scholarly journals Effects of nicotine on the thermodynamics of the DPPC phase coexistence region

2019 ◽  
Author(s):  
Ernanni D. Vieira ◽  
A. J. Costa-Filho ◽  
Luis. G. M. Basso
Keyword(s):  
Heat Capacity ◽  
Electrostatic Interactions ◽  
Lipid Membrane ◽  
Phase Coexistence ◽  
Thermodynamic Quantities ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Membrane Function ◽  
Non Linear ◽  
Entropically Driven

ABSTRACTPhase separation plays critical roles in several membrane functions, and reduction or disappearance of phase coexistence by action of membrane-interacting molecules have been implicated in membrane function impairment. Here, we applied differential scanning calorimetry, electron paramagnetic resonance (EPR), and non-linear least-squares (NLLS) spectral simulations to study the effects of nicotine, a parasympathomimetic drug, on the two-phase coexistence of dipalmitoyl phosphatidylcholine (DPPC) lipid membrane. The thermodynamic quantities describing the DPPC phase coexistence are temperature dependent, giving rise to non-linear van’t Hoff behavior. Our results showed that nicotine preferentially binds to the fluid phase and modifies the enthalpy and entropy changes of the DPPC heat capacity profile, while marginally perturbing the homogeneous gel and fluid phases. An EPR/NLLS/van’t Hoff analysis of the DPPC phase coexistence revealed that nicotine significantly modified the temperature dependence of the free energy change of the two-phase equilibrium from a cubic to a parabolic behavior, resulting in an alteration of the thermodynamical driving force and the balance of the non-covalent interactions of the lipids in equilibrium. The thermotropic behavior of the enthalpy, entropy, and heat capacity changes, as determined by EPR, indicated that nicotine modified the relative contributions of hydrogen-bonding, electrostatic interactions, and conformational entropy of the lipids to the thermodynamics of the phase coexistence. The predominantly entropically-driven gel-fluid transition in nicotine-free DPPC changes to a temperature-triggered entropically-driven or enthalpically-driven process in nicotine-bound DPPC. Further applications of this thermodynamic EPR/NLLS/van’t Hoff analysis are discussed.

Raman Spectroscopic Study of Phase Coexistence in Binary Phospholipid Bilayers

2020 ◽  
Vol 75 (1) ◽  
pp. 87-93 ◽  
Author(s):  
Sergey V. Adichtchev ◽  
Konstantin A. Okotrub ◽  
Alexey M. Pugachev ◽  
Irina V. Zaytseva ◽  
Nikolay V. Surovtsev
Keyword(s):  
Raman Line ◽  
Low Frequency ◽  
Phospholipid Bilayers ◽  
Phase Coexistence ◽  
Lipid Phase ◽  
Label Free ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Raman Spectroscopic ◽  
Raman Scattering Spectra

Binary phospholipid bilayers composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-palmitoyl-sn-glycero-3-phosphocholine (DPPC) were studied by Raman spectroscopy and differential scanning calorimetry (DSC). We examined features in Raman scattering spectra that are sensitive to the lipid phase and, therefore, could indicate the phase coexistence. It was found that the low-frequency half-width of half-maximum (LHWHM) of the 2850 cm−1 Raman line, corresponding to the symmetric CH2 stretching vibrations, unequivocally reveals the coexisting phospholipids in ordered and disordered conformational states, which correspond to ordered and disordered phases coexistence, in the DPPC mole concentration range from 0.4 to 0.9. The phase coexistence in this concentration range was supported by the particular concentration behavior of the ratio between the intensities of the 2880 cm−1 antisymmetric CH2 vibration line and the 2850 cm−1 symmetric one. It was also shown that the spectral shape of the 1300 cm−1 Raman line, corresponding to the CH2 twisting vibrations, is a good indicator for the phase state and phase coexistence in the phospholipid bilayers. Comparison with the DSC curves confirmed that in the DPPC mole concentration range from 0.4 to 0.9, the two phase transition peaks are observed in DSC curve, those positions are independent of the DPPC concentration. The outcome of the study is the robust label-free contactless approach for the detection of the lipid phase separation, which can be realized with the micrometer resolution.

