scholarly journals Effect of Hofmeister Anions on Interfacial Properties of Mica Surface in Concentrated Aqueous Solution

Coatings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 872
Author(s):  
Yajing Kan ◽  
Qiang Yang ◽  
Xuanxuan Zhang ◽  
Yin Zhang
Keyword(s):  
Ion Pairs ◽  
Colloid Interface ◽  
Mica Surface ◽  
Surface Forces Apparatus ◽  
Specific Effects ◽  
Low Concentrations ◽  
Hofmeister Anions ◽  
Layer Region ◽  
Hydrodynamic Effects ◽  
Charge Sign

The electric double layer (EDL) formed at the water/solid interface is the key to understanding a wide variety of natural phenomena; and nowadays, this knowledge may lead to ideas for technological innovations in the industrial and biomedical fields. The properties of the EDL on a surface directly determine the performance of an EDL-based device. In electrolyte solution, the coions with the same charge sign with the surface are usually ignored. However, they are expected to make a considerable contribution in concentrated conditions when ionic specific effects should be considered. Herein, we investigated the effect of anions in the Hofmeister series, including kosmotropes (Ac−), chaotropes (I−), and intermediate (Cl−), on the properties of the EDL on a negatively charged mica surface by observing intersurface forces using the surface forces apparatus (SFA). The SFA results indicated that at a concentration of 1 M and above, the effect of the monovalent anions in the sodium solutions were mainly correlated with their hydration behaviors. Exclusively in the solutions with strongly hydrated anions, we measured the abnormal long-range repulsions in the diffuse layer region farther away from the surface. By further investigating the solutions with kosmotropic divalent SO42− at relatively low concentrations, we may attribute the observation to the formation of ion pairs and hydrodynamic effects in the presence of concentrated kosmotropic anions. Moreover, these anions can also contribute to the formation of a complete and stable hydration layer near the surface. This work demonstrates the considerable effects of Hofmeister anionic coions on the properties of a simple colloid interface, which has attracted little attention in the past. Therefore, further investigations are desirable in the development of electrolytes and surface materials for the promising EDL-based technologies.

Gas Phase Cluster Formation of Sodium Chloride and Water: Monte Carlo Simulations

1991 ◽  
Vol 46 (4) ◽  
pp. 351-356
Author(s):  
Bernd M. Rode
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Cluster Formation ◽  
Ion Pairs ◽  
Particle Interaction ◽  
Distribution Functions ◽  
Prebiotic Atmosphere ◽  
Low Concentrations ◽  
Phase Cluster ◽  
Simulation Parameters

Abstract Monte Carlo simulations of a system of 200 water and 24 NaCl molecules at 6 different densities in the range from 0.003 g/cm3 to 0.999 g,/cm3 and T = 125 °C and 225 CC were performed to obtain some insight into cluster formation which should precede and determine the formation of aerosol structures and has possibly played some role in prebiotic atmosphere chemistry. Solute hydration occurs already at very low concentrations mainly in the form of hydrated molecules ("contact ion pairs"). At higher densities larger cluster structures are observed, leading rather continuously to the structure of the supersaturated 7.1 M NaCl solution at the same temperature. Radial distribution functions, coordination numbers and particle interaction energies are discussed with respect to the simulation parameters density and temperature

scholarly journals Retinol has specific effects on binding of thyrotrophin to cultured porcine thyrocytes

2004 ◽  
Vol 183 (3) ◽  
pp. 617-626 ◽  
Author(s):  
Eleonore Fröhlich ◽  
Anja Witke ◽  
Barbara Czarnocka ◽  
Richard Wahl
Keyword(s):  
Thyroid Cancer ◽  
Incubation Time ◽  
Time Course ◽  
Sodium Iodide ◽  
Sodium Iodide Symporter ◽  
Iodide Uptake ◽  
Specific Effects ◽  
Low Concentrations ◽  
Apoptotic Effect ◽  
Iodine 125

