Vargas R, Mariani P, Gulik A, Luzzati V
Laboratoire Propre du CNRS Associé à l'Université Pierre et Marie Curie, Yvette, France.
J Mol Biol. 1992 May 5;225(1):137-45. doi: 10.1016/0022-2836(92)91031-j.
The hexagonal (H) and the cubic (Q223) phases of the systems dodecyltrimethylammonium chloride-water and palmitoyllysophosphatidy choline-water have been studied by X-ray scattering techniques. The signs of the reflections of phase H were determined by a systematic study as a function of the water content, those of phase Q223 were assessed using a pattern recognition approach based upon the axiom that the histograms of the electron density maps of phases Q223 and H, extrapolated to the same concentration and properly normalized in scale and shape, are very similar to each other. In the case of phase Q223, all the sign combinations (the phi-sets) compatible with the observed reflections were generated, and each of the corresponding histograms was compared with the histogram of the map of phase H. One novelty of this work is the use of a highly sensitive criterion to estimate the similarity of the histograms, namely the distance in the six-dimensional space of the moments [mean value of (delta rho)n]1/n, for 3 greater than or equal to n greater than or equal to 8. In the two systems, the use of this criterion has led to the unambiguous choice of one electron density map. The maps show that the structure of phase Q223 consists of disjointed micelles (of type I), belonging to two different classes: those of one class are quasi-spherical in shape and are centered at the points a, those of the other class are disc-shaped and are centred at the points c. The results of this work rule out a structure formed by a cage-like distribution of rods enclosing a set of quasi-spherical micelles and is consistent with previous proposals. This is the second example, after that of phase Q227, of a micellar cubic phases in lipid-containing systems; all the known examples of phase Q223 are of type I, those of phase Q227 of type II.
采用X射线散射技术研究了十二烷基三甲基氯化铵 - 水体系和棕榈酰溶血磷脂酰胆碱 - 水体系的六方相（H）和立方相（Q223）。通过系统研究作为水含量函数的相H的反射符号，利用基于以下公理的模式识别方法评估相Q223的反射符号：将相Q223和H的电子密度图的直方图外推到相同浓度并在比例和形状上适当归一化后，它们彼此非常相似。对于相Q223，生成了与观察到的反射兼容的所有符号组合（φ集），并将每个相应的直方图与相H的图的直方图进行比较。这项工作的一个新颖之处是使用了一种高度敏感的标准来估计直方图的相似性，即对于3≥n≥8，在矩[（δρ）n的平均值] 1 / n的六维空间中的距离。在这两个体系中，使用该标准导致明确选择了一个电子密度图。这些图表明，相Q223的结构由不相连的胶束（I型）组成，属于两个不同的类别：一类是准球形的，以点a为中心，另一类是盘状的，以点c为中心。这项工作的结果排除了由包围一组准球形胶束的棒状笼状分布形成的结构，并且与先前的提议一致。这是继Q227相之后，含脂体系中胶束立方相的第二个例子；所有已知的Q223相的例子都是I型，Q227相的例子是II型。
