Interaction of sporidesmin, a mycotoxin from Pithomyces chartarum, with lipid bilayers

1993 ◽  
Vol 13 (4) ◽  
pp. 233-243 ◽  
Author(s):  
G. C. Upreti ◽  
M. K. Jain
Keyword(s):  
Phase Transition ◽  
Cell Membrane ◽  
Lipid Bilayers ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Glycerol Backbone ◽  
Pancreatic Phospholipase ◽  
Pancreatic Phospholipase A2 ◽  
Liquid Crystalline Phases ◽  
Hydrophobic Molecule

Sporidesmin, a mycotoxin from Pithomyces chartarum is a hydrophobic molecule. It can therefore be easily incorporated in the cell membrane, where it is likely to cause changes in the bilayer organization and the properties of membrane proteins. In order to understand the redox behaviour of sporidesmin in a hydrophobic environment, we have investigated the effects of oxidized and reduced sporidesmin on the phase transition properties of bilayers and on the susceptibility of bilayers to pancreatic phospholipase A2 (PLA2). The changes induced by sporidesmin in the thermotropic phase transition profiles of dimyristoyl-sn-3-phosphatidyl choline (DMPC) bilayers were similar to those caused by solutes known to localize in the glycerol-backbone region of the lipid bilayer, suggesting a similar localization for oxidized and reduced sporidesmin. Neither form of toxin disrupt the bilayer or membrane organization even at relatively high mole fractions. At concentrations <10 mole% both forms partitioned equally well in the gel and liquid-crystalline phases, whereas at higher concentrations (≈30 mole%) reduced sporidesmin is preferentially localized in the liquid-crystalline phase. These effects of sporidesmin on the phase properties of DMPC vesicles were also reported by the fluorescence behavior of 10-pyrenedecanoic acid (PDA). The effects of oxidized and reduced sporidesmins on PLA2 kinetics are consistent with their ability to perturb bilayer organisation.

Temperature Dependence of the Phospholipids Bilayers Stability, Studied by FTIR Spectroscopy

2008 ◽  
Vol 59 (3) ◽  
pp. 356-359 ◽  
Author(s):  
Feride Severcan ◽  
Catalin Agheorghiesei ◽  
Dana-Ortansa Dorohoi
Keyword(s):  
Phase Transition ◽  
Lipid Bilayers ◽  
Liquid Crystalline ◽  
Correlation Spectroscopy ◽  
Liquid Crystalline Phases ◽  
Hydrocarbon Chains ◽  
Acyl Chains ◽  
Stretching Vibrations ◽  
Two Phases ◽  
Spectral Ranges

The temperature induced modifications in the lipid bilayers in water were studied by using 2D-FTIR Correlation Spectroscopy. The spectral range analysed in this paper corresponds to symmetric and asymmetric stretching vibrations of the �CH2 groups from the acyl chains of DPPC. Autocorrelation peaks at 2916 cm-1 and 2848.5 cm-1 and asynchrone modifications in the spectral ranges 2916-3000 cm-1 and 2848-3000 cm-1 were evidenced. The revealed modifications indicate changes in the conformers of the hydrocarbon chains in the phase transition from the gel to liquid crystalline phases, as well as the variations in the concentration of the two phases with temperature increasing.

Hydrolysis of phosphatidylcholine liposomes by lysosomal phospholipase A is maximal at the phase transition temperature of the lipid substrate

1985 ◽  
Vol 5 (6) ◽  
pp. 477-482 ◽  
Author(s):  
Michel Vandenbranden ◽  
Georges De Gand ◽  
Robert Brasseur ◽  
Fabienne Defrise-Quertain ◽  
Jean-Marie Ruysschaert
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Temperature Characteristic ◽  
Phosphatidylcholine Liposomes ◽  
Pancreatic Phospholipase ◽  
Pancreatic Phospholipase A2 ◽  
Rate Of Hydrolysis ◽  
Structural Analogy ◽  
Hydrolysis Of ◽  
Crystalline Phase Transition

We have measured the rate of hydrolysis of liposomes made of DL-α-dipalmitoylphosphatidylcholine (DPPC) and L-α-dimyristoylphosphatidylcholine by a soluble fraction of highly purified lysosomes isolated from rat liver. Phospholipids are hydrolyzed into lysophospho-lipids and fatty acids at a rate which is maximal near the temperature characteristic of the gel to liquid crystalline phase transition of the lipid bilayer. This strong influence of the physical properties of the substrate on the enzyme activity suggests a structural analogy between the lysosomal phospholipases of the A type (EC 3.1.1.32 and EC 3.1.1.4) and the pancreatic phospholipase A2.

