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.

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.

Synthesis, characterisation and liquid-crystalline phase transition studies on two higher homologues of 4O.m (m=14 and 16) series

2001 ◽  
Vol 709 ◽  
Author(s):  
C. Rama Chandra Prabhu ◽  
V.G.K.M. Pisipati
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Scanning Calorimetry ◽  
First Order ◽  
Smectic A ◽  
Phase Transition Temperatures ◽  
Crystalline Phase Transition ◽  
M 14 ◽  
Enthalpy Data ◽  
Transition Studies

ABSTRACTThe synthesis, characterization and phase transition studies of higher homologues of N(p-nbutoxybenzylidene)p-n-alkylanilines, Viz., 4O.m series (m=14 and 16) are carried out by thermal microscopy, differential scanning calorimetry and density. The compounds exhibit a phase variant of nematic and smectic-A. Density studies reveal a first order nature of IN transitions and a weak first order NA transitions. An estimate of pressure dependence of the phase transition temperatures using the volume and enthalpy data are presented. A comparison of these results with other reported results in nO.m and other compounds are presented.

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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