Cyclodextrin-mediated removal of sterols from monolayers: Effects of sterol structure and phospholipids on desorption rate
Cyclodextrin-mediated removal of sterols from monolayers: Effects of sterol structure and phospholipids on desorption rate
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DOI：
10.1021/bi9528816
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发表时间：
1996-06-18
期刊：
影响因子：
2.9
通讯作者：
Slotte, JP
中科院分区：
文献类型：
--
作者：
Ohvo, H;Slotte, JP
在这项研究中，我们考察了一些影响从模型膜表面(在空气/水界面的单层)到环糊精(CD)在水相亚相中的脱附速率的参数。解吸实验是在恒定的表面压力和零级槽中进行的，这使得可以确定不受单层底物浓度影响的解吸速率。在20mN/m(30摄氏度)的表面压力下，0.9 mM的β-CD每分钟解吸约13pmoL的胆固醇，单层面积为平方厘米。胆固醇的解吸与时间呈线性关系，并且对亚相中的β-CD浓度很敏感。胆固醇的脱附速率随着单层表面压力的增加而增加(3-->35mN/m)，但随着温度的升高(15->30℃)略有下降。甾醇的解吸速率似乎受甾醇的相对极性影响。氧化的甾醇的脱附速度明显快于胆固醇(例如，4-胆固酮-3-酮的脱附速度是胆固醇的8.4倍)，而较低极性的甾醇的脱附速度较慢[例如，20(R)-异庚基-5-孕烯-3-β-醇，一种具有10个碳支链的胆固醇类似物，以胆固醇的1/10的速度脱附]。从同时含有胆固醇和磷脂的单层膜上解吸胆固醇比从纯胆固醇单层膜上解吸要慢得多。当比较二棕榈酰磷脂酰胆碱和N-棕榈酰鞘磷脂对胆固醇解吸率的影响时，发现鞘磷脂单层的胆固醇解吸比磷脂酰胆碱单分子层要慢得多。综上所述，这项研究的结果表明，β-CD增强的胆固醇(和其他甾醇)从单层膜上的解吸受到解吸分子的极性以及膜中脂/脂相互作用的影响。由于β-CD本身没有表面活性，因此它似乎是一种有用的、非侵入性的胆固醇解吸催化剂，有望成为膜和细胞研究中有价值的探针。
In this study, we have examined a number of parameters which affect the rate of sterol desorption from a model membrane surface (a monolayer at the air/water interface) to cyclodextrins (CD) in the aqueous subphase. The desorption experiments were carried out at a constant lateral surface pressure with a zero-order trough, which allowed for a determination of desorption rates which were unaffected by monolayer substrate concentration. At a surface pressure of 20 mN/m (30 degrees C), 0.9 mM beta-CD caused a desorption of about 13 pmol of cholesterol per minute and square centimeter of monolayer area. The desorption of cholesterol proceeded linearly as a time function and was sensitive to the concentration of beta-CD in the subphase. The rate of cholesterol desorption increased as the monolayer surface pressure increased (3 --> 35 mN/m) but decreased slightly with increasing temperature (15 --> 30 degrees C). The rate of sterol desorption appeared to be influenced by the relative polarity of the sterols. Oxidized sterols desorbed significantly faster than cholesterol (e.g., 4-cholesten-3-one desorbed 8.4-fold faster than cholesterol), whereas less polar sterols desorbed at slower rates [e.g., 20(R)-isoheptyl-5-pregnen-3 beta-ol, a cholesterol analogue with a ten-carbon branched side chain, desorbed at 1/10 of the rate of cholesterol]. Cholesterol desorption from a monolayer membrane containing both cholesterol and a phospholipid was much slower than from a pure cholesterol monolayer. When the effect of dipalmitoylphosphatidylcholine and N-palmitoylsphingomyelin on cholesterol desorption rate was compared, it was found that cholesterol desorption was much more retarded from sphingomyelin monolayers as compared to that from phosphatidylcholine monolayers. Taken together, the results of this study show that the beta-CD-enhanced desorption of cholesterol (and other sterols) from monolayer membranes is influenced by the polarity of the desorbing molecules, as well as by lipid/lipid interactions in the membranes. Since beta-CD has no surface activity of its own, it appears to be a useful, nonintrusive catalyzer of cholesterol desorption and is expected to become a valuable probe in membrane and cell research.