Micro-domain growth in lipid membranes

In recent years, lateral lipid segregation in biological membranes so-called lipid raft gathers much attention because it is closely related to biological functions. Similar domains are observed in Giant Vesicles, which consist of ternary mixtures of cholesterol, saturated lipid (DPPC), and unsaturated lipid (DOPC) using a fluorescence microscopy. Below the miscibility temperature, liquid domains appear spontaneously from homogeneous membrane and they grow up by repeating collision and coalescence. In this study, we have investigated the initial stage of the micro domains using small uni-lamellar vesicles and a contrast matching technique of small angle neutron scattering. Above the miscibility temperature, lipids are mixed with a molecular level, thus we cannot observe intensity. However below the miscibility temperature, the micro domain growth starts and we can observe excess intensity due to the contrast between a domain and matrix. From the scattering functions, we obtained the information on the critical nucleus size of the micro domains.