The effect of cholesterol on the interaction of glucagon with the gel state of dimyristoylphosphatidylcholine

1980 ◽  
Vol 58 (10) ◽  
pp. 859-864 ◽  
Author(s):  
Richard M. Epand
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Light Scattering ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Binding ◽  
Starting Material ◽  
Scatchard Analysis ◽  
Lipid Interactions ◽  
Fluorescence Measurements

Cholesterol has a large effect on the binding of glucagon to dimyristoylphosphatidylcholine (DMPC) and to dipalmitoylphosphatidylcholine (DPPC). At cholesterol concentrations of 20 mol% or greater there is virtually no interaction of glucagon with phospholipid. Glucagon can, however, solubilize DMPC or DPPC with 10% cholesterol. In the case of DPPC the solubilized lipid is depleted of cholesterol relative to the starting material. These results suggest that glucagon excludes cholesterol from its surroundings.It is shown from solubility, light scattering, and glucagon fluorescence measurements that the glucagon–DMPC complex containing 10% cholesterol is stable only in the region of the phase transition temperature. Scatchard analysis of lipid binding to glucagon indicates a decrease in the amount of bound lipid below 22 °C or above 24 °C. The effect of the phase transition on the interaction of glucagon with lipids is compared with that found for other membrane proteins. Several aspects of the effect of cholesterol on glucagon–lipid interactions are analogous to effects which have been observed with serum apolipoproteins.

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

scholarly journals Liposomal Encapsulation of Oleuropein and an Olive Leaf Extract: Molecular Interactions, Antioxidant Effects and Applications in Model Food Systems

2020 ◽  
Author(s):  
Rodrigo González-Ortega ◽  
Luka Šturm ◽  
Mihaela Skrt ◽  
Carla Daniela Di Mattia ◽  
Paola Pittia ◽  
...  
Keyword(s):  
Phase Transition ◽  
Lipid Peroxidation ◽  
Transition Temperature ◽  
Liquid Phase ◽  
Phase Transition Temperature ◽  
Leaf Extract ◽  
Olive Leaf ◽  
Liquid Phase Transition ◽  
Olive Leaf Extract ◽  
Fluorescence Measurements

Abstract The influence of actively/passively encapsulated oleuropein on DPPC liposomes thermal and structural properties, and its antioxidant capacity against lipid peroxidation were investigated. Also, an oleuropein-rich olive leaf extract was encapsulated in soy phosphatidylcholine (PL-90 g) and incorporated in model and commercial drinks. Oleuropein induced a concentration-dependent broadening and splitting of the gel-to-liquid phase transition temperature. Fluorescence measurements revealed a fluidizing effect on liposomes below their gel-to-liquid phase transition temperature, and a higher lipid ordering above, especially to active encapsulation. Oleuropein also showed an antioxidant effect against lipid peroxidation in PL-90 g liposomes. PL-90 g Liposomes with olive leaf extract showed a mean diameter of 405 ± 4 nm and oleuropein encapsulation efficiency of 34% and delayed oleuropein degradation at pH 2.0 and 2.8 model drinks. In conclusion, greater effects were observed on the structure and fluidity of DPPC liposomes when oleuropein was actively encapsulated, while its incorporation into acidic foods in encapsulated form could enhance its stability.

Nonequilibrium Fluctuations of Light Scattering Intensity in the Neighborhood of the Phase Transition Temperature

2020 ◽  
Vol 128 (1) ◽  
pp. 74-77
Author(s):  
A. N. Alekseev ◽  
L. Yu. Vergun ◽  
Yu. F. Zabashta ◽  
V. I. Kovalchuk ◽  
M. M. Lazarenko ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Light Scattering ◽  
Phase Transition Temperature ◽  
Nonequilibrium Fluctuations ◽  
Scattering Intensity ◽  
Light Scattering Intensity

scholarly journals Study of physical properties of a ferrimagnetic spinel Cu1.5Mn1.5O4: spin dynamics, magnetocaloric effect and critical behavior

RSC Advances ◽  
2021 ◽  
Vol 11 (41) ◽  
pp. 25664-25676
Author(s):  
Abir Hadded ◽  
Jalel Massoudi ◽  
Sirine Gharbi ◽  
Essebti Dhahri ◽  
A. Tozri ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Physical Properties ◽  
Magnetocaloric Effect ◽  
Phase Transition Temperature ◽  
Magnetic Phase Transition ◽  
Critical Behavior ◽  
Magnetic Phase ◽  
Spin Dynamics ◽  
Critical Behaviour

The present work reports a detailed study of the spin dynamics, magnetocaloric effect and critical behaviour near the magnetic phase transition temperature, of a ferrimagnetic spinel Cu1.5Mn1.5O4.

scholarly journals Modulating the phase transition temperature of giant magnetocaloric thin films by ion irradiation

2017 ◽  
Vol 1 (6) ◽  
Author(s):  
S. Cervera ◽  
M. Trassinelli ◽  
M. Marangolo ◽  
C. Carrétéro ◽  
V. Garcia ◽  
...  
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Ion Irradiation
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