近期的研究證據顯示，在生物膜中存在橫向異質的特性（lateral heterogeneities），這些異質的特性是指膜中有各種的脂質區塊(domain)，這些區塊中的脂質與蛋白質的組成成分及相關的物理特性都不同。這些脂質區塊，稱之為脂質浮排（lipid rafts），有高含量的膽固醇及抱合脂質(sphingolipids)且在許多生物過程中扮演重要的角色，不過，塊區的生成及相關的物理特性仍不太清楚。在含膽固醇的人造細胞膜中已被證實有液態有序(lo)及液態無序(ld)兩種液晶態區塊的存在，不只是膽固醇，其他的固醇也會使膜產生lo態。 我們運用氘核磁共振(2H NMR)光譜技術研究含有POPE和ergosterol兩種成分的人造細胞膜的相行為，我們藉核磁共振的光譜探測POPE膜，隨著ergosterol含量與溫度的改變，POPE膜中相的變化。研究發現，加入愈多的ergosterol，會使得膠態的POPE膜變的較無序；而會使得液晶態的POPE膜變的稍微有序。我們從核磁共振的光譜中可以得到POPE/ergosterol膜的部份相圖，當溫度小於Tm時，相圖顯示，有gel + lo 兩相共存的區域存在；當溫度大於Tm時，相圖顯示，POPE/ergosterol膜中只有一種液晶態存在。 Recent evidence suggests that lateral heterogeneities exist in biological membranes of living cell. The heterogeneity is proposed to be a coexistence of lipid domains with differing degrees of order, lipid/protein compositions, and physical properties in the membrane. Cholesterol and sphingolipid-enriched domains (lipid rafts) have been implicated to play important roles in a wide range of biological processes. However, their existence and physical properties have been controversial. Model membranes containing cholesterol show that two liquid crystalline phases: liquid-ordered (lo) and liquid-disordered (ld) phases coexist in some membranes. Not only cholesterol promote the formation of the lo phase, other sterols such as ergosterol also promote the formation of the lo phase. We investigate the phase behavior of POPE/ergosterol binary model membranes using solid-state deuterium nuclear magnetic resonance (2H NMR). The sn-1 chain of POPE was perdeuterated and NMR spectra were taken as a function of temperature and ergosterol concentration. It is found that adding ergosterol disorders the gel-phase POPE membranes, while only slightly orders the liquid crystalline–phase membranes. The partial phase diagram of POPE/ergosterol, constructed from the NMR spectra, exhibits gel + lo phase coexistence region below Tm. Above Tm, the membranes display only one single liquid crystalline phase.
