University of Zanjan, Department of Physics, Zanjan 45195-313, Iran.
University of Zanjan, Department of Physics, Zanjan 45195-313, IranbOptics Research Center, Institute for Advanced Studies in Basic Sciences, Zanjan 45137-66731, IrancBilkent University, Department of Physics, Cankaya, Ankara 06800, Turkey.
J Biomed Opt. 2016 Dec 1;21(12):126016. doi: 10.1117/1.JBO.21.12.126016.
Lateral in-homogeneities in lipid compositions cause microdomains formation and change in the physical properties of biological membranes. With the presence of cholesterol and mixed species of lipids, phospholipid membranes segregate into lateral domains of liquid-ordered and liquid-disordered phases. Coupling of two-dimensional intralayer phase separations and interlayer liquid-crystalline ordering in multicomponent membranes has been previously demonstrated. By the use of digital holographic microscopy (DHMicroscopy), we quantitatively analyzed the volumetric dynamical behavior of such membranes. The specimens are lipid mixtures composed of sphingomyelin, cholesterol, and unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine. DHMicroscopy in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes, three-dimensional information on the morphology variation of lipid stacks at arbitrary time scales is obtained. Moreover, the thickness distribution of the object at demanded axial planes can be obtained by numerical focusing. Our results show that the volume evolution of lipid domains follows approximately the same universal growth law of previously reported area evolution. However, the thickness of the domains does not alter significantly by time; therefore, the volume evolution is mostly attributed to the changes in area dynamics. These results might be useful in the field of membrane-based functional materials.
脂质组成的横向不均匀性导致微区的形成，并改变生物膜的物理性质。在胆固醇和混合脂质物种的存在下，磷脂膜会分离成有序相和无序相的侧向畴。先前已经证明了具有双层层内相分离和层间液晶有序性的多组分膜的耦合。通过使用数字全息显微镜（DHMicroscopy），我们定量分析了这种膜的体积动力学行为。这些标本是由鞘磷脂、胆固醇和不饱和磷脂 1,2-二油酰基-sn-甘油-3-磷酸胆碱组成的脂质混合物。透射模式下的 DHMicroscopy 是定量可视化相物体的有效工具。通过得出相关的相位变化，可以获得脂质堆积在任意时间尺度上的形态变化的三维信息。此外，通过数值聚焦可以获得所需轴向平面上物体的厚度分布。我们的结果表明，脂质域的体积演化大致遵循先前报道的面积演化的相同普遍生长规律。然而，域的厚度并没有随时间发生显著变化；因此，体积演化主要归因于面积动力学的变化。这些结果可能在基于膜的功能材料领域有用。
