Phase behavior and aggregate formation for the aqueous monoolein system mixed with sodium oleate and oleic acid
Phase behavior and aggregate formation for the aqueous monoolein system mixed with sodium oleate and oleic acid
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DOI：
10.1021/la010650w
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发表时间：
2001-12-11
期刊：
影响因子：
3.9
通讯作者：
Khan, A
中科院分区：
文献类型：
--
作者：
Borné, J;Nylander, T;Khan, A
采用光学显微镜、低温透射电镜、小角x射线衍射和核磁共振等方法，研究了单油酸(MO)-油酸钠（NaO)-水(H2O)- h -2）和MO-油酸(OA)-(H2O)- h -2三元体系的相行为和微观结构。结果表明，两种体系的相行为存在显著差异。MO-NaO-(H2O)- h -2体系的等温相图以大片层状液晶相为主，在高含水量时表现出理想的膨胀。稳定的囊泡是主要的团聚体在水浓度bbb90 wt%。然而，MO-OA-(H2O)- h -2体系中不存在片层相，在低含水量下，最大的单相区是反六方液晶相HII。在MO-NaO-(H2O)- h -2体系中也发现了类似的缺水Hii相。由二元MO-(H2O)- h -2体系形成的两种双连续立方结构——陀螺（C-G）和菱形（C-D）也存在于三元体系中。发现由NaO三元体系最初形成的单个C-G相的一部分是亚稳的，并在几周内变得不稳定，剩下的C-G相与系统的其他热力学稳定相一样稳定。油酸体系具有反胶束型结构的立方相。实验确定的相图和相结构可以定性地理解结合静电效应的脂质分子的几何形状。
The phase behavior and microstructure of the two ternary systems monoolein (MO)-sodium oleate (NaO)-water ((H2O)-H-2) and MO-oleic acid (OA)-(H2O)-H-2 are studied by a combination of optical microscopy, cryo-transmission electron microscopy, small-angle X-ray diffraction, and NMR methods. The results demonstrate significant differences in phase behavior between the two systems. The isothermal phase diagram of the MO-NaO-(H2O)-H-2 system is dominated by a large lamellar liquid crystalline phase that shows an ideal swelling up to high water contents. Stable vesicles are the dominant aggregates at water concentration > 90 wt%. The existence of a lamellar phase is, however, absent from the MO-OA-(H2O)-H-2 system, where the largest single-phase region is a reversed hexagonal liquid crystalline phase, HII, at low water content. A similar water-poor Hii phase is also identified for the MO-NaO-(H2O)-H-2 system. The two types of bicontinuous cubic structures, gyroid (C-G) and diamond (C-D), formed by the binary MO-(H2O)-H-2 system are also present in the ternary systems. Part of the single C-G phase initially formed by the ternary system with NaO is found to be metastable and becomes destabilized within a few weeks, leaving the rest of the C-G phase which is stable like other thermodynamically stable phases for the system. A cubic phase with a reversed micellar type structure is characterized for the oleic acid system. The experimentally determined phase diagrams and the phase structures can be qualitatively understood in terms of the geometry of the lipid molecule in combination with electrostatic effects.