A Stimulus-Responsive Shape-Persistent Micelle Bearing a Calix[4]arene Building Block: Reversible pH-Dependent Transition between Spherical and Cylindrical Forms
A Stimulus-Responsive Shape-Persistent Micelle Bearing a Calix[4]arene Building Block: Reversible pH-Dependent Transition between Spherical and Cylindrical Forms
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DOI：
10.1021/la2037668
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发表时间：
2012-02-14
期刊：
影响因子：
3.9
通讯作者：
Mylonas, Efstratios
中科院分区：
文献类型：
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作者：
Fujii, Shota;Sanada, Yusuke;Mylonas, Efstratios
合成了一系列不同长度烷基链的阳离子杯[4]芳烃基脂质，其中丙基尾和己基尾的分别记为CaL[4]C3和C6，在低pH（胺头基质子化状态）下形成球形胶束.随着pH值的增加，去质子化后，CaL[4]C3显示出球形到圆柱体的转变，而CaL[4]C6则从球形变成圆柱体，再变成单层囊泡。球形和圆柱形CaL[4]C3胶束的同步加速器小角X射线散射（SAXS）图案表现出尖锐的强度最小值，表明形状单分散性。通过分析超离心（AUC）进一步证实了CaL[4]C3球形胶束的单分散性。SAXS、AUC和静态光散射一致地表明聚集数为6。相比之下，CaL[4]C6表现出多分散性，平均聚集数为12。当烷基链的碳数增加到9（CaL[4]C9）时，在低pH下形成圆柱体，而在高pH下，不能观察到清晰的形态。目前的结果表明，一个非常精确的组合的尾部长度，头部体积，和刚性的积木是需要产生形状持久性胶束和形状持久性可以保持在结构转变。用从头算形状确定程序对球形CaL[4]C3胶束进行了分子模型的重建。
A series of cationic calix[4]arene-based lipids with alkyl chains of varying length were newly synthesized, and the ones with propyl and hexyl tails, denoted by CaL[4]C3 and C6, respectively, were found to form spherical micelles at low pH (protonated state of the amine headgroup). Upon deprotonation with increasing pH, CaL[4]C3 showed a sphere-to-cylinder transition, while CaL[4]C6 changed from sphere, to cylinder, to monolayer vesicle. Synchrotron small-angle X-ray scattering (SAXS) patterns from both spherical and cylindrical CaL[4]C3 micelles exhibited a sharp intensity minimum, indicating shape monodispersity. The monodispersity of the CaL[4]C3 spherical micelles was further confirmed by analytical ultracentrifugation (AUC). SAXS, AUC, and static light scattering agreeingly indicated an aggregation number of 6. In contrast, CaL[4]C6 exhibited polydispersity with an average aggregation number of 12. When the number of carbons of the alkyl chain was increased to 9 (CaL[4]C9), cylinder formed at low pH, while at high pH, no clear morphology could be observed. The present results indicate that a very precise combination of tail length, head volume, and rigidity of the building block is required to produce shape-persistent micelles and that the shape-persistence can be maintained upon a structural transition. An attempt to reconstruct a molecular model for the spherical CaL[4]C3 micelle was made With an ab initio shape determining program.