FLUORESCENCE STUDIES OF BIOPHYSICAL PROPERTIES OF POLYUN

神经细胞和视网膜组织富含含有一个或两个长链多不饱和酰基链的磷脂。我们对疏水荧光探针二苯基己三烯(DPH)的时间分辨各向异性衰减的分析进一步完善，允许测量膜内部的酰基链堆积顺序与靠近界面区域的链部分。多不饱和酰链导致最高程度的酰链无序，并产生最高值的酰链堆积自由体积，这一参数促进了G蛋白偶联受体视紫红质活性构象的最大形成。胆固醇已被证明降低了酰链堆积自由体积和视紫红质的激活。我们的研究表明，多不饱和磷脂能够抵抗胆固醇的有序性，并保持其独特的酰基链堆积性质。最近的研究结果表明，由于磷脂头基团的脱水，随着渗透压力的增加，酰基链堆积增加。另一方面，乙醇具有降低酰基链有序度的拮抗作用。这些效应对于理解酒精作用的体内机制很重要，因为乙醇效应发生在血浆的渗透背景下。这些发现对膜蛋白的整体功能具有重要意义，并提示视网膜和神经元组织中的高度不饱和磷脂可以优化受体功能，能够抵抗某些成分变化的影响，如胆固醇含量的增加，并可能调节膜对乙醇的敏感性。-神经科学、营养失调

Neuronal and retinal tissue are high in phospholipids containingone or two long chain polyunsaturated acyl chains. A further refinement of our analysis of the time-resolved anisotropy decay of the hydrophobic fluorescence probe diphenylhexatriene (DPH) allows a measure of the acyl chain packing order in the membrane interior vs the portion of the chain closer to the interfacial region. Polyunsaturated acyl chains result in the highest degree of acyl chain disorder and produce the highest values of acyl chain packing free volume, a parameter which promotes 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. Recent findings demonstrate that acyl chain packing is increased by increased osmotic stress, due to the dehydration of the phospholipid head group. Ethanol on the other hand has an antagonistic effect of decreasing acyl chain order. These effects are important in understanding in vivo mechanisms of alcohol action since ethanol effects occur in the presence of an osmotic background of plasma. 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, are able to resist the effects of certain compositional variation, such as increases in cholesterol content, and may modulate membrane sensitivity to ethanol. - neurosciences, nutritional disorders