FLUORESCENCE STUDIES OF BIOPHYSICAL PROPERTIES OF POLYUN

神经元和视网膜组织富含磷脂， 一个或两个多不饱和酰基链。 我们的研究导致了 开发了一种新的磷脂酰基链堆积模型， 涉及在表面中动态横向域的形成， 膜的 通过差示扫描量热法（DSC）对以下物质的混合物进行分析： 二饱和（二16：0）磷脂酰胆碱（PC）和二多不饱和磷脂酰胆碱（PC）， (di22：6n3）PC进行了研究。 这些脂质在细胞中显示出差的可溶解性。 液晶（LC）相，并证明横向相分离 在凝胶阶段。 荧光寿命和各向异性测量， 使用探针二苯基己三烯（DPH），也表明存在 凝胶和液体中膜表面的横向不均匀性 晶体状态 这些研究支持集群的存在， 混合链和二聚不饱和磷脂的混合物中的结构域， 存在于突触体和视网膜膜中。 的倾向 形成结构域随着酰基链不饱和度水平的增加而增加， 其中22：6N3酰基显示出最高水平的结构域形成。 两 DSC和荧光数据表明，胆固醇优先 与饱和酰基链相互作用，因此， 集中在膜的更饱和的区域， 影响域的大小和寿命。 这些发现 对整合膜蛋白的潜在重要意义 功能 结构域的形成会在膜上产生富含 高度不饱和的酰基链。位于这些区域的蛋白质 具有与更饱和区域不同的功能特性 的膜。 许多神经递质受体和视色素 G蛋白偶联受体家族的成员，并存在于膜中 含有非常高水平的多不饱和酰基链， 所描述的类型可能会发生。 DSC测量表明 多不饱和磷脂对干扰更敏感 乙醇的性质。 因此，形成高度不饱和的 结构域可能导致突触体膜的区域， 对醇和其它膜可溶性试剂特别敏感。 荧光探针已被广泛用于表征酰基链 模型和生物模型中脂质双层的堆积性质 膜。 我们扩展了时间分辨各向异性的分析 最常用的探针之一DPH的衰减，以允许测量 膜内部酰基链堆积顺序与 更接近界面区域。 这些数据补充了 信息和表征的时间平均性能的NMR 构成双层的分子集合。 这一分析使更多的 磷脂酰基堆积性质的精细判别 链及其与胆固醇的相互作用。

Neuronal and retinal tissue are high in phospholipids containing either one or two polyunsaturated acyl chains. Our studies have led to the development of a novel model for phospholipid acyl chain packing, which involves the formation of dynamic lateral domains in the surface of the membrane. Differential scanning calorimetry (DSC) of mixtures of a disaturated (di16:0) phospha-tidylcholine (PC) and a dipolyunsaturated (di22:6n3) PC were studied. These lipids show poor miscibility in the liquid crystalline (LC) phase and demonstrate lateral phase separation in the gel phase. Fluorescence lifetime and anisotropy measurements, using the probe diphenylhexatriene (DPH), also indicates the presence of lateral heterogeneity in the membrane surface in both the gel and liquid crystal states. These studies support the presence of clusters or domains in mixtures of mixed chain and dipolyunsaturated phospholipids, as exist in both synaptosomal and retinal membranes. The propensity to form domains increases with increasing levels of acyl chain unsaturation, with 22:6n3 acyl showing the greatest level of domain formation. Both DSC and fluorescence data demonstrate that cholesterol preferentially interacts with saturated acyl chains and would, therefore, tend to concentrate in the more saturated regions of the membrane where it would effect both the size and lifetime of the domains. These findings have potentially important implications for integral membrane protein function. Domain formation would create regions of the membrane rich in highly unsaturated acyl chains. Proteins located in these regions would have different functional properties than those in more saturated regions of the membrane. Many neurotransmitter receptors and visual pigments are members of the G protein coupled-receptor family and reside in membranes containing very high levels of polyunsaturated acyl chains where domains of the type described are likely to occur. DSC measurements indicate that polyunsaturated phospholipids are more sensitive to the perturbing nature of ethanol. Therefore, the formation of highly unsaturated domains could result in regions of the synaptosomal membranes which are particularly sensitive to alcohols and other membrane soluble agents. Fluorescent probes have been widely used to characterize the acyl chain packing properties of lipid bilayers in both model and biological membranes. We have extended the analysis of the time-resolved anisotropy decay of one of the most commonly used probes, DPH, to allow a measure of the acyl chain packing order in the membrane interior vs the portion of the chain closer to the interfacial region. These data complement the information from NMR and characterize the time averaged properties of the ensemble of molecules making up the bilayer. This analysis allows a more refined discrimination of the packing properties of phospholipid acyl chains and their interaction with cholesterol.