Scherfeld Dag, Kahya Nicoletta, Schwille Petra
Experimental Biophysics Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Biophys J. 2003 Dec;85(6):3758-68. doi: 10.1016/S0006-3495(03)74791-2.
In recent years, the implication of sphingomyelin in lipid raft formation has intensified the long sustained interest in this membrane lipid. Accumulating evidences show that cholesterol preferentially interacts with sphingomyelin, conferring specific physicochemical properties to the bilayer membrane. The molecular packing created by cholesterol and sphingomyelin, which presumably is one of the driving forces for lipid raft formation, is known in general to differ from that of cholesterol and phosphatidylcholine membranes. However, in many studies, saturated phosphatidylcholines are still considered as a model for sphingolipids. Here, we investigate the effect of cholesterol on mixtures of dioleoyl-phosphatidylcholine (DOPC) and dipalmitoyl-phosphatidylcholine (DPPC) or distearoyl-phosphatidylcholine (DSPC) and compare it to that on mixtures of DOPC and sphingomyelin analyzed in previous studies. Giant unilamellar vesicles prepared from ternary mixtures of various lipid compositions were imaged by confocal fluorescence microscopy and, within a certain range of sterol content, domain formation was observed. The assignment of distinct lipid phases and the molecular mobility in the membrane bilayer was investigated by fluorescence correlation spectroscopy. Cholesterol was shown to affect lipid dynamics in a similar way for DPPC and DSPC when the two phospholipids were combined with cholesterol in binary mixtures. However, the corresponding ternary mixtures exhibited different spatial lipid organization and dynamics. Finally, evidences of a weaker interaction of cholesterol with saturated phosphatidylcholines than with sphingomyelin (with matched chain length) are discussed.
近年来,鞘磷脂在脂筏形成中的作用增强了人们对这种膜脂长期以来的兴趣。越来越多的证据表明,胆固醇优先与鞘磷脂相互作用,赋予双层膜特定的物理化学性质。胆固醇和鞘磷脂形成的分子排列,大概是脂筏形成的驱动力之一,一般认为与胆固醇和磷脂酰胆碱膜的排列不同。然而,在许多研究中,饱和磷脂酰胆碱仍被视为鞘脂的模型。在这里,我们研究了胆固醇对二油酰磷脂酰胆碱(DOPC)和二棕榈酰磷脂酰胆碱(DPPC)或二硬脂酰磷脂酰胆碱(DSPC)混合物的影响,并将其与先前研究中分析的DOPC和鞘磷脂混合物的影响进行比较。由各种脂质组成的三元混合物制备的巨型单层囊泡通过共聚焦荧光显微镜成像,并且在一定范围内的甾醇含量下,观察到结构域形成。通过荧光相关光谱研究了膜双层中不同脂质相的归属和分子流动性。当两种磷脂与胆固醇以二元混合物形式结合时,胆固醇对DPPC和DSPC的脂质动力学影响方式相似。然而,相应的三元混合物表现出不同的空间脂质组织和动力学。最后,讨论了胆固醇与饱和磷脂酰胆碱的相互作用比与(链长匹配的)鞘磷脂弱的证据。