Effect of Inserted Bacteriohopane-32-ol on the Stability of Liposomal Membranes

Bacteriohopane-32-ol (Monol), a hopanoid with one hydroxy group in the side chain, was prepared from hopanoids of Rhodopseudomonas palustris and incorporated into liposomal membrane composed of dipalmitoylphosphatidylcholine (DPPC). The effect of the inserted hopanoid on the stability of liposomes was compared with that of cholesterol (Cho) by measuring the release of 6-carboxyfluorescein (CF) entrapped in the liposomes. Monol has a stabilizing effect on liposomal membrane but its effect is different from that of Cho. Incorporation of Cho enhanced the stability of liposomes by increasing the contents. However, the incorporation of Monol at a low content of 20 mol% lowered, and that at higher contents increased, the stability. Furthermore, in the liposomes incorporated with Monol, there is no difference between the release of CF after incubation at 37°C and 45°C.