Roux Michel, Moutard Stéphane, Perly Bruno, Djedaini-Pilard Florence
Commissariat à l'Energie Atomique/Direction des Sciences du Vivant/Institut de Biologie et Technologies de Saclay, URA CNRS, Service de Bioénergétique, Biologie Structurale et Mécanismes, Gif sur Yvette Cedex, France.
Biophys J. 2007 Sep 1;93(5):1620-9. doi: 10.1529/biophysj.106.099945. Epub 2007 May 11.
Cyclodextrins are hydrophilic molecular cages with a hydrophobic interior allowing the inclusion of water-insoluble drugs. Amphiphilic cyclodextrins obtained by appending a hydrophobic anchor were designed to improve the cell targeting of the drug-containing cavities through their liposome transportation in the organism. After insertion in model membranes, they were found to induce a lateral phase separation into a pure lipid phase and a fluid cyclodextrin-rich phase (L(CD)) with reduced acyl chain order parameters, as observed with a derivative containing a cholesterol anchor (M. Roux, R. Auzely-Velty, F. Djedaïni-Pilard, and B. Perly. 2002. Biophysical Journal, 8:813-822). We present another class of amphiphilic cyclodextrins obtained by grafting aspartic acid esterified by two lauryl chains on the oligosaccharide core via a succinyl spacer. The obtained dilauryl-beta-cyclodextrin (betaDLC) was inserted in chain perdeuterated dimyristoylphosphatidylcholine (DMPC-d54) membranes and studied by deuterium NMR ((2)H-NMR). A laterally segregated mixed phase was found to sequester three times more lipids than the cholesteryl derivative (approximately 4-5 lipids per monomer of betaDLC), and a quasipure L(CD) phase could be obtained with a 20% molar concentration of betaDLC. When cooled below the main fluid-to-gel transition of DMPC-d54 the betaDLC-rich phase stays fluid, coexisting with pure lipid in the gel state, and exhibits a sharp transition to a gel phase with frozen DMPC acyl chains at 12.5 degrees C. No lateral phase separation was observed with partially or fully methylated betaDLC, confirming that the stability of the segregated L(CD) phase was governed through hydrogen-bond-mediated intermolecular interactions between cyclodextrin headgroups at the membrane surface. As opposed to native betaDLC, the methylated derivatives were found to strongly increase the orientational order of DMPC acyl chains as the temperature reaches the membrane fluid-to-gel transition. The results are discussed in relation to the "anomalous swelling" of saturated phosphatidylcholine multilamellar membranes known to occur in the vicinity of the main fluid-to-gel transition.
环糊精是具有疏水内部的亲水性分子笼，能够包合水不溶性药物。通过连接疏水锚定基团得到的两亲性环糊精，旨在通过其在生物体内的脂质体运输来改善含药腔的细胞靶向性。插入模型膜后，发现它们会诱导横向相分离，形成纯脂质相和富含环糊精的流体相（L(CD)），其酰基链序参数降低，这与含有胆固醇锚定基团的衍生物的情况一致（M. Roux、R. Auzely-Velty、F. Djedaïni-Pilard和B. Perly。2002年。《生物物理杂志》，8:813 - 822）。我们展示了另一类两亲性环糊精，它是通过在寡糖核心上经由琥珀酰间隔基接枝由两条月桂酰链酯化的天冬氨酸而获得的。所得到的二月桂酰-β-环糊精（βDLC）被插入到全氘代二肉豆蔻酰磷脂酰胆碱（DMPC-d54）膜中，并通过氘核磁共振（(2)H-NMR）进行研究。发现横向分离的混合相隔离的脂质比胆固醇衍生物多三倍（每βDLC单体约4 - 5个脂质），并且在βDLC摩尔浓度为20%时可获得准纯的L(CD)相。当冷却至低于DMPC-d54的主要流体-凝胶转变温度时，富含βDLC的相保持流体状态，与处于凝胶态的纯脂质共存，并在12.5℃时表现出向具有冻结DMPC酰基链的凝胶相的急剧转变。部分或完全甲基化的βDLC未观察到横向相分离，这证实了隔离的L(CD)相的稳定性是通过膜表面环糊精头基之间氢键介导的分子间相互作用来控制的。与天然βDLC相反，发现甲基化衍生物在温度达到膜的流体-凝胶转变时会强烈增加DMPC酰基链的取向有序度。结果结合已知在主要流体-凝胶转变附近发生的饱和磷脂酰胆碱多层膜的“异常膨胀 ”进行了讨论。
