) phosphonatoxyicosanamido)pheny)phorphinatoiron(II) (lipid-heme), formed a stable liposome (Φ ≈ 400 Å) with phospholipids. Differential scanning calorimetry showed that incorporation of the lipid-heme in the liposome bilayer (lipid/lipid-heme > 25) causes no disordering of the bilayer structure. Ligation of a bulky ligand to the lipid-heme liposome indicated that the lipid-heme situates facing predominantly outwards in the liposome. The closed vesicle structure and the stability of the lipid-heme liposome were also confirmed by the encapsulating capability of the fluorescence compound.