Mattjus P, Slotte J P
Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
Chem Phys Lipids. 1996 Jun 17;81(1):69-80. doi: 10.1016/0009-3084(96)02535-2.
The objective of this work was to examine the interaction of cholesterol with both phosphatidylcholines, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and sphingomyelins, N-oleoyl-D-sphingomyelin (O-SPM) or N-palmitoyl-D-sphingomyelin (P-SPM), in monolayers at an air/water interface. We used cholesterol oxidase to probe for the relative strength of sterol-phospholipid interaction, and fluorescence microscopy to visualize lateral domain formation in the mixed monolayers. The ternary mixed monolayers, which contained cholesterol, POPC, and O-SPM had a twofold higher average oxidation rate than the corresponding system containing DPPC and P-SPM. This difference in oxidation rate between saturated and unsaturated systems was observed irrespective of the ratio between phosphatidylcholine and sphingomyelin in the monolayer. With either the saturated or the unsaturated systems, however, the rate of oxidation was influenced by the ratio of phosphatidylcholine to sphingomyelin. As the monolayer content of phosphatidylcholine increased and the sphingomyelin content decreased correspondingly (to maintain a constant cholesterol-to-phospholipid molar ratio), an increase in the average oxidation rate was seen in both saturated and mono-unsaturated monolayer systems. The relationship between the rate of cholesterol oxidation and the phosphatidylcholine/sphingomyelin ratio was not linear, suggesting a preferential interaction of cholesterol with sphingomyelin even when phosphatidylcholine was present in the monolayer. The formation and stability of cholesterol-rich lateral (liquid-condensed) domains in the monolayers, as determined by monolayer fluorescence microscopy, was found to be highly influenced by the phospholipid class, the degree of acyl chain saturation, and by the ratio of phosphatidylcholine to sphingomyelin in the monolayer. The differences in cholesterol oxidation rates and lateral domain formation, as a function of the ratio of two phospholipids in the monolayers, apparently derived from differences in the hydrophobic interactions between the lipids.
这项工作的目的是研究胆固醇与磷脂酰胆碱（1-棕榈酰-2-油酰基-sn-甘油-3-磷酸胆碱，即POPC，或1,2-二棕榈酰-sn-甘油-3-磷酸胆碱，即DPPC）以及鞘磷脂（N-油酰基-D-鞘磷脂，即O-SPM，或N-棕榈酰-D-鞘磷脂，即P-SPM）在空气/水界面单分子层中的相互作用。我们使用胆固醇氧化酶来探测甾醇-磷脂相互作用的相对强度，并使用荧光显微镜观察混合单分子层中侧向结构域的形成。含有胆固醇、POPC和O-SPM的三元混合单分子层的平均氧化速率比含有DPPC和P-SPM的相应体系高出两倍。无论单分子层中磷脂酰胆碱与鞘磷脂的比例如何，饱和与不饱和体系之间都观察到了这种氧化速率的差异。然而，对于饱和或不饱和体系，氧化速率都受磷脂酰胆碱与鞘磷脂比例的影响。随着单分子层中磷脂酰胆碱含量增加而鞘磷脂含量相应减少（以保持胆固醇与磷脂的恒定摩尔比），在饱和和单不饱和单分子层体系中均观察到平均氧化速率增加。胆固醇氧化速率与磷脂酰胆碱/鞘磷脂比例之间的关系不是线性的，这表明即使单分子层中存在磷脂酰胆碱，胆固醇与鞘磷脂之间也存在优先相互作用。通过单分子层荧光显微镜确定，单分子层中富含胆固醇的侧向（液态凝聚）结构域的形成和稳定性受到磷脂种类、酰基链饱和程度以及单分子层中磷脂酰胆碱与鞘磷脂比例的高度影响。单分子层中两种磷脂比例不同时，胆固醇氧化速率和侧向结构域形成的差异显然源于脂质之间疏水相互作用的差异。
