FLUORESCENCE STUDIES OF BIOPHYSICAL PROPERTIES OF POLYUNSATURATED PHOSPHOLIPIDS

神经元和视网膜组织中的磷脂含量很高。 含有一个或两个多不饱和酰基链的。按顺序 为了更好地表征酰基链的堆积性能 多不饱和磷脂，我们开发了一种精制的 自由滚流的时间分辨各向异性衰减分析 膜探头。在这些研究中，我们使用了疏水性 荧光探针二苯基己三烯(DPH) 常用的探头。这种分析允许测量酰基 膜内部的链式包装顺序与 更接近界面区域的链条，并提供补充 与从分子内有序参数获得的信息相同 源自核磁共振。与核磁共振数据形成对比，核磁共振数据反映了 单个分子的性质，荧光数据是 表示集合的时间平均性质 组成双层的脂类分子。这些研究表明 多不饱和酰基链的存在导致了 最高程度的酰链无序，并产生最高的值 酰链堆积自由体积。后一个参数已被 表现出最大程度的促进活性的形成 G蛋白偶联受体视紫红质的构象。 胆固醇已被证明减少了两种酰基链的堆积 游离量和视紫红质激活。我们的研究表明 多不饱和磷脂能够抵抗有序化效应 并保持其独特的酰基链堆积 属性。这些发现对积分具有重要的意义 膜蛋白的功能和提示高度不饱和 在视网膜和神经元组织中发现的磷脂可以优化 受体的功能，并能够抵抗某些 成分变化，如胆固醇含量的增加。

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.