Pebay-Peyroula E, Dufourc E J, Szabo A G
Institut Laue Langevin, Grenoble, France.
Biophys Chem. 1994 Dec;53(1-2):45-56. doi: 10.1016/0301-4622(94)00075-1.
Neutron scattering experiments have been performed on oriented dipalmitoylphosphatidylcholine (DPPC) bilayers containing diphenylhexatriene (DPH) or its trimethylammonium analog (TMA-DPH). DPH and TMA-DPH were either protonated or deuterated in one of the phenyl rings which afforded by using proton-deuterium contrast methods the location of these fluorescent probes in the model membrane. Both probes exhibit bimodal distributions in DPPC. The position, population and orientation in the two sites vary depending upon the physical state of the bilayer (gel or fluid) and the presence or absence of the TMA group. In gel (L beta') phase lipids DPH is located close and parallel to the bilayer surface (site I) and near the bilayer center, oriented at approximately 30 degrees with respect to the normal to the surface (site II). On going to the fluid (L alpha) phase, a distribution of orientations around the parallel to the surface is only observed for site II. Orientation of DPH in site I is unchanged. In the gel phase TMA-DPH is found in a position close and parallel to the bilayer surface (site I) and in a position (site II) oriented at an angle of approximately 25 degrees with respect to the bilayer normal, with the trimethylammonium group anchored in the head group domain. On going to the fluid phase there is a change in molecular orientation of each of the sites. In site I the molecule penetrates deeper in the bilayer and adopts a approximately 20 degrees tilt with respect to the surface, with an orientational distribution of +/- 10 degrees. In site II the molecule becomes perpendicular to the membrane surface. Changes in population of sites, both with DPH and TMA-DPH, are observed on going from low to high temperatures. They are however difficult to quantitate due to experimental conditions. The H2O-2H2O exchange experiments afforded an estimate of the water layer thickness as well as the maximum penetration of water into the interior of the bilayer.
已对含有二苯基己三烯（DPH）或其三甲铵类似物（TMA-DPH）的取向二棕榈酰磷脂酰胆碱（DPPC）双层膜进行了中子散射实验。DPH和TMA-DPH在其中一个苯环上进行了质子化或氘代，通过质子-氘对比度方法确定了这些荧光探针在模型膜中的位置。两种探针在DPPC中均呈现双峰分布。两个位点的位置、数量和取向取决于双层膜的物理状态（凝胶态或流体态）以及TMA基团的存在与否。在凝胶（Lβ'）相脂质中，DPH位于靠近双层膜表面且与之平行的位置（位点I）以及双层膜中心附近，相对于膜表面法线成约30度取向（位点II）。进入流体（Lα）相时，仅在位点II观察到围绕平行于表面方向的取向分布。位点I中DPH的取向不变。在凝胶相中，TMA-DPH位于靠近双层膜表面且与之平行的位置（位点I）以及相对于双层膜法线成约25度角取向的位置（位点II），三甲铵基团锚定在头部基团区域。进入流体相时，每个位点的分子取向都会发生变化。在位点I中，分子在双层膜中穿透更深，相对于表面倾斜约20度，取向分布为±10度。在位点II中，分子变得垂直于膜表面。从低温到高温时，观察到DPH和TMA-DPH在位点数量上的变化。然而，由于实验条件的原因，很难对其进行定量。H2O-2H2O交换实验估计了水层厚度以及水进入双层膜内部的最大深度。
