Matrix effect in the size distribution of fatty acid vesicles
Matrix effect in the size distribution of fatty acid vesicles
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DOI：
10.1021/jp981234w
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发表时间：
1998-12-10
影响因子：
3.3
通讯作者：
Luisi, PL
中科院分区：
文献类型：
--
作者：
Blöchliger, E;Blocher, M;Luisi, PL
研究了不同条件下油酸/油酸微囊形成的协同作用机理。当油酸钠的原始溶液被注入到pH为8.8的缓冲水溶液中时，囊泡形成的时间进程遵循S形模式，这表明这是一个自催化过程。根据浊度和电子显微镜的测量，在存在预先添加的囊泡的情况下，运行实验证明了自催化作用，它缩短了滞后期并加速了囊泡的形成过程。通过在缓冲溶液中注入表面活性剂原料溶液而获得的囊泡直径的尺寸分布覆盖很宽的范围，通常在50 nm和1.5微米之间。然而，当存在直径分别为50 nm和100 nm的挤压囊泡时，观察到完全不同的情况：然后，尺寸分布更窄，并且强烈偏向预先添加的囊泡的直径(即，50或100 nm)。这就好像原来存在的小泡会对新的小泡施加一种模板(或基质)效应。在不同浓度条件下，研究了预加囊泡和添加表面活性剂原液的这种“基质”效应。在非均相体系中，不溶于水和包覆的油酸酐在有无预加小泡的情况下被水解，并且有倾向地观察到相同的基质效应。有人认为，这很可能是由于注入的表面活性剂与已经存在的小泡的先决条件结合，而正是这种结合决定了最终的尺寸分布。
The cooperative mechanism of oleic acid/oleate vesicle formation is investigated under a variety of conditions. When a stock solution of sodium oleate is injected in a buffered aqueous solution of pH 8.8, the time progress of the vesicles formation follows a sigmoidal pattern, which is indicative of an autocatalytic process. Autocatalysis is demonstrated by running experiments in the presence of preadded vesicles, which shortens the lag phase and accelerates the process of vesicle formation as measured by turbidity and electron microscopy. The size distribution of the vesicle diameters obtained by injection of the surfactant stock solution in buffer solution covers a wide range, typically between 50 nm and 1.5 mu m. However, in the presence of extruded vesicles having respectively 50 and 100 nm diameter, a quite different situation is observed: the size distribution is then much narrower and strongly biased toward the diameter of the preadded vesicles (i.e., 50 or 100 nm). It is as if the vesicles which are originally present would exercise a kind of template (or matrix) effect upon the new vesicles. This "matrix" effect is studied under a variety of concentration conditions of the preadded vesicles and the added surfactant stock solution. It is also investigated with a heterogeneous system, in which the water-insoluble and overlaid oleic anhydride is hydrolyzed in the presence and in the absence of preadded vesicles, and tendentiously the same matrix effect is observed. It is argued that this is most likely due to a prerequisite binding of the injected surfactant to the already existing vesicles, and it is this binding which determines the final size distribution.