我們使用氘核磁共振儀(2H NMR)研究由1，2-palmitoyl-sn-glycero-3-phosphocholine(DPPC)所組成，且含有高濃度(≧40mol%)麥角酯醇的人造細胞膜之物理性質。我們以氘取代DPPC在sn-1鏈上的氫，其光譜會隨著溫度及麥角酯醇的濃度(直到80mol%以上)而改變。當溫度高於相變溫度時，細胞膜呈現液晶有序相，我們發現不同的麥角酯醇濃度對DPPC長鏈部分的有序程度會有不同的影響：隨著麥角酯醇的濃度的增加到40mol%之前，長鏈的有序程度也跟著增加；一旦濃度達到50~80mol%，長鏈的有序程度卻隨濃度的增加而減少。在這兩個固醇濃度區間下，DPPC與麥角酯醇表現不同的交互作用。 膽固醇與麥角酯醇都會消弱DPPC在膠相與液晶無序相之間的相變，此兩種固醇分別都在低於相變溫度時減少DPPC的有序程度，而在高於相變溫度的時候增加DPPC的有序程度。然而無論在何種溫度範圍，麥角酯醇的作用比膽固醇的作用微弱。因此固醇在結構上的差異，對脂質與固醇間的交互作用有顯著的影響。此外固醇結構隨著溫度高於相變溫度或低於相變溫度，對DPPC碳鏈有序程度有不同的影響：固醇結構在溫度低於相變溫度時影響DPPC整條碳鏈的有序程度；然而在溫度高於相變溫的時候，僅影響C2-C12的有序程度。 We have studied the physical properties of 1,2-palmitoyl-sn-glycero-3- phosphocholine (DPPC) membranes containing high concentrations of ergosterol (≧40 mol%) using deuterium nuclear magnetic resonance (2H NMR). The sn-1 chain of DPPC was perdeuterated and spectra were taken as a function of temperature and ergosterol concentration up to 80mol%. It is striking that the DPPC chain order exhibit different ergosterol dependence at different ergosterol concentration ranges for a given temperature in the liquid-ordered phase. The chain order increases with increasing ergosterol up to 40 mol% erg, then decreases as ergosterol increases from 50 to 80 mol% at high temperature. DPPC interacts with ergosterol differently at these two ergosterol concentration ranges. Both ergosterol and cholesterol eliminate the phase transition between a gel phase and the ld phase of DPPC. They decrease and increase the order of DPPC below and above Tm, respectively. However, the effect of ergosterol is weaker than cholesterol. Therefore the structural difference in sterols has significant effect on the lipid-sterol interaction. Furthermore, the structural difference between ergosterol and cholesterol influences the DPPC chain differently below and above Tm. At temperatures below Tm, it affects the order of the whole DPPC chain. Above Tm, however, it only affects the order of C2-C12 segments of the DPPC chain.
