Fluorescence Studies Of Biophysical Properties Of Polyun

神经细胞和视网膜组织的膜富含含有一条或两条长链多不饱和酰基链的磷脂。二十二碳六烯酸(DHA或22：6N-3)是这些组织中主要的多不饱和酰基链。本研究旨在确定多不饱和磷脂调节G蛋白偶联受体信号的分子基础，特别是那些含有22：6N-3酰基链的磷脂。研究还集中在这些磷脂对急性乙醇暴露的反应。荧光能量转移(FRET)研究表明，在含有di16：0pC和di22：6PC+胆固醇的双层中形成侧向结构域，这依赖于胆固醇和视紫红质的存在。继续进行FRET研究，以及原子力显微镜和差示扫描量热法，以表征含有脂类的22：6N-3双层中的横向结构域形成。酰链自由体积和曲率应力都被引用为双层性质，它们调节膜蛋白的功能。实验表明，这两种特性之间存在相反的关系，这表明它们在调节蛋白质功能方面可能具有相反的效果。最近的研究表明，膜蛋白功能的主要调节性质将取决于膜脂组成。胆固醇-鞘磷脂的相互作用被认为是生物膜中结构域或RAFT形成的驱动力。我们对di16：0pc-di22：6pc-胆固醇-人紫红质系统的研究表明，胆固醇-脂类相互作用是形成侧区结构域的更普遍的驱动力，蛋白质-脂类相互作用也可能是一个贡献因素。为了阐明磷脂组成在结构域形成中的作用，研究了胆固醇在确定的脂类组成的双层中的分配。建立了一种新的测定胆固醇在脂双层中的分配的方法。这些研究表明，胆固醇的分配是由磷脂头部基团和酰基链组成决定的。多不饱和酰基链在降低脂膜胆固醇水平方面是最有效的，而反式脂肪酸则增加膜胆固醇含量。这些研究对于开发和理解脂类成分和22：6N-3酰基链的作用，特别是在结构域形成、膜蛋白功能的调节、胆固醇在细胞膜中的异质性分布以及与多不饱和脂肪酸和反式脂肪酸相关的健康益处和缺陷方面具有重要意义。

The membranes of neuronal and retinal tissue are high in phospholipids containing one or two long chain polyunsaturated acyl chains. Docosahexaenoic acid (abbreviated DHA or 22:6n-3) is the major polyunsaturated acyl chain in these tissues. This study is directed towards determining a molecular basis for the modulation of G protein-coupled receptor signaling by polyunsaturated phospholipids, in particular those containing 22:6n-3 acyl chains. Studies are also focused on the response of these phospholipids to the acute exposure to ethanol. Fluorescence Energy Transfer (FRET) studies have demonstrated lateral domain formation in bilayers containing di16:0PC and di22:6 PC plus cholesterol, which was dependent on the presence of both cholesterol and rhodopsin. Continued FRET studies, along with atomic force microscopy and differential scanning calorimetry, are being pursued in order to characterize lateral domain formation in bilayers of 22:6n-3 containing lipids. Both acyl chain free volume and curvature stress have been invoked as bilayer properties, which modulate membrane protein function. Experiments indicate an inverse relationship between these two properties, suggesting that they may have opposite effects with respect to modulating protein function. Recent studies suggest that the dominant property in modulating membrane protein function will depend on the membrane lipid composition. Cholesterol-sphingomyelin interactions are thought to be the driving force for domain or raft formation in biological membranes. Our studies of the di16:0PC-di22:6PC-cholesterol-rhdopsin system demonstrate that a more general driving force for lateral domain formation is cholesterol-lipid interaction and that protein-lipid interaction can also be a contributing factor. In order to clarify the role of phospholipid composition in domain formation, the partitioning of cholesterol into bilayers of defined lipid composition was studied. A novel method of measuring cholesterol partitioning into lipid bilayers was developed. These studies show that cholesterol partitioning is determined by both phospholipid head group and acyl chain composition. Polyunsaturated acyl chains are among the most effective in reducing the level of cholesterol in lipid membranes, while trans fatty acids increase membrane cholesterol content. These studies are important in developing and understanding the role lipid composition in general and 22:6n-3 acyl chains in particular, in domain formation, the modulation of membrane protein function, the heterogeneous distribution of cholesterol in cell membranes, and the health benefits and deficits associated with polyunsaturated fatty acids and trans fatty acids, respectively.