Application of the Smoluchowski equation with a source term to the model of lipid pore formation during a phase transition

BIOPHYSICS ◽  
2016 ◽  
Vol 61 (6) ◽  
pp. 936-941 ◽  
Author(s):  
A. A. Anosov ◽  
A. A. Sharakshane ◽  
E. Yu. Smirnova ◽  
O. Yu. Nemchenko
Keyword(s):  
Phase Transition ◽  
Pore Formation ◽  
Source Term ◽  
Smoluchowski Equation ◽  
Lipid Pore

scholarly journals The Effect of the Osmotically Active Compound Concentration Difference on the Passive Water and Proton Fluxes across a Lipid Bilayer

2021 ◽  
Vol 22 (20) ◽  
pp. 11099
Author(s):  
Magdalena Przybyło ◽  
Dominik Drabik ◽  
Joanna Doskocz ◽  
Aleš Iglič ◽  
Marek Langner
Keyword(s):  
Lipid Bilayer ◽  
Water Flow ◽  
Active Compound ◽  
Pore Formation ◽  
Biological Significance ◽  
Bending Rigidity ◽  
Hydrophobic Membrane ◽  
Concentration Difference ◽  
Lipid Pore ◽  
Pore Opening

The molecular details of the passive water flux across the hydrophobic membrane interior are still a matter of debate. One of the postulated mechanisms is the spontaneous, water-filled pore opening, which facilitates the hydrophilic connection between aqueous phases separated by the membrane. In the paper, we provide experimental evidence showing that the spontaneous lipid pore formation correlates with the membrane mechanics; hence, it depends on the composition of the lipid bilayer and the concentration of the osmotically active compound. Using liposomes as an experimental membrane model, osmotically induced water efflux was measured with the stopped-flow technique. Shapes of kinetic curves obtained at low osmotic pressure differences are interpreted in terms of two events: the lipid pore opening and water flow across the aqueous channel. The biological significance of the dependence of the lipid pore formation on the concentration difference of an osmotically active compound was illustrated by the demonstration that osmotically driven water flow can be accompanied by the dissipation of the pH gradient. The application of the Helfrich model to describe the probability of lipid pore opening was validated by demonstrating that the probability of pore opening correlates with the membrane bending rigidity. The correlation was determined by experimentally derived bending rigidity coefficients and probabilities of lipid pores opening.

scholarly journals LANDAU POTENTIAL STUDY OF THE CHIRAL PHASE TRANSITION IN A QCD-LIKE THEORY

2007 ◽  
Vol 16 (07n08) ◽  
pp. 2276-2281
Author(s):  
Y. TSUE ◽  
H. FUJII ◽  
Y. HASHIMOTO
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Source Term ◽  
Shape Change ◽  
Field Method ◽  
Number Density ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Potential Shape ◽  
Landau Potential

We investigate the chiral phase transition of a QCD-like theory, based the shape change of the effective potential near the critical point. The potential is constructed with the auxiliary field method, and a source term coupled to the field is introduced in order to compute the potential shape numerically. We also generalize the potential so as to have two independent order parameters, the quark scalar density and the number density. We find a tri-critical point locating at (T, μ) = (97, 203) MeV , and visualize it as the merging point of three potential minima.

Microstructure of laser-irradiated, conducting Kapton polyimide

1995 ◽  
Vol 53 ◽  
pp. 502-503
Author(s):  
D. L. Callahan ◽  
Z. Ball ◽  
H. M. Phillips ◽  
R. Sauerbrey
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Film Surface ◽  
Cross Sectional ◽  
General Utility ◽  
Transmission Electron ◽  
Considerable Debate ◽  
Potential Applications

Ultraviolet laser-irradiation can be used to induce an insulator-to-conductor phase transition on the surface of Kapton polyimide. Such structures have potential applications as resistors or conductors for VLSI applications as well as general utility electrodes. Although the percolative nature of the phase transformation has been well-established, there has been little definitive work on the mechanism or extent of transformation. In particular, there has been considerable debate about whether or not the transition is primarily photothermal in nature, as we propose, or photochemical. In this study, cross-sectional optical microscopy and transmission electron microscopy are utilized to characterize the nature of microstructural changes associated with the laser-induced pyrolysis of polyimide.Laser-modified polyimide samples initially 12 μm thick were prepared in cross-section by standard ultramicrotomy. Resulting contraction in parallel to the film surface has led to distortions in apparent magnification. The scale bars shown are calibrated for the direction normal to the film surface only.

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.

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