Sklar L A, Hudson B S, Simoni R D
Biochemistry. 1977 Mar 8;16(5):819-28. doi: 10.1021/bi00624a002.
The preparation of polyene fatty acid membrane probes cis- and trans-parinaric acid and parinaroylphosphatidylcholines and their use in studies of several one- and two- component lipid systems are described. The fluorescence quantum yield of trans-parinaric acid in dipalmitoylphosphatidylcholine at 20 degrees C is approximately 0.3; the quantum yield in aqueous solution is negligibly small. Thermal-phase transitions in single-component phospholipid dispersions are monitored with absorption and fluorescence excitation peak position, fluorescence intensity, lifetime, and polarization. The transition temperatures observed are consistent with previous determinations. Shifts in the absorption peak position are related to the bilayer expansion as it undergoes the gel to liquid-crystalline transition, while fluorescence depolarization provides semiquantitative information concerning molecular motion of the probe in the bilayer. A long fluorescence lifetime component is observed for parinaric acid in the solid phase (up to 50 ns), and a short lifetime component is observed (ca. 5 ns) in the fluid phase of dipalmitoylphosphatidylcholine; both lifetime components are observed in the transition region. In most phospholipids, cis-parinaric acid detects the melting transition at about 1 degree C lower than trans-parinaric acid. Partitioning experiments involving mixed populations of phospholipid vesicles show that trans-parinaric acid preferentially associates with solid-phase lipids, while cis-parinaric acid shows a more equal distribution between solid and fluid lipids. The binding of cis-parinaric acid to dipalmitoylphosphatidylcholine at 25 degrees C is described as partitioning of parinaric acid between lipid vesicles and the aqueous phase with a partition coefficient of 5 X 10(5). Several rates are observed in the binding process which are interpreted as rapid outer monolayer uptake and a much slower process of interlamellar exchange. The phase diagram of the binary lipid mixture dipalmitoylphosphatidylcholine-dipalmitoylphosphatidylethanolamine has also been examined and found to be essentially identical to the one constructed using a nitroxide probe.
描述了多烯脂肪酸膜探针顺式和反式十八碳四烯酸以及十八碳四烯酰磷脂酰胆碱的制备及其在几种单组分和双组分脂质体系研究中的应用。20℃时，反式十八碳四烯酸在二棕榈酰磷脂酰胆碱中的荧光量子产率约为0.3；在水溶液中的量子产率可忽略不计。通过吸收和荧光激发峰位置、荧光强度、寿命和偏振来监测单组分磷脂分散体中的热相变。观察到的转变温度与先前的测定结果一致。吸收峰位置的变化与双层从凝胶态到液晶态转变时的膨胀有关，而荧光去极化提供了有关探针在双层中分子运动的半定量信息。在固相（高达50 ns）中观察到十八碳四烯酸有一个长荧光寿命组分，在二棕榈酰磷脂酰胆碱的流体相中观察到一个短寿命组分（约5 ns）；在转变区域都观察到了这两个寿命组分。在大多数磷脂中，顺式十八碳四烯酸检测到的熔化转变温度比反式十八碳四烯酸低约1℃。涉及磷脂囊泡混合群体的分配实验表明，反式十八碳四烯酸优先与固相脂质结合，而顺式十八碳四烯酸在固相和流体脂质之间的分布更为均匀。25℃时顺式十八碳四烯酸与二棕榈酰磷脂酰胆碱的结合被描述为十八碳四烯酸在脂质囊泡和水相之间的分配，分配系数为5×10⁵。在结合过程中观察到几种速率，可解释为快速的外层单分子层摄取和一个慢得多的层间交换过程。还研究了二元脂质混合物二棕榈酰磷脂酰胆碱 - 二棕榈酰磷脂酰乙醇胺的相图，发现其与使用氮氧化物探针构建的相图基本相同。
