Chen Xiaodong, Wiehle Susanne, Weygand Markus, Brezesinski Gerald, Klenz Ute, Galla Hans-Joachim, Fuchs Harald, Haufe Günter, Chi Lifeng
Physikalisches Institut, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany.
J Phys Chem B. 2005 Oct 27;109(42):19866-75. doi: 10.1021/jp054788p.
A single-chain fatty acid methyl ester, racemic anti-3-fluoro-2-hydroxyeicosanoic acid methyl ester (beta-FHE), forms an unconventional air-stable interdigitated bilayer at the air-water interface. The interdigitated bilayer transferred onto solid substrate by the Langmuir-Blodgett (LB) technique keeps air-stable without any substrate modification or protein inclusion. There are two visible plateaus in the surface pressure-molecular area (pi-A) isotherms of beta-FHE Langmuir film during continuous compression. According to Brewster angle microscopy (BAM), grazing incidence X-ray diffraction (GIXD), X-ray reflectivity (XR), fluorescence microscopy (FM), and atomic force microscopy (AFM) measurements, the first plateau is attributed to the coexistence of liquid expanded (LE) and liquid condensed (LC) phases in the monolayer, while the second plateau is interpreted as the transition from LC monolayer to interdigitated bilayer. The coupling between tilt and curvature associated with the packing mismatch between headgroup and chain gives rise to buckling and folding of the monolayer, leading to the transition of the LC monolayer to a bilayer structure. The diffusion-limited aggregation (DLA) model is applied to describe the formation of the fractal structures of the bilayer as observed in the second plateau. In addition, the transition between monolayer and bilayer is reversible. The present works are interesting for understanding biological processes, for example, the behavior of lung surfactants.
一种单链脂肪酸甲酯，即外消旋反式-3-氟-2-羟基二十烷酸甲酯（β-FHE），在气-水界面形成了一种非常规的空气稳定型叉指双层结构。通过朗缪尔-布洛杰特（LB）技术转移到固体基质上的叉指双层在没有任何基质修饰或蛋白质包入的情况下保持空气稳定性。在连续压缩过程中，β-FHE朗缪尔膜的表面压力-分子面积（π-A）等温线有两个明显的平台。根据布鲁斯特角显微镜（BAM）、掠入射X射线衍射（GIXD）、X射线反射率（XR）、荧光显微镜（FM）和原子力显微镜（AFM）测量，第一个平台归因于单分子层中液体扩张（LE）相和液体凝聚（LC）相的共存，而第二个平台被解释为从LC单分子层到叉指双层的转变。与头基和链之间的堆积失配相关的倾斜和曲率之间的耦合导致了单分子层的屈曲和折叠，从而导致LC单分子层向双层结构的转变。应用扩散限制聚集（DLA）模型来描述在第二个平台中观察到的双层分形结构的形成。此外，单分子层和双层之间的转变是可逆的。目前的工作对于理解生物过程，例如肺表面活性剂的行为，具有重要意义。
