Roy Bibhisan, Satpathi Sagar, Gavvala Krishna, Koninti Raj Kumar, Hazra Partha
Department of Chemistry, Indian Institute of Science Education and Research (IISER) , Pune, 411008, Maharashtra, India.
J Phys Chem B. 2015 Sep 3;119(35):11721-31. doi: 10.1021/acs.jpcb.5b04370. Epub 2015 Aug 14.
Reverse hexagonal (HII) liquid crystalline material based on glycerol monooleate (GMO) is considered as a potential carrier for drugs and other important biomolecules due to its thermotropic phase change and excellent morphology. In this work, the dynamics of encapsulated water, which plays important role in stabilization and formation of reverse hexagonal mesophase, has been investigated by time dependent Stokes shift method using Coumarin-343 as a solvation probe. The formation of the reverse hexagonal mesophase (HII) and transformation to the L2 phase have been monitored using small-angle X-ray scattering and polarized light microscopy experiments. REES studies suggest the existence of different polar regions in both HII and L2 systems. The solvation dynamics study inside the reverse hexagonal (HII) phase reveals the existence of two different types of water molecules exhibiting dynamics on a 120-900 ps time scale. The estimated diffusion coefficients of both types of water molecules obtained from the observed dynamics are in good agreement with the measured diffusion coefficient collected from the NMR study. The calculated activation energy is found to be 2.05 kcal/mol, which is associated with coupled rotational-translational water relaxation dynamics upon the transition from "bound" to "quasi-free" state. The observed ∼2 ns faster dynamics of the L2 phase compared to the HII phase may be associated with both the phase transformation as well as thermotropic effect on the relaxation process. Microviscosities calculated from time-resolved anisotropy studies infer that the interface is almost ∼22 times higher viscous than the central part of the cylinder. Overall, our results reveal the unique dynamical features of water inside the cylinder of reverse hexagonal and inverse micellar phases.
基于甘油单油酸酯（GMO）的反六角（HII）液晶材料因其热致相变和优异的形态而被视为药物和其他重要生物分子的潜在载体。在这项工作中，使用香豆素 - 343作为溶剂化探针，通过时间相关斯托克斯位移法研究了在反六角中间相的稳定和形成中起重要作用的包封水的动力学。使用小角X射线散射和偏光显微镜实验监测了反六角中间相（HII）的形成以及向L2相的转变。REES研究表明在HII和L2系统中都存在不同的极性区域。反六角（HII）相内部的溶剂化动力学研究揭示了存在两种不同类型的水分子，它们在120 - 900 ps的时间尺度上表现出动力学。从观察到的动力学获得的两种类型水分子的估计扩散系数与从NMR研究收集的测量扩散系数高度一致。计算得到的活化能为2.05 kcal/mol，这与从“束缚”态到“准自由”态转变时的耦合旋转 - 平移水弛豫动力学相关。与HII相比，观察到L2相快约2 ns的动力学可能与相变以及弛豫过程中的热致效应有关。从时间分辨各向异性研究计算出的微粘度推断，界面的粘性几乎比圆柱体中心部分高约22倍。总体而言，我们的结果揭示了反六角相和反胶束相圆柱体内水的独特动力学特征。
