scholarly journals Variation of thermal conductivity of DPPC lipid bilayer membranes around the phase transition temperature

2017 ◽  
Vol 14 (130) ◽  
pp. 20170127 ◽  
Author(s):  
Sina Youssefian ◽  
Nima Rahbar ◽  
Christopher R. Lambert ◽  
Steven Van Dessel
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Phase Transition Temperature ◽  
Temperature Gradients ◽  
Phase Behaviour ◽  
Gel Phase

Given their amphiphilic nature and chemical structure, phospholipids exhibit a strong thermotropic and lyotropic phase behaviour in an aqueous environment. Around the phase transition temperature, phospholipids transform from a gel-like state to a fluid crystalline structure. In this transition, many key characteristics of the lipid bilayers such as structure and thermal properties alter. In this study, we employed atomistic simulation techniques to study the structure and underlying mechanisms of heat transfer in dipalmitoylphosphatidylcholine (DPPC) lipid bilayers around the fluid–gel phase transformation. To investigate this phenomenon, we performed non-equilibrium molecular dynamics simulations for a range of different temperature gradients. The results show that the thermal properties of the DPPC bilayer are highly dependent on the temperature gradient. Higher temperature gradients cause an increase in the thermal conductivity of the DPPC lipid bilayer. We also found that the thermal conductivity of DPPC is lowest at the transition temperature whereby one lipid leaflet is in the gel phase and the other is in the liquid crystalline phase. This is essentially related to a growth in thermal resistance between the two leaflets of lipid at the transition temperature. These results provide significant new insights into developing new thermal insulation for engineering applications.

The Effect of the Lipid Bilayer State on Fluorescence Intensity of Fluorescein-PE in a Saturated Lipid Bilayer

2000 ◽  
Vol 55 (5-6) ◽  
pp. 418-424 ◽  
Author(s):  
Marek Langner ◽  
Hanna Pruchnik ◽  
Krystian Kubica
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Lipid Bilayer ◽  
Phase Transition Temperature ◽  
Conformational Changes ◽  
Fluorescence Intensity ◽  
Electrostatic Potential ◽  
Salt Concentration ◽  
Membrane Interface

Fluorescein-PE is a fluorescence probe that is used as a membrane label or a sensor of surface associated processes. Fluorescein-PE fluorescence intensity depends not only on bulk pH, but also on the local electrostatic potential, which affects the local membrane interface proton concentration. The pH sensitivity and hydrophilic character of the fluorescein moiety was used to detect conformational changes at the lipid bilayer surface. When located in the dipalmitoylphosphatidylcholine (DPPC) bilayer, probe fluorescence depends on conformational changes that occur during phase transitions. Relative fluorescence intensity changes more at pretransition than at the main phase transition temperature, indicating that interface conformation affects the condition in the vicinity of the membrane. Local electrostatic potential depends on surface charge density, the local dielectric constant, salt concentration and water organisation. Initial increase in fluorescence intensity at temperatures preceding that of pretransition can be explained by the decreased value of the dielectric constant in the lipid polar headgroups region related in turn to decreased water organisation within the membrane interface. The abrupt decrease in fluorescence intensity at temperatures between 25 °C and 35 °C (DPPC pretransition) is likely to be caused by an increased value of the electrostatic potential, induced by an elevated value of the dielectric constant within the phosphate group region. Further increase in the fluorescence intensity at temperatures above that of the gel-liquid phase transition correlates with the calculated decreased surface electrostatic potential. Above the main phase transition temperature, fluorescence intensity increase at a salt concentration of 140 m M is larger than with 14 m M . This results from a sharp decline of the electrostatic potential induced by the phosphocholine dipole as a function of distance from the membrane surface.

scholarly journals Morphological Behavior of Lipid Bilayers Induced by Melittin near the Phase Transition Temperature

2005 ◽  
Vol 89 (5) ◽  
pp. 3214-3222 ◽  
Author(s):  
Shuichi Toraya ◽  
Takashi Nagao ◽  
Kazushi Norisada ◽  
Satoru Tuzi ◽  
Hazime Saitô ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Lipid Bilayers ◽  
Phase Transition Temperature ◽  
Morphological Behavior

scholarly journals Thermal conductivity of (VO2)1-xCux composites across the phase transition temperature

