Construction of Artificial Cell Membranes having Lipid Microdomains for Molecular Information Processing

Lipid microdomain formation in artificial cell membranes was investigated in relation to biologically important lipid rafts present in the cytoplasmic membranes. In order to imaging lipid microdomains, we developed a novel molecular sensor composed of a fluorescent auramine head, a hydrophobic cholesterol moiety, and a szlig-alanine unit connecting them. Fluorescence intensity of the molecular sensor was sensitive to microenvironmental viscosity. Thus, the molecule acted as an effective fluorescent sensor being capable of imaging lipid microdomains with different viscosities on giant liposomes. We also prepared an azobenzene-modified cholesterol derivative for photo-induced morphological changes in lipid bilayer membranes. Upon ultraviolet light irradiation, the cholesterol derivative embedded in a liposomal membrane with domain structures changed its conformation through photoisomerization of the azobenzene moiety to induce transformation of the lipid microdomain. Lipid microdomain formation was achieved not only in liposomes but also in the mixed lipid membranes formed with cerasome, which provided an effective platform for construction of artificial signal transduction systems.