EFFECTS OF POLAR CAROTENOIDS ON DIMYRISTOYLPHOSPHATIDYLCHOLINE MEMBRANES - A SPIN-LABEL STUDY
EFFECTS OF POLAR CAROTENOIDS ON DIMYRISTOYLPHOSPHATIDYLCHOLINE MEMBRANES - A SPIN-LABEL STUDY
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DOI：
10.1016/0005-2736(92)90167-k
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发表时间：
1992-03-23
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影响因子：
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通讯作者：
SIELEWIESIUK, J
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文献类型：
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作者：
SUBCZYNSKI, WK;MARKOWSKA, E;SIELEWIESIUK, J
用自旋标记方法研究了二肉豆蔻基磷脂酰胆碱(DMPC)膜的结构和动态性质随温度和极性类胡萝卜素摩尔分数的变化。结果表明：(1)硬脂酸自旋标记显示，类二羟基胡萝卜素、玉米黄质和紫黄质增加了脂类脂烷基链的有序性，降低了运动自由度，降低了柔韧性梯度。当玉米黄质的摩尔分数为10%时，16-十二烷基硬脂酸自旋标记的旋转扩散活化能降低约35%。(2)类胡萝卜素增加了DMPC的极性头基团的迁移率，并增加了膜上该区域的水可及性，如坦泊胆碱磷脂酸酯所显示的那样。(3)如胆烷自旋标记(CSL)和雄烷自旋标记(ASL)所示，在类胡萝卜素存在下，溶解在DMPC膜中的刚性和高各向异性分子表现出更大的运动级数。类胡萝卜素降低CSL的重定向运动速率，但不影响ASL的速率，这可能是由于缺少异辛基侧链所致。在DMPC双层膜的主相变处观察到的自旋标记物运动的突变在类胡萝卜素的存在下变宽并消失。在凝胶相膜中，极性类胡萝卜素增加了大多数自旋标记物的运动自由度，显示了类胡萝卜素对膜流动性的调节作用。我们的结果支持Rohmer，M.，Bouvier，P.和Ourisson，G.(1979)Proc的假说。娜塔莉。阿卡德。SCI。美国76,847-851，类胡萝卜素调节原核生物的膜流动性，就像胆固醇调节真核生物的膜流动性一样。提出了一个模型来解释这些结果，即刚性棒状极性类胡萝卜素分子插入膜增加了烷基链的扩展反式构象，减少了双层中心的自由空间，分离了磷脂酰胆碱头基，减少了它们之间的相互作用。
Spin labeling methods were used to study the structure and dynamic properties of dimyristoylphosphatidylcholine (DMPC) membranes as a function of temperature and the mole fraction of polar carotenoids. The results in fluid phase membranes are as follows: (1) Dihydroxycarotenoids, zeaxanthin and violaxanthin, increase order, decrease motional freedom and decrease the flexibility gradient of alkyl chains of lipids, as was shown with stearic acid spin labels. The activation energy of rotational diffusion of the 16-doxylstearic acid spin label is about 35% less in the presence of 10 mol% of zeaxanthin. (2) Carotenoids increase the mobility of the polar headgroups of DMPC and increase water accessibility in that region of membrane, as was shown with tempocholine phosphatidic acid ester. (3) Rigid and highly anisotropic molecules dissolved in the DMPC membrane exhibit a bigger order of motion in the presence of polar carotenoids as was shown with cholestane spin label (CSL) and androstane spin label (ASL). Carotenoids decrease the rate of reorientational motion of CSL and do not influence the rate of ASL, probably due to the lack of the isooctyl side chain. The abrupt changes of spin label motion observed at the main phase transition of the DMPC bilayer are broadened and disappear at the presence of 10 mol% of carotenoids. In gel phase membranes, polar carotenoids increase motional freedom of most of the spin labels employed showing a regulatory effect of carotenoids on membrane fluidity. Our results support the hypothesis of Rohmer, M., Bouvier, P. and Ourisson, G. (1979) Proc. Natl. Acad. Sci. USA 76, 847-851, that carotenoids regulate the membrane fluidity in Procaryota as cholesterol does in Eucaryota. A model is proposed to explain these results in which intercalation of the rigid rod-like polar carotenoid molecules into the membrane enhances extended trans-conformation of the alkyl chains, decreases free space in the bilayer center, separate the phosphatidylcholine headgroups and decreases interaction between them.