scholarly journals The Two Faces of the Liquid Ordered Phase

2021 ◽  
Author(s):  
Itay Schachter ◽  
Riku Paananen ◽  
Balazs Fabian ◽  
Piotr Jurkiewicz ◽  
Matti Javanainen
Keyword(s):  
Molecular Dynamics ◽  
Differential Scanning Calorimetry ◽  
Low Temperatures ◽  
High Mobility ◽  
Membrane Properties ◽  
Scanning Calorimetry ◽  
Lipid Mixtures ◽  
Liquid Ordered ◽  
Raft Domains ◽  
Dynamics Simulations

The coexistence of liquid ordered Lo and liquid disordered Ld phases in synthetic and plasma membrane-derived vesicles serves as a model for biomembrane heterogeneity. However, the connection between the structures of microscopic phases present in vesicles at low temperatures and the tiny ordered "raft" domains of biomembranes at body temperature is unclear. To study the Lo phase structure across temperatures, we performed atomistic molecular dynamics simulations, differential scanning calorimetry, and fluorescence spectroscopy on the Lo phase in binary and ternary lipid mixtures. Our results reveal an Lo phase with highly ordered and hexagonally packed clusters of saturated lipid chains at low temperatures. These clusters melt upon heating, and numerous membrane properties reflect this transition as two regimes with different temperature dependence. Still, the transition between the regimes is continuous, and they both match the description of the Lo phase with high order and relatively high mobility. Our findings question the use of vesicles displaying Lo–Ld coexistence as models for heterogeneity in cellular membranes, as they likely correspond to different molecular organizations.

scholarly journals Local Structuring of Diketopyrrolopyrrole (DPP)-based Oligomers from Molecular Dynamics Simulations

2021 ◽  
Author(s):  
Maryam Reisjalali ◽  
J. Javier Burgos-Marmol ◽  
Rex Manurung ◽  
Alessandro Troisi
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
High Mobility ◽  
Semiconducting Polymers ◽  
Microscopic Structure ◽  
Dynamics Simulations

The microscopic structure of high mobility semiconducting polymers is known to be essential for their performance but it cannot be easily deduced from the available experimental data. A series of...

The Crystal Structures at 10 K of the Trigonal Salts KMIII(NH3)6(ClO4)2Cl2, MIII = Os and Cr, and the Possibility of Phase Transitions

1999 ◽  
Vol 52 (3) ◽  
pp. 219 ◽  
Author(s):  
Philip A. Reynolds ◽  
Brian N. Figgis ◽  
Alexander N. Sobolev
Keyword(s):  
Differential Scanning Calorimetry ◽  
Transition Temperature ◽  
Crystal Structures ◽  
Low Temperatures ◽  
Simple Structure ◽  
Alkali Metal Cations ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Threefold Axis ◽  
X Ray

The crystal structures of KOs(NH3)3(ClO4)2Cl2 and KCr(NH3)6(ClO4)2Cl2 were determined at 10 K by X-ray diffraction, and for the osmium salt also at 293 K. At 293 K the osmium salt is trigonal, space group R 3m, with the same simple structure as others of this class of double salt. At 10 K, in agreement with previous radius ratio predictions, both crystals are best described as remaining R 3m. All previously studied members, with larger alkali metal cations, are twinned R 3 at low temperatures, with small, symmetry-breaking rotations of the hexaamminemetal(III) and perchlorate ions about the threefold axis. Differential scanning calorimetry on CsRu(NH3)6(ClO4)2Cl2 suggests that the R 3m to R 3 change is very extended in temperature with only a small discontinuity at the transition temperature.

scholarly journals Regimes of Complex Lipid Bilayer Phases Induced by Cholesterol Concentration in MD Simulation

2018 ◽  
Author(s):  
George A. Pantelopulos ◽  
John E. Straub
Keyword(s):  
Phase Separation ◽  
Cholesterol Concentration ◽  
Lipid Domains ◽  
Lipid Mixture ◽  
Knowledge Models ◽  
Lipid Mixtures ◽  
Mixture Phase ◽  
Liquid Ordered ◽  
Dynamics Simulations ◽  
And Function

AbstractCholesterol is essential to the formation of phase separated lipid domains in membranes. Lipid domains can exist in different thermodynamic phases depending on the molecular composition, and play significant roles in determining structure and function of membrane proteins. We investigate the role of cholesterol in the structure and dynamics of ternary lipid mixtures displaying phase separation using Molecular Dynamics simulations, employing a physiologically-relevant span of cholesterol concentration. We find that cholesterol can induce formation of three regimes of phase behavior, I) miscible liquid disordered bulk, II) phase separated, domain registered coexistence of liquid disordered and liquid ordered and domains, and III) phase separated, domain-anti-registered coexistence of liquid-disordered and newly-identified nanoscopic gel domains composed of cholesterol threads we name “cholesterolic gel” domains. These findings are validated and discussed in the context of current experimental knowledge, models of cholesterol spatial distributions, and models of ternary lipid mixture phase separation.

scholarly journals Cardiolipin-Dependent Properties of Model Mitochondrial Membranes from Molecular Dynamics Simulations

2019 ◽  
Author(s):  
Blake A. Wilson ◽  
Arvind Ramanathan ◽  
Carlos F. Lopez
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Negative Curvature ◽  
Structural Features ◽  
Barth Syndrome ◽  
Biophysical Properties ◽  
Mitochondrial Membranes ◽  
Lipid Mixtures ◽  
Mitochondrial Functions ◽  
Dynamics Simulations

ABSTRACTCardiolipin is a unique anionic lipid found in mitochondrial membranes where it contributes to various mitochondrial functions, including metabolism, mitochondrial membrane fusion/fission dynamics, and apoptosis. Dysregulation of cardiolipin synthesis and remodeling have also been implicated in several diseases, such as diabetes, heart disease and Barth Syndrome. Although cardiolipin’s structural and dynamic roles have been extensively studied in binary mixtures with other phospholipids, the biophysical properties of cardiolipin in ternary lipid mixtures are still not well resolved. Here, we used molecular dynamics simulations to investigate the cardiolipin-dependent properties of ternary lipid bilayer systems that mimic the major components of mitochondrial membranes. We found that changes to cardiolipin concentration only resulted in minor changes to bilayer structural features, but that the lipid diffusion was significantly affected by those alterations. We also found that cardiolipin position along the bilayer surfaces correlated to negative curvature deflections, consistent with the induction of negative curvature stress in the membrane monolayers. This work contributes to a foundational understanding of the role of CL in altering the properties in ternary lipid mixtures composed of the major mitochondrial phospholipids, providing much needed insights to help understand how cardiolipin concentration modulates the biophysical properties of mitochondrial membranes.

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