PHASE FLUCTUATION IN PHOSPHOLIPID-MEMBRANES REVEALED BY LAURDAN FLUORESCENCE
PHASE FLUCTUATION IN PHOSPHOLIPID-MEMBRANES REVEALED BY LAURDAN FLUORESCENCE
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DOI：
10.1016/s0006-3495(90)82637-0
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发表时间：
1990-06-01
影响因子：
3.4
通讯作者：
GRATTON, E
中科院分区：
文献类型：
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作者：
PARASASSI, T;DE STASIO, G;GRATTON, E
膜蛋白周围的脂类组织可以影响它们的性质。我们用6-十二酰基-2-二甲氨基萘(Laurdan)研究了膜模型体系中的相共存和相相互转化。Laurdan的荧光性质为研究脂类结构域提供了独特的可能性，因为这种探针在凝胶和液晶相中具有不同的激发和发射光谱。激发光谱的不同使得Laurdan分子可以在两个相中的一个相中进行光选择。利用发射光谱的差异，就有可能观察到两相之间的相互转化。我们在不同温度下对二棕榈酰磷脂酰胆碱(DPPC)囊泡进行了实验，特别是在相变区域，在那里相共存和相之间的相互转化可能是最大的。我们还研究了不同脂类和双月桂酰磷脂酰胆碱(DLPC)、DPPC和50%DLPC混合物中的囊泡。收集了稳态荧光强度和偏振数据。为了量化相位共存和相互转换，我们引入了“广义极化”的概念。我们还进行了时间分辨实验，直接证明了相互转换过程。我们发现，在DLPC-DPPC混合物中，在20℃。C，位相转换发生在约30-40 ns内。
The organization of lipids surrounding membrane proteins can influence their properties. We have used 6-dodecanoyl-2-dimethylaminonaphthalene (Laurdan) to study phase coexistence and phase interconversion in membrane model systems. The fluoresence properties of Laurdan provide a unique possibility to study lipid domains because of the different excitation and emission spectra of this probe in the gel and in the liquid-crystalline phase. The difference in excitation spectra allows photoselection of Laurdan molecules in one of the two phases. Using the difference in emission spectra it is then possible to observe interconversion between the two phases. We have performed experiments in dipalmitoyl-phosphatidylcholine (DPPC) vesicles at different temperatures, in particular in the region of the phase transition, where phase coexistence and interconversion between phases is likely to be maximal. We have also studied vesicles of different lipids and mixtures dilauroylphosphatidylcholine (DLPC), DPPC, and 50% DLPC in DPPC. Both steady-state fluorescence intensity and polarization data have been collected. To quantitate phase coexistence and interconversion we have introduced the concept of "generalized polarization." We have also performed time-resolved experiments to directly prove the interconversion process. We have found that in DLPC-DPPC mixtures, at 20.degree. C, phase interconversion occurs in .apprx.30-40 ns.