title: Digital holographic microscopy of phase separation in multicomponent lipid membranes.
abstract: 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.
authors.affiliation: University of Zanjan, Department of Physics, Zanjan 45195-313, Iran.
authors.forename: Vahideh
authors.initials: V
authors.lastname: Farzam Rad
authors.affiliation: 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.
authors.forename: Ali-Reza
authors.initials: AR
authors.lastname: Moradi
authors.affiliation: University of Zanjan, Department of Physics, Zanjan 45195-313, IranbOptics Research Center, Institute for Advanced Studies in Basic Sciences, Zanjan 45137-66731, Iran.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Darudi
authors.affiliation: Marquette University, School of Dentistry, Milwaukee, Wisconsin 53233, United StateseUniversity of Oxford, Department of Engineering Science, Oxford OX1 3PJ, United Kingdom.
authors.forename: Lobat
authors.initials: L
authors.lastname: Tayebi
mesh_terms: D002784:Cholesterol / Q000737:chemistry; D004867:Equipment Design; D006696:Holography / Q000295:instrumentation / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008051:Lipid Bilayers / Q000737:chemistry*; D008853:Microscopy / Q000295:instrumentation / Q000379:methods*; D008954:Models, Biological; D010713:Phosphatidylcholines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010743:Phospholipids; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine