scholarly journals A Model Representing a Physiological Role of CO2 at the Cell Membrane

1961 ◽  
Vol 44 (5) ◽  
pp. 869-887 ◽  
Author(s):  
D. F. Sears ◽  
R. M. Eisenberg
Keyword(s):  
Cell Membrane ◽  
Interfacial Tension ◽  
Sessile Drop ◽  
Pure Water ◽  
Physiological Role ◽  
Electrolyte Solutions ◽  
Chloride Solutions ◽  
Interfacial Tensions ◽  
Molecular Arrangement

A model is presented suggesting the interaction of CO2 and bicarbonate on lipids of the cell membrane. The interfacial tensions between water and oil (benzene) phases were measured using the stalagmometer and the sessile drop methods. Effects of electrolyte solutions and of CO2 on molecular arrangement at the interface were calculated. Chloride solutions against oleic acid in benzene produced little decrease in interfacial tension from that measured for pure water against the oil phase. Presence or absence of CO2 caused no change in interfacial tension of water or chloride solutions against the oil phase. Bicarbonate salts in the absence of CO2 caused marked decreases in interfacial tension from that measured for water or chloride solutions. Concomitant with this decrease in interfacial tension were an increase in hydration of the interface and changes in molecular spacings of the lipid. This hydration may be considered as reflecting a more ionic-permeable cell membrane. The addition of CO2 to the bicarbonates caused an increase in interfacial tension of the model, approaching that of the chlorides, with decreased hydration of the interface. Viewed as occurring at the cell membrane this would make the lipid more continuous and decrease the ease of ionic penetration. In this way the action of bicarbonates and CO2 at the interface suggests an explanation of the action of CO2 on the cell.

scholarly journals Surface and interfacial tensions of aqueous dispersions of charged colloidal (clay) particles

1994 ◽  
Vol 72 (9) ◽  
pp. 1915-1920 ◽  
Author(s):  
Laurier L. Schramm ◽  
Loren G. Hepler
Keyword(s):  
Interfacial Tension ◽  
Pure Water ◽  
Surface Tensions ◽  
Flow Rates ◽  
Aqueous Dispersions ◽  
Clay Particles ◽  
Interfacial Tensions ◽  
Aqueous Suspensions ◽  
Colloidal Clay ◽  
Effect Of Surface

We have measured (du Nouy ring and maximum bubble pressure methods) suspension–air surface tensions of aqueous suspensions of montmorillonite and have observed that these surface tensions are larger than those of pure water at the same temperatures. Further measurements have shown that dispersed montmorillonite also increases the suspension–toluene interfacial tension compared with that of pure water–toluene. Similar measurements on aqueous suspensions of kaolinite have yielded suspension–air interfacial tensions with uncertainties as large as the observed (small) effect, and also shown that the suspension–toluene interfacial tension is decreased (opposite to the effect of montmorillonite) by amounts larger than the experimental uncertainties. Measurements of maximum bubble pressures at different flow rates have provided information about the effect of surface age on observed surface tensions.

scholarly journals Bidirectional transport of glutamine across the cell membrane in rat liver

1983 ◽  
Vol 216 (2) ◽  
pp. 401-408 ◽  
Author(s):  
P Fafournoux ◽  
C Demigné ◽  
C Rémésy ◽  
A Le Cam
Keyword(s):  
Cell Membrane ◽  
Physiological Role ◽  
Minor Role ◽  
Facilitated Diffusion ◽  
Dependent Component ◽  
Glutamine Transport ◽  
Diffusion Component ◽  
Bidirectional Transport ◽  
A Minor

Hepatocytes isolated from fed rats were used to investigate glutamine transport. Glutamine transport appears as a composite process involving at least two saturable components. The Na+-dependent component probably represents the entry through the N system. The Na+-independent component was also inhibited by histidine and exhibited trans-stimulation, suggestive of a facilitated diffusion process. Kinetic parameters for both systems suggest that facilitated diffusion only plays a minor role in glutamine influx. In contrast, the Km for glutamine efflux was consistent with a physiological role of the facilitated-diffusion component in glutamine release. In Na+ medium, relatively constant distribution ratios (about 8) between intra- and extra-cellular concentrations were observed, with external glutamine ranging from 0.5 to 5 mM. The present observations suggest that glutamine influx might largely be mediated by the N system, whereas facilitated diffusion allows hepatocytes to release glutamine when intracellular concentrations are elevated. The physiological consequences of this bidirectional transfer of glutamine across the liver cell membrane is discussed.

