FLUORESCENCE STUDIES OF BIOPHYSICAL PROPERTIES OF POLYUNSATURATED PHOSPHOLIPIDS

神经元和视网膜组织的磷脂含量很高 含有一个或两个多不饱和酰基链。为了 为了更好地表征 多不饱和磷脂，我们开发了一种精制的 自由翻滚的时间分辨各向异性衰减分析 膜探针在这些研究中，我们使用了疏水的 荧光探针二苯基己三烯（DPH）， 常用的探针。该分析允许测量酰基 在膜内部的链包装顺序与部分的 链更接近界面区域，并提供互补的 从分子内有序参数获得信息 源自NMR。与NMR数据相反，NMR数据反映了 单个分子的性质，荧光数据是 的集合的时间平均属性的代表 构成双层的脂质分子。这些研究证明 多不饱和酰基链的存在导致 最高程度的酰基链无序，并产生最高的值 的酰基链堆积自由体积。后一个参数已被 显示出促进最大程度的活化 G蛋白偶联受体视紫红质的构象。 胆固醇已被证明可以减少酰基链堆积 自由体积和视紫红质活化。我们的研究表明， 多不饱和磷脂能够抵抗有序效应 并保持其独特的酰基链包装 特性.这些发现对积分具有重要意义。 膜蛋白的功能，并建议高度不饱和 在视网膜和神经组织中发现的磷脂可以优化 受体功能，并能够抵抗某些 成分变化，如胆固醇含量增加。

Neuronal and retinal tissue are high in phospholipids containing either one or two polyunsaturated acyl chains. In order to better characterize the acyl chain packing properties of polyunsaturated phospholipids, we have developed a refined analysis of the time resolved anisotropy decay of free tumbling membrane probes. In these studies we have used the hydrophobic fluorescence probe diphenylhexatriene (DPH), one of the most commonly used probes. This analysis allows a measure of the acyl chain packing order in the membrane interior vs the portion of the chain closer to the interfacial region and provides complementary information to that obtained from intramolecular order parameters derived from NMR. In contrast to NMR data, which reflects the properties of individual molecules, the fluorescence data is representative of the time averaged properties of the ensemble of lipid molecules composing the bilayer. These studies demonstrate that the presence of polyunsaturated acyl chains results in the highest degree of acyl chain disorder and produce the highest values of acyl chain packing free volume. This latter parameter has been shown to promote the greatest degree of formation of the activate conformation of the G protein-coupled receptor, rhodopsin. Cholesterol has been shown to decrease both acyl chain packing free volume and rhodopsin activation. Our studies show that polyunsaturated phospholipids are able to resist the ordering effects of cholesterol and maintain their unique acyl chain packing properties. These findings have important implications for integral membrane protein function and suggest that highly unsaturated phospholipids found in retina and neuronal tissue can optimize receptor function and are able to resist the effects of certain compositional variation, such as increases in cholesterol content.