scholarly journals A computational study of lateral phase separation in biological membranes

2019 ◽  
Vol 35 (3) ◽  
pp. e3181 ◽  
Author(s):  
Vladimir Yushutin ◽  
Annalisa Quaini ◽  
Sheereen Majd ◽  
Maxim Olshanskii
Keyword(s):  
Phase Separation ◽  
Computational Study ◽  
Biological Membranes ◽  
Lateral Phase Separation

scholarly journals Adhesion-induced lateral phase separation in membranes

2000 ◽  
Vol 3 (3) ◽  
pp. 259-271 ◽  
Author(s):  
S. Komura ◽  
D. Andelman
Keyword(s):  
Phase Separation ◽  
Lateral Phase Separation

scholarly journals Non-axisymmetric shapes of biological membranes from locally induced curvature

2019 ◽  
Author(s):  
Yannick A. D. Omar ◽  
Amaresh Sahu ◽  
Roger A. Sauer ◽  
Kranthi K. Mandadapu
Keyword(s):  
Phase Separation ◽  
Cell Membrane ◽  
Viscous Flow ◽  
Lipid Bilayers ◽  
Biological Membranes ◽  
Rate Of Change ◽  
Computational Studies ◽  
Biological Processes ◽  
Resting Tension ◽  
Physical Phenomena

In various biological processes such as endocytosis and caveolae formation, the cell membrane is locally deformed into curved configurations. Previous theoretical and computational studies to understand membrane morphologies resulting from locally induced curvature are often limited to axisymmetric shapes, which severely restricts the physically admissible morphologies. Under the restriction of axisymmetry, past efforts predict that the cell membrane buds at low resting tensions and stalls at a flat pit at high resting tensions. In this work, we lift the restriction of axisymmetry by employing recent theoretical and numerical advances to understand arbitrarily curved and deforming lipid bilayers. Our non-axisymmetric morphologies reveal membrane morphologies which agree well with axisymmetric studies—however only if the resting tension of the membrane is low. When the resting tension is moderate to high, we show that (i) axisymmetric invaginations are unstable; and (ii) non-axisymmetric ridge-shaped structures are energetically favorable. We further study the dynamical effects resulting from the interplay between intramembrane viscous flow and induced curvature, and find the rate at which the locally induced curvature increases is a key determinant in the formation of ridges. In particular, we show that axisymmetric buds are favored when the induced curvature is rapidly increased, while non-axisymmetric ridges are favored when the curvature is slowly increased: The rate of change of induced curvature affects the intramembrane viscous flow of lipids, which can impede the membrane’s ability to transition into ridges. We conclude that the appearance of non-axisymmetric ridges indicates that axisymmetry cannot be generally assumed when understanding processes involving locally induced curvature. Our results hold potentially relevant implications for biological processes such as endocytosis, and physical phenomena like phase separation in lipid bilayers.

scholarly journals A computational study of phase separation in polymer solutions under a double quench

2021 ◽  
Author(s):  
Ehsan Hosseini
Keyword(s):  
Phase Separation ◽  
Polymer Solution ◽  
Spinodal Decomposition ◽  
Computational Study ◽  
Stable State ◽  
Thermal Quenching ◽  
Nucleation And Growth ◽  
Two Dimensions ◽  
Numerical Work ◽  
Binary Polymer

Polymer-dispersed liquid crystals (PDLCs) are a relatively new class of materials used for many applications ranging from switchable windows to projection displays. PDLSs are formed by spinodal decomposition induced by thermal quenching or polymerization. The objective of the present study is to introduce a new mechanism of phase separation in a binary polymer solution and develop a mathematical model and computer simulation to describe the phase separation during the early and intermediate stages of nucleation and growth and spinodal decomposition induced by thermal double quenching. The growth equilibrium limits of phase separation as well as phase transition are calculated by taking into consideration the Flory-Huggins theory for the free energy of mixing. A two step quench is modeled using Cahn-Hilliard theory for asymmetric binary polymer solution which is quenched from a stable state in the one-phase region to a metastable region where nucleation and growth occurs. The solution is allowed to coarsen for different time periods before a second quench was applied to a point further inside the phase diagram. The numerical results in two dimensions replicate the experimental and numerical work that has been recently done and published.

scholarly journals A computational study of phase separation in polymer solutions under a double quench

2021 ◽  
Author(s):  
Ehsan Hosseini
Keyword(s):  
Phase Separation ◽  
Polymer Solution ◽  
Spinodal Decomposition ◽  
Computational Study ◽  
Stable State ◽  
Thermal Quenching ◽  
Nucleation And Growth ◽  
Two Dimensions ◽  
Numerical Work ◽  
Binary Polymer