Study on Interface Behaviour of the Weak Alkali Ternary System

2012 ◽  
Vol 524-527 ◽  
pp. 1905-1909
Author(s):  
Wen Xiang Wu ◽  
Li Min Wang ◽  
Dong Zhang
Keyword(s):  
Ternary System ◽  
Interfacial Tension ◽  
Polymer Concentration ◽  
Interfacial Tensions ◽  
Order Of Magnitude ◽  
Low Interfacial Tension ◽  
Concentration Changes ◽  
Reduction Effect ◽  
Sacrificial Agent

Interfacial tensions between the weak alkali ternary system with surfactant SHSA-HN6 and Henan crude oil were measured. The effects of adding Na2CO3 and Na2CO3 concentration, SHSA-HN6 and polymer concentration on interfacial tensions were examined. The results showed that the interfacial tension reduction effect of the weak alkali ternary system was better than that of the alkali-free binary system, and the ultra-low interfacial tension （10-3 mN/m order of magnitude）for weak alkali ternary system could be reached more rapidly; the influence of polymer concentration changes on static interfacial tension of the weak alkali ternary system was small and the higher the polymer concentration was，the longer the time to reach ultra-low interfacial tension was; the interfacial tension can still be ultra-low when concentration of every component was reduced simultaneously in the weak alkali ternary system; adding Na2CO3 not only can reduce the interfacial tension and but also plays a role of sacrificial agent.

scholarly journals Measuring the Anisotropy in Interfacial Tension of Nematic Liquid Crystals

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 687
Author(s):  
Lawrence W. Honaker ◽  
Anjali Sharma ◽  
Andy Schanen ◽  
Jan P. F. Lagerwall
Keyword(s):  
Interfacial Tension ◽  
Molar Mass ◽  
Pure Water ◽  
Sodium Dodecylsulfate ◽  
Poly Vinyl Alcohol ◽  
Empirical Knowledge ◽  
Interfacial Tensions ◽  
Stabilizer Concentration ◽  
Aspiration Technique ◽  
The Common

Liquid crystal (LC) phases typically show anisotropic alignment-dependent properties, such as viscosity and dielectric permittivity, so it stands to reason that LCs also have anisotropic interfacial tensions. Measuring the interfacial tension γ of an LC with conventional methods, such as pendant drops, can be challenging, however, especially when we need to know γ for different LC aligning conditions, as is the case when we seek Δγ, the interfacial tension anisotropy. Here, we present measurements of Δγ of the common synthetic nematic LC compound 5CB against water using a microfluidic droplet aspiration technique. To ensure tangential and normal alignment, respectively, we add poly(vinyl alcohol) (PVA) and sodium dodecylsulfate (SDS), respectively, as a stabilizer and measure γ for different concentrations of stabilizer. By fitting the Szyszkowski equation to the data, we can extrapolate to zero-stabilizer concentration, obtaining the γ of 5CB to pure water for each alignment. For normal alignment, we find γ⊥=31.9±0.8 mN·m−1, on the order of 1 mN·m−1 greater than γ||=30.8±5 mN·m−1 for tangential alignment. This resonates with the empirical knowledge that 5CB aligns tangentially to an interface with pure water. The main uncertainty arises from the use of polymeric PVA as tangential-promoting stabilizer. Future improvements in accuracy may be expected if PVA can be replaced by a low molar mass stabilizer that ensures tangential alignment.

Physiological Role of Cyclic Electron Flow in Higher Plants

2012 ◽  
Vol 30 (1) ◽  
pp. 100
Author(s):  
Wei HUANG ◽  
Shi-Bao ZHANG ◽  
Kun-Fang CAO
Keyword(s):  
Higher Plants ◽  
Electron Flow ◽  
Physiological Role ◽  
Cyclic Electron Flow

The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

1999 ◽  
Vol 39 (7) ◽  
pp. 91-98 ◽  
Author(s):  
Ryan N. Jordan ◽  
Eric P. Nichols ◽  
Alfred B. Cunningham
Keyword(s):  
Mass Transfer ◽  
Cell Membrane ◽  
Substrate Concentration ◽  
Water Interface ◽  
Industrial Systems ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

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