2017 ◽  
Vol 121 (15) ◽  
pp. 155103 ◽  
Author(s):  
Keshab Dahal ◽  
Qian Zhang ◽  
Ran He ◽  
Ishwar Kumar Mishra ◽  
Zhifeng Ren
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Transition Temperature ◽  
Phase Transition Temperature

scholarly journals Interaction of the sperm adhesive protein, bindin, with phospholipid vesicles. I. Specific association of bindin with gel-phase phospholipid vesicles.

1985 ◽  
Vol 100 (3) ◽  
pp. 794-799 ◽  
Author(s):  
C G Glabe
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Phospholipid Vesicles ◽  
Surface Receptors ◽  
Acrosomal Membrane ◽  
Gel Phase ◽  
Specific Association ◽  
In Vitro Interaction

Bindin is a 30,000-mol-wt protein of sea urchin sperm that is responsible for the specific adhesion of the sperm acrosomal process to the vitelline layer covering the egg plasma membrane during fertilization. Sulfated glycoconjugates are believed to be the egg surface receptors for bindin, but the mechanism by which bindin associates with the sperm acrosomal membrane is unknown. Here I report that bindin specifically associates with phospholipid vesicles in vitro. Interaction of the bindin polypeptide with liposomes was found to cause an increase in the density of the liposomes and induce the aggregation of the vesicles. A novel property of this association of bindin with membranes was that it required phospholipids in a gel phase. The interaction of bindin with liposomes was greatly reduced at temperatures above the phase transition temperature. The interaction of bindin with gel-phase vesicles appeared to be reversible, since the aggregated vesicles dissaggregated as the temperature was raised above the phase transition temperature. Association of bindin with the bilayer did not alter the accessibility of the polypeptide to cleavage by trypsin, which suggests that most of the polypeptide chain remains exposed at the surface of the membrane.

The appearance of single-ion channels in unmodified lipid bilayer membranes at the phase transition temperature

Nature ◽  
1980 ◽  
Vol 283 (5747) ◽  
pp. 585-586 ◽  
Author(s):  
V. F. Antonov ◽  
V. V. Petrov ◽  
A. A. Molnar ◽  
D. A. Predvoditelev ◽  
A. S. Ivanov
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Ion Channels ◽  
Lipid Bilayer ◽  
Phase Transition Temperature ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes

Analysis and Design of a Paraffin/Graphite Composite PCM Integrated in a Thermal Storage Unit

2008 ◽  
Author(s):  
R. Pokhrel ◽  
J. E. Gonza´lez ◽  
T. Hight ◽  
T. Adalsteinsson
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Transition Temperature ◽  
Phase Change ◽  
Specific Heat ◽  
Latent Heat ◽  
Phase Transition Temperature ◽  
Thermal Storage ◽  
High Energy ◽  
Melting And Solidification

The addition of latent heat storage systems in solar thermal applications has several benefits including volume reduction of storage tanks and maintaining the temperature range of the thermal storage. A Phase change material (PCM) provides high energy storage density at a constant temperature corresponding to its phase transition temperature. In this paper, a high temperature PCM (melting temperature 80°C) made of a composite of paraffin and graphite was tested to determine its thermal properties. Tests were conducted with a differential scanning calorimeter (DSC) and allowed the determination of the melting and solidification characteristics, latent heat, specific heat at melting and solidification, and thermal conductivity of the composite. The results of the study showed an increase in thermal conductivity by a factor of 4 when the mass fraction of the graphite in the composite was increased to 16.5%. The specific heat of the composite PCM (i.e., CPCM) decreased as the thermal conductivity increased, while the latent heat remained the same as the PCM component. In addition, the phase transition temperature was not influenced by the addition of expanded graphite. To explore the feasibility of the CPCM for practical applications, a numerical solution of the phase change transition of a small cylinder was derived. Finally, based on the properties obtained in DSC, a numerical simulation for a known volume of CPCM in a water tank was produced and indicated a reduction in solidification time by a factor of six.

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