研究指出哺乳類的細胞膜上存在著擁有不同物理與化學特性的區塊(domain)，這些區塊被稱為脂質筏(raft)，脂質筏中含有高濃度的膽固醇。然而在酵母菌的細胞膜同樣發現脂質筏的存在，其中含有大量的麥角甾醇。而麥角甾醇在脂質筏上的作用，和膽固醇相似。為了更加了解脂質筏的行為，我們需要對脂質膜的相行為做研究。本文利用螢光顯微術和核磁共振(2H-NMR)來研究DPPC和POPE兩種脂質組成的人造膜，以及DPPC、POPE和麥角甾醇(ergosterol)所組成的人造膜的物理性質。螢光顯微術藉由螢光分子(NBD-DOPE)標示，便可觀察到螢光影像，以探討人造膜表面形態。核磁共振則藉由將氘取代DPPC 或 POPE sn-1上的氫，得以量測DPPC和POPE的相行為。結果顯示70:30 POPE/DPPC在15 度下，為兩種so相共存，其一為POPE-rich so 相，另一為DPPC-rich so 相，隨著飽和脂質DPPC的比例增加至50 mol%，POPE-rich so相消失，只剩下DPPC-rich so相。比較含有麥角甾醇以及未含有麥角甾醇的人造膜的結果。在70:30 DPPC/POPE，以及50:50 DPPC/POPE的人造細胞膜中加入固醇會產生lo相。最後我們總結不同比例的人造膜，並得到局部的相圖。 The specialized membrane microdomain was found in the mammalian cells membrane which termed lipid rafts with different physical and chemical properties. The lipid rafts contain 3 to 5-fold the amount of cholesterol found in the surrounding bilayer. Like cholesterol in mammalian cell membrane, ergosterol is important to the raft in the yeast cell membrane. To gain a better understanding of the effect of sterols on biological membrane properties requires investigations of the phase behavior. We study the physical properties of model membranes for binary mixture containing DPPC and POPE, and ternary mixtures containing DPPC, POPE and ergosterol using fluorescence microscopy and deuterium nuclear magnetic resonance (2H-NMR). The morphology of model membranes was observed as a function of temperature and composition by fluorescence microscopy. DPPC or POPE was deuterium labeled alternatively such that the phase behavior of both DPPC and POPE can be observed by 2H-NMR. 70:30 POPE/DPPC are in coexistence of 2 types of so phases at 15 ℃. As the DPPC concentration increases to 50 mol%, the POPE-rich so phase disappears and lipid bilayer only showed DPPC-rich so phase. The results of ternary mixtures containing sterol are compared with those of binary mixture to investigate the effect of sterol. In the 70:30 DPPC/POPE and 50:50 DPPC/POPE, ergosterol induces the formation of a lo phase in the so-phase bilayers. Finally, we present a partial phase diagram to summarize our findings.
