固醇對於生物膜的特性及功能具有重要的作用。大多數研究聚焦於含低濃度固醇的細胞膜。對於含高濃度固醇(30 mol%以上)的細胞膜的研究較少。有些細胞膜中的膽固醇的含量可以高達40 mol%以上，如老鼠的肝臟細胞、及達到50 mol%的紅血球細胞。因此我們有興趣了解高濃度固醇對脂質雙層膜的效應為何。我們利用核磁共振(2H NMR)與x-ray繞射對含有固醇的磷脂質兩元細胞膜的物理特性進行研究。我們氘化脂質分子sn-1碳氫鏈以利核磁共振(2H NMR)實驗的進行。我們在固定溫度下取得2H NMR光譜與x-ray散射圖隨著固醇濃度改變的實驗數據。我們觀察到在每個脂質/固醇系統中，碳氫鏈有序程度隨著固醇濃度的增加會而增加，且在特定的固醇濃度Cm1飽和。當固醇濃度大於Cx時，在膜處於液晶態下固醇會有溶解極限的產生。我們發現Cm1和Cx的值取決於固醇的種類，並推論這是固醇碳氫鏈上額外的分支阻礙了脂質與固醇間的交互作用所導致。;Sterols play important roles in the lateral organization of membrane. Most studies have been concentrated on membranes containing low sterol concentration (<30 mol %). However, less studies have been performed at the high sterol concentration regime (>30 mol %). It is found that cholesterol content can be as high as 40 mol % in rat liver cells and 50 mol% in red blood cells. The effect of high sterol concentration on the lipid bilayer is of interest. In this work, we have studied the physical properties of phospholipid model membranes containing various sterols using deuterium nuclear magnetic resonance (2H NMR) and x-ray diffraction (XRD). The sn-1 chain of the lipid molecule was predeuterated for the NMR experiment. NMR spectra and x-ray diffraction patterns were taken as a function of sterol concentration at fixed temperature. In each lipid/sterol system, the lipid chain order increases with increasing sterol concentration, then saturates at a specific sterol concentration Cm1. At a higher sterol concentration Cx, the sterol show solubility limit in the liquid-phase membranes. We found that the values of Cm1 and Cx depend on the type of sterol. It is suggested that a bulkier acyl chain of the sterol hinders the lipid-sterol interaction.