Polymer-dispersed liquid crystals (PDLCs) are a relatively new class of materials used for many applications ranging from switchable windows to projection displays. PDLSs are formed by spinodal decomposition induced by thermal quenching or polymerization. The objective of the present study is to introduce a new mechanism of phase separation in a binary polymer solution and develop a mathematical model and computer simulation to describe the phase separation during the early and intermediate stages of nucleation and growth and spinodal decomposition induced by thermal double quenching. The growth equilibrium limits of phase separation as well as phase transition are calculated by taking into consideration the Flory-Huggins theory for the free energy of mixing. A two step quench is modeled using Cahn-Hilliard theory for asymmetric binary polymer solution which is quenched from a stable state in the one-phase region to a metastable region where nucleation and growth occurs. The solution is allowed to coarsen for different time periods before a second quench was applied to a point further inside the phase diagram. The numerical results in two dimensions replicate the experimental and numerical work that has been recently done and published.

scholarly journals Phase Diagram of Purified CNS Myelin Reveals Continuous Transformation between Expanded and Compacted Lamellar States

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 670
Author(s):  
Julio M. Pusterla ◽  
Emanuel Schneck ◽  
Rafael G. Oliveira
Keyword(s):  
Phase Diagram ◽  
Phase Separation ◽  
Isothermal Transformation ◽  
Phase Behaviour ◽  
Apparent Difference ◽  
X Ray Diffraction ◽  
Lateral Phase Separation ◽  
Diffraction Peaks ◽  
Low Ionic Strength ◽  
Detergent Resistant Membrane

Purified myelin membranes (PMMs) are the starting material for biochemical studies, from individual components up to the isolation of detergent-resistant membrane (DRM) fractions or detergent-insoluble glycosphingolipid (DIG) fractions, which are commonly believed to resemble physiological lipid rafts. The normal DIG isolation protocol involves the extraction of lipids under moderate cooling. The isolation of PMMs also involves the cooling of myelin as well as exposure to low ionic strength (IS). Here, we addressed the combined influence of cooling and IS on the structure of PMMs. The phase behaviour was investigated by small angle X-ray diffraction. Analysis of the diffraction peaks revealed the lamellar periodicity ( d ), the number of periodically correlated bilayers ( N ), and the relatives fractions of each phase. Departure from physiological conditions induced a phase separation in myelin. The effect of monovalent and divalent ions was also compared at equivalent IS, showing a differential effect, and phase diagrams for both ion types were established—Ca2+ induced the well-known over-compacted phase, but additionally we also found an expanded phase at low IS. Na+ promoted phase separation, and also induced over-compaction at sufficiently high IS. Finally, exploring the whole phase diagram, we found evidence for the direct isothermal transformation from the expanded to the compacted phase, suggesting that both phases could in fact originate from the identical primary lateral phase separation, whereas the apparent difference lies in the inter-bilayer interaction that is modulated by the ionic milieu.

Calcium-induced lateral phase separation in phosphatidic acid/phosphatidylcholine monolayers as revealed by fluorescence microscopy

Biochemistry ◽  
1988 ◽  
Vol 27 (9) ◽  
pp. 3433-3437 ◽  
Author(s):  
Kari K. Eklund ◽  
Jorma Vuorinen ◽  
Jukka Mikkola ◽  
Jorma A. Virtanen ◽  
Paavo K. J. Kinnunen
Keyword(s):  
Phase Separation ◽  
Fluorescence Microscopy ◽  
Phosphatidic Acid ◽  
Lateral Phase Separation

Lateral and Vertical Phase Separation Control of Thin-film Structures for Photovoltaics

2001 ◽  
Vol 665 ◽  
Author(s):  
A. C. Arias ◽  
J. D. MacKenzie ◽  
N. Corcoran ◽  
R. H. Friend
Keyword(s):  
Phase Separation ◽  
Spin Coating ◽  
Solution Viscosity ◽  
Separation Control ◽  
Nanometer Scale ◽  
Length Scale ◽  
Photovoltaic Devices ◽  
Photovoltaic Properties ◽  
Lateral Phase Separation ◽  
Photoluminescence Efficiency

ABSTRACTInvestigations on microscopic and photovoltaic properties of polyfluorene blends are presented here. The length scale of lateral phase separation is manipulated by control of solvent evaporation conditions. Photoluminescence efficiency measurements show that charge transfer is more effective in blends phase separated on the nanometer scale. Vertically segregated structures are obtained by a combination of solution viscosity and spin coating conditions. The external quantum efficiency of photovoltaic devices fabricated with vertically segregated blend is found to be 4 times higher than that of devices made with laterally segregated blends.

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