scholarly journals Синтез, структура и теплофизические свойства оксидов системы YVO_4-BiVO-=SUB=-4-=/SUB=-

2020 ◽  
Vol 62 (4) ◽  
pp. 640
Author(s):  
Л.Т. Денисова ◽  
Е.О. Голубева ◽  
Л.Г. Чумилина ◽  
В.М. Денисов
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
High Temperature ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Phase Synthesis ◽  
High Temperature Heat Capacity ◽  
Temperature Heat

Abstract The Y_0.4Bi_0.6VO_4 and Y_0.6Bi_0.4VO_4 solid solutions two-phase at x _Bi = 0.95, 0.90, and 0.80 have been formed by the solid-phase synthesis from the initial Y_2O_3, Bi_2O_3, and V_2O_5 oxides burned in air at a temperature of 1173 K for 200 h and their high-temperature heat capacity has been measured in the range of 350–1000 K by differential scanning calorimetry. The thermodynamic properties of the solution solutions have been calculated using the data obtained.

scholarly journals Equal Area Laws and Latent Heat ford-Dimensional RN-AdS Black Hole

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Li-Chun Zhang ◽  
Hui-Hua Zhao ◽  
Ren Zhao ◽  
Meng-Sen Ma
Keyword(s):  
Black Hole ◽  
Phase Diagrams ◽  
Latent Heat ◽  
Critical Value ◽  
Phase Coexistence ◽  
Thermodynamic Quantities ◽  
Two Phase ◽  
Equal Area ◽  
The Real ◽  
Coexistence Line

We study the equal area laws ofd-dimensional RN-AdS black hole. We choose two kinds of phase diagrams,P-VandT-S. We employ the equal area laws to find an isobar which is the real two-phase coexistence line. Our calculation is much simpler to derive the critical value of the thermodynamic quantities. According to the thermodynamic quantities, we also study the latent heat of the black hole.

THE MECHANISM OF RAISING AND QUANTIFICATION OF SPECIFIC HEAT FLUX AT BOILING OF NANOFLUIDS IN FREE CONVECTION CONDITIONS

2017 ◽  
pp. 25-34
Author(s):  
V.N. Moraru
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Capacity ◽  
Specific Heat ◽  
Chemical Properties ◽  
Heating Surface ◽  
Physical Models ◽  
Superheated Liquid ◽  
Two Phase ◽  
Boiling Process

The results of our work and a number of foreign studies indicate that the sharp increase in the heat transfer parameters (specific heat flux q and heat transfer coefficient _) at the boiling of nanofluids as compared to the base liquid (water) is due not only and not so much to the increase of the thermal conductivity of the nanofluids, but an intensification of the boiling process caused by a change in the state of the heating surface, its topological and chemical properties (porosity, roughness, wettability). The latter leads to a change in the internal characteristics of the boiling process and the average temperature of the superheated liquid layer. This circumstance makes it possible, on the basis of physical models of the liquids boiling and taking into account the parameters of the surface state (temperature, pressure) and properties of the coolant (the density and heat capacity of the liquid, the specific heat of vaporization and the heat capacity of the vapor), and also the internal characteristics of the boiling of liquids, to calculate the value of specific heat flux q. In this paper, the difference in the mechanisms of heat transfer during the boiling of single-phase (water) and two-phase nanofluids has been studied and a quantitative estimate of the q values for the boiling of the nanofluid is carried out based on the internal characteristics of the boiling process. The satisfactory agreement of the calculated values with the experimental data is a confirmation that the key factor in the growth of the heat transfer intensity at the boiling of nanofluids is indeed a change in the nature and microrelief of the heating surface. Bibl. 20, Fig. 9, Tab. 2.