Characterization of some mesogenic alkyl 1-thioglycosides

2002 ◽  
Vol 80 (8) ◽  
pp. 1162-1165 ◽  
Author(s):  
B Henrissat ◽  
G K Hamer ◽  
M G Taylor ◽  
R H Marchessault
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Solid State ◽  
Solid State Nmr ◽  
Liquid Crystalline ◽  
Liquid Crystal Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Liquid Crystalline Phases

A series of dodecyl 1-thio-β-D-glycosides has been synthesized and characterized (DSC, NMR, CP MAS, X-ray diffraction) as possible new marking materials with liquid-crystalline properties. These compounds undergo solid to liquid crystal phase transitions at various temperatures, which depend on the nature of the carbohydrate part of the structure. Their liquid-crystalline phases show extreme shear thinning behaviour.Key words: liquid crystal, powder X-ray diffraction, phase transition, thioglycoside, solid-state NMR, marking material

Columnar liquid crystals derived from long-chain carboxylates of transition metal ions

1990 ◽  
Vol 330 (1610) ◽  
pp. 109-116 ◽  
Keyword(s):  
Phase Transition ◽  
Fatty Acids ◽  
Magnetic Moment ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Hexagonal Lattice ◽  
Transition Metal Ions ◽  
Liquid Crystalline Phase ◽  
Zero Field ◽  
Metal Metal

Copper 11 complexes of the fatty acids exhibit a thermotropic liquid crystalline phase of the columnar type. X-ray diffraction studies of this mesophase indicate that the spine of a column is made of regularly stacked dicopper tetracarboxylate cores, which are surrounded by disordered, liquid-like alkyl chains. In turn, the column axes occupy the nodes of a two-dimensional hexagonal lattice. Examination of the local environment of the copper atoms by Cu Ka 2 EXAFS spectroscopy reveals insignificant changes in bond lengths within the binuclear core upon the transition from the lamellar crystalline phase to the columnar mesophase. However, a slight, but sharp, decrease of the magnetic moment of the dicopper unit is observed at the solid-mesophase transition temperature (A/4eff « —0.04 ■ The columnar mesophase, and the crystalline phase alike, obey a Bleaney-Bowers relation. The singlet-triplet gap is higher in the former ( -2J = 310-330 cm -1 against 290-300 cm -1 ). Dirhodium 11.11 complexes of selected fatty acids were prepared, and their thermal behaviour was investigated. They exhibit the same thermotropic columnar mesophase as their Cu 11 congeners, reflecting the presence of isostructural dimetallic cores in both series. The metal-metal single bond that is present in these dirhodium 11,11 mesogens is Raman active (iv Rh _ Rh - 350 cm -1 ) ; it is a potential probe of the change in molecular and supramolecular structures of this class of compounds at their phase transition. Diruthenium 11.11 complexes of fatty acids were obtained by Cr 11 reduction of the mixed-valence chlorodiruthenium 11.111 tetrabutyrate, followed by ligand exchange with the appropriate carboxylic acid. Magnetic susceptibility studies indicate that these diruthenium 11.11 carboxylates have an M 5 = 0 ground state and a thermally accessible M 8 = ± 1 excited state, suggesting a zero-field split ( D = 300 cm -1 } a 2 7i 4 5 2 (5*7t*) 4 configuration. The formation of a columnar liquid-crystalline phase is reflected by a sharp increase in the magnetic moment of these complexes at the phase transition (A ju,ef{% +0

Mixed-dimer formation in binary systems of 4-substituted benzoic acids and structure considerations

2008 ◽  
Vol 86 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Maren Roman ◽  
Annett Kaeding-Koppers ◽  
Peter Zugenmaier
Keyword(s):  
Benzoic Acid ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Binary Systems ◽  
Benzoic Acids ◽  
Dimer Formation ◽  
Crystalline Phases ◽  
Cholesteric Phase ◽  
Liquid Crystalline Phases ◽  
Substituted Benzoic Acids

The phase behavior of binary systems of 4-substituted benzoic acids is governed by the formation of mixed dimers. This study was conducted to determine the effect of the components’ structural difference on mixed-dimer formation in crystalline and liquid-crystalline phases. The phase diagrams of two systems, with 4-[(S)-(–)-2-methylbutoxy]benzoic acid (MBOBA) as one component and 4-(hex-5-enoxy)benzoic acid (HOBA) and 4-(dec-9-enoxy)benzoic acid (DOBA), respectively, as the second component, were determined by differential scanning calorimetry, polarized-light microscopy, and X-ray diffraction. The MBOBA-HOBA system exhibited a cholesteric phase, two solid solutions, and above 58 °C for compositions between 40 and 80 mol% HOBA a crystalline phase of mixed dimers. The MBOBA-DOBA system showed a crystalline phase of mixed dimers at all compositions, a cholesteric phase, and a twisted smectic C phase, which was dominated by mixed dimers at 60 and 70 mol% DOBA. We conclude that liquid-crystalline phases are generally dominated by mixed dimers, but in crystalline phases the formation of mixed dimers is promoted by a greater difference in molecular structure. The crystal structure of two of the pure compounds MBOBA and DOBA and comparable compounds have been determined for an evaluation of the arrangements of the molecules in the crystal and liquid-crystalline state.Key words: benzoic acid, crystal arrangement, phase diagrams, liquid crystal.

Liquid Crystalline Phase Transition Induces Spin Crossover in a Polyelectrolyte Amphiphile Complex

2009 ◽  
Vol 131 (8) ◽  
pp. 2934-2941 ◽  
Author(s):  
Yves Bodenthin ◽  
Guntram Schwarz ◽  
Zbigniew Tomkowicz ◽  
Thomas Geue ◽  
Wolfgang Haase ◽  
...  
Keyword(s):  
Phase Transition ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Spin Crossover ◽  
Liquid Crystalline Phase ◽  
Crystalline Phase Transition
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