SPIN-LABEL STUDIES ON PHOSPHATIDYLCHOLINE-CHOLESTEROL MEMBRANES - EFFECTS OF ALKYL CHAIN-LENGTH AND UNSATURATION IN THE FLUID PHASE
SPIN-LABEL STUDIES ON PHOSPHATIDYLCHOLINE-CHOLESTEROL MEMBRANES - EFFECTS OF ALKYL CHAIN-LENGTH AND UNSATURATION IN THE FLUID PHASE
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DOI：
10.1016/0005-2736(86)90124-0
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发表时间：
1986-01-29
期刊：
影响因子：
--
通讯作者：
MERKLE, H
中科院分区：
文献类型：
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作者：
KUSUMI, A;SUBCZYNSKI, WK;MERKLE, H
磷脂酰胆碱-胆固醇膜的流体相和水的可及性的膜的动力学特性已被研究作为磷脂烷基链的长度，饱和度，胆固醇的摩尔分数，和温度的函数，通过使用自旋和荧光标记方法。结果如下：（1）.胆固醇对饱和磷脂酰胆碱膜中5-羟基硬脂酸自旋标记（5-SASL）和16-羟基硬脂酸自旋标记（16-SASL）运动自由度的影响显著大于烷基链长度和在烷基链中引入不饱和度的影响。(2)饱和磷脂的烷基链长度的变化，不改变胆固醇的影响，除了在二月桂酰磷脂酰胆碱的情况下，它具有最短的烷基链（12个碳）在这项工作中使用。(3)烷基链的不饱和大大降低了胆固醇在C-5和C-16位的有序化效果，尽管不饱和单独仅产生较小的流化效果。(4)将30 mol%胆固醇引入二肉豆蔻酰磷脂酰胆碱膜可使脂质的侧向扩散常数降低4倍，而在二油酰磷脂酰胆碱膜中仅引起侧向扩散的轻微降低。(5)如果在相同温度下比较，作为二肉豆蔻酰磷脂酰胆碱-、二棕榈酰磷脂酰胆碱-和二硬脂酰磷脂酰胆碱-胆固醇膜的流体相中胆固醇摩尔分数的函数绘制的5-SASL迁移率在宽的温度范围（45 - 82 ℃）内是相似的。C）和胆固醇摩尔分数（0.50%）。(6)在饱和磷脂酰胆碱膜的等温实验中。5-SASL最大限度地固定在区域I和III之间的相边界处，由其他工作者报道（Recktenald，D. J.和McConnell，H.M.（1981）Biochemistry 20，4505-4510），并且在区域I和III中远离边界变得更加移动的。(7)5-SASL在不饱和磷脂酰胆碱膜中的固定随胆固醇摩尔分数的增加而逐渐单调，在所研究的胆固醇摩尔分数范围内没有显示出任何最大值。(8)通过严格确定刚性极限磁参数的胆甾烷自旋标记膜从Q-带二阶导数ESR谱监测周围的氮氧自由基的介电环境，它的结论是，胆固醇掺入增加水的可及性在亲水位点的膜。与此相反，12-（9-anthrooxy）硬脂酸荧光显示，水的可及性降低的疏水位点的膜。
Dynamic properties of phosphatidylcholine-cholesterol membranes in the fluid phase and water accessibility to the membranes have been studied as a function of phospholipid alkyl chain length, saturation, mole fraction of cholesterol, and temperature by using spin and fluorescence labeling methods. The results are the following: (1). The effect of cholesterol on motional freedom of 5-doxyl stearic acid spin label (5-SASL) and 16-doxyl stearic acid spin label (16-SASL) in saturated phosphatidylcholine membrane is significantly larger than the effects of alkyl chain length and introduction of unsaturation in the alkyl chain. (2) Variation of alkyl chain length of saturated phospholipids, does not alter the effects of cholesterol except in the case of dilauroylphosphatidylcholine, which possess the shortest alkyl chains (12 carbons) used in this work. (3) Unsaturated of the alkyl chains greatly reducs the ordering effect of cholesterol at C-5 and C-16 positions although unsaturation alone gives only minor fluidizing effects. (4) Introduction of 30 mol% cholesterol to dimyristoylphosphatidylhcoline membranes decreases the lateral diffusion constants of lipids by a factor of four while it causes only a slight decrease of lateral diffusion in dioleoylphosphatidylcholine membranes. (5) If compared at the same temperature, 5-SASL mobilities plotted as a function of mole fraction of cholesterol in the fluid phases of dimyristoylphosphatidylcholine-, dipalmitoylphosphatidylcholine- and distearoylphosphatidylcholine-cholesterol membranes are similar in wide ranges of temperature (45-82.degree. C) and cholesterol mole fraction (0.50%). (6) In isothermal experiments with saturated phosphatidylcholine membranes. 5-SASL is maximally immobilized at the phase boundary between Regions I and III reported by other workers (Recktenald, D.J. and McConnell, H.M. (1981) Biochemistry 20, 4505-4510) and becomes more mobile away from the boundary in Regions I and III. (7) 5-SASL in unsaturated phosphatidylcholine membranes showed a gradual monotonic immobilization with increase of cholesterol mole fraction without showing any maximum in the range of cholesterolfractions studied. (8) By rigorously determining rigid-limit magnetic parameters of cholestane spin labels in membranes from Q-band second-derivative ESR spectra to monitor the dielectric environment around the nitroxide radical, it is concluded that cholesterol incorporation increases water accessibility in the hydrophilic loci of the membrane. In contrast, 12-(9-anthroyloxy)stearic acid fluorescence showed that water accessibility is decreased in the hydrophobic loci of the membrane.