scholarly journals Basic Residue Clusters in Intrinsically Disordered Regions of Peripheral Membrane Proteins: Modulating 2D Diffusion on Cell Membranes

Physchem ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 152-162
Author(s):  
Miquel Pons
Keyword(s):  
Membrane Proteins ◽  
Electrostatic Interactions ◽  
Lipid Membrane ◽  
Conformational Ensemble ◽  
Basic Residue ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Regions ◽  
Peripheral Membrane Proteins ◽  
Charged Residues ◽  
Disordered Regions

A large number of peripheral membrane proteins transiently interact with lipids through a combination of weak interactions. Among them, electrostatic interactions of clusters of positively charged amino acid residues with negatively charged lipids play an important role. Clusters of charged residues are often found in intrinsically disordered protein regions, which are highly abundant in the vicinity of the membrane forming what has been called the disordered boundary of the cell. Beyond contributing to the stability of the lipid-bound state, the pattern of charged residues may encode specific interactions or properties that form the basis of cell signaling. The element of this code may include, among others, the recognition, clustering, and selective release of phosphatidyl inositides, lipid-mediated protein-protein interactions changing the residence time of the peripheral membrane proteins or driving their approximation to integral membrane proteins. Boundary effects include reduction of dimensionality, protein reorientation, biassing of the conformational ensemble of disordered regions or enhanced 2D diffusion in the peri-membrane region enabled by the fuzzy character of the electrostatic interactions with an extended lipid membrane.

GDC - Y 2 O 3 Oxide Based Two Phase Nanocomposite Electrolyte

2011 ◽  
Vol 8 (4) ◽  
Author(s):  
Rizwan Raza ◽  
Ghazanfar Abbas ◽  
S. Khalid Imran ◽  
Imran Patel ◽  
Bin Zhu
Keyword(s):  
Fuel Cell ◽  
Ionic Conductivities ◽  
Morphological Properties ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Composite Electrolyte ◽  
Significant Performance ◽  
Advanced Fuel ◽  
Nanocomposite Electrolyte ◽  
Scherrer Formula

Oxide based two phase composite electrolyte (Ce0.9Gd0.1O2–Y2O3) was synthesized by coprecipitation method. The nanocomposite electrolyte showed the significant performance of power density 785 mW cm−2 and higher conductivities at relatively low temperature 550°C. Ionic conductivities were measured with ac impedance spectroscopy and four-probe dc method. The structural and morphological properties of the prepared electrolyte were investigated by scanning electron microscope (SEM). The thermal stability was determined with differential scanning calorimetry. The particle size that was calculated with Scherrer formula, 15–20 nm, is in a good agreement with the SEM and X- ray diffraction results. The purpose of this study is to introduce the functional nanocomposite materials for advanced fuel cell technology to meet the challenges of solid oxide fuel cell.

FROUDE’S LAW OF SIMILITUDE – CONTEMPORARY AND FUTURE SEAKEEPING TESTING

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
R P Dallinga ◽  
R H M Huijsmans
Keyword(s):  
Model Test ◽  
Scale Effects ◽  
Higher Order ◽  
Air Pressure ◽  
Test Results ◽  
Viscous Effects ◽  
Two Phase ◽  
Scale Models ◽  
Non Linear

Historically “scale effects” in the interpretation of tests with scale models in waves using Froude’s Law of Similitude are mostly associated with viscous effects. Nowadays, with a much more complete modelling of reality and a focus on higher order non-linear phenomena, scaling of model test results implies a wider range of assumptions than the validity of Froude’s Law. Our contribution to the conference is a visionary review of contemporary and future problems in the interpretation of these tests. In this context we will discuss the developments in test techniques, including the development of a new Two-Phase Laboratory facilitating seakeeping and sloshing tests at reduced air pressure.

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