一般認為生物細胞膜的結構存在著不同的脂質區塊，而這些區塊具有不同的化學成分，物理性質及功能。其中脂質浮排是一類富含膽固醇及抱合脂質的區塊，與許多重要的生物過程相關。過去在含有不飽和磷酯、飽和磷酯、及膽固醇三種混合物的模型細胞膜中已有許多重要研究結果，這些研究主要在幫助瞭解脂質浮排形成的作用力與機制。但其中有一未解且重要的課題是：在固定溫度下，POPC/DPPC/膽固醇 脂質膜展現單液態，但POPC/DPPC/麥角固醇 脂質膜卻展現lo及ld共存的雙液態。利用這個計畫，我們提出對POPC/DPPC/膽固醇_1-x麥角固醇_x的研究，透過研究不同膽固醇與麥角固醇的組成比例，可以知道這類系統在什麼條件下從單液態相變到雙液態，這對瞭解脂質浮排形成的作用力與機制助益良多。我們也會研究(POPC_1-x DOPC_x) /DPPC/膽固醇. 它在x=0的時候呈現單液態，而在x=1的時候呈現雙液態. 我們將會研究介於x=0和x=1之間的相行為. 然後建立這兩類脂質膜的溫度-成分之相圖. ;It is widely accepted that lipid domains with differing lipid/protein compositions, physical properties, and function exist in the membranes. Among them, the domains (lipid rafts) enriched in cholesterol and sphingolipid have been implicated to play important roles in a wide range of biological processes. Investigation of model membranes containing ternary mixtures of unsaturated phospholipid, saturated phospholipid, and sterol have been performed on various systems in order to understand the interactions governing the raft formation. One intriguing result is that while POPC/DPPC/cholesterol membranes display only one liquid phase, POPC/DPPC/ergosterol membranes display coexistence of lo and ld phases for a given temperature. Here we propose to study model membranes POPC/DPPC/(cholesterol_1-x ergosterol_x). By replacing cholesterol with ergosterol, we attempt to observe the evolution from one liquid to two liquid by varying the sterol composition. We will also study (POPC_1-x DOPC_x) /DPPC/cholesterol model membranes, which also exhibit one liquid (x=0) to two liquid transition (x=1) transition. We will explore the phase behavior between x=0 and x=1 region. In both cases, the temperature-composition phase diagrams will be established.