Retinoids are potential candidates for the treatment of thyroid cancer. However, one of the disadvantages of these substances is their dedifferentiating effect on normal non-transformed thyrocytes. To identify conditions under which no dedifferentiating effect of retinol on normal thyrocytes can be observed, we determined iodide uptake, protein iodination, expression of sodium–iodide symporter (NIS) mRNA and protein, and the binding of iodine-125-labelled bTSH in cultured porcine thyrocytes. Combination of TSH and ≤6.5 μM retinol increased iodide uptake and protein iodination compared with TSH alone over the entire incubation time, whereas TSH plus ≥13 μM retinol increased the uptake of iodine-125 only during the first 12 h but decreased it after 30 h and longer. After ≥30 h incubation times with ≥13 μM retinol, the fraction of apoptotic cells was enhanced and proliferation decreased. The incubation with retinol enhanced the binding of [125I]bTSH to thyrocytes, but did not influence expression of the NIS. With low retinol concentrations, the effect on the binding of TSH apparently predominated and retinol increased thyroid function; with higher concentrations the pro-apoptotic effect of retinol overlapped and a two-phased time course resulted. It can be concluded that low concentrations of retinol also exert differentiating effects in normal thyrocytes.

scholarly journals Adenosine 3':5'-monophosphate content and actions in the division cycle of synchronized HeLa cells.

1976 ◽  
Vol 71 (2) ◽  
pp. 515-534 ◽  
Author(s):  
C E Zeilig ◽  
R A Johnson ◽  
E W Sutherland ◽  
D L Friedman
Keyword(s):  
Cell Cycle ◽  
Cyclic Amp ◽  
Hela Cells ◽  
S Phase ◽  
Intracellular Camp ◽  
Specific Effects ◽  
Low Concentrations ◽  
High Concentrations ◽  
Camp Levels ◽  
Stimulation Of

The involvement of adenosine 3':5'-monophosphate (cAMP) in the regulation of the cell cycle was studied by determining intracellular fluctuations in cAMP levels in synchronized HeLa cells and by testing the effects of experimentally altered levels on cell cycle traverse. Cyclic AMP levels were lowest during mitosis and were highest during late G-1 or early S phase. These findings were supported by results obtained when cells were accumulated at these points with Colcemid or high levels of thymidine. Additional fluctuations in cAMP levels were observed during S phase. Two specific effects of cAMP on cell cycle traverse were found. Elevation of cAMP levels in S phase or G-2 caused arrest of cells in G-2 for as long as 10 h and lengthened M. However, once cells reached metaphase, elevation of cAMP accelerated the completion of mitosis. Stimulation of mitosis was also observed after addition of CaCl2. The specificity of the effects of cAMP was verified by demonstrating that: (a) intracellular cAMP was increased after exposure to methylisobutylxanthine (MIX) before any observed effects on cycle traverse; (b) submaximal concentrations of MIX potentiated the effects of isoproterenol; and (c) effects of MIX and isoproterenol were mimicked by 8-Br-cAMP. MIX at high concentrations inhibited G-1 traverse, but this effect did not appear to be mediated by cAMP. Isoproterenol slightly stimulated G-1 traverse and partially prevented the MIX-induced delay. Moreover, low concentrations of 8-Br-cAMP (0.10-100 muM) stimulated G-1 traverse, whereas high concentrations (1 mM) inhibited. Both of these effects were also observed with the control, Br-5'-AMP, at 10-fold lower concentrations.

scholarly journals Specific effects of calcium acetate on the self-assembly of chitosan molecules on mica surface observed with atomic force microscopy

2018 ◽  
Vol 21 (1) ◽  
pp. 2007-2015
Author(s):  
Weisha Kong ◽  
Zhiwei Wang ◽  
Shengying Fei ◽  
Qi Xiao ◽  
Mengyao Lu ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Self Assembly ◽  
Calcium Acetate ◽  
The Self ◽  
Mica Surface ◽  
Force Microscopy ◽  
Specific Effects ◽  
Atomic Force

scholarly journals Cation-Specific Effects on the Self-Assembly of Collagen Molecules Mediated by Acetate on Mica Surface Observed with Atomic Force Microscopy

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Zhiwei Wang ◽  
Qi Xiao ◽  
Xuan Song ◽  
Yunfei Wan ◽  
Jie Zhu
Keyword(s):  
Atomic Force Microscopy ◽  
Self Assembly ◽  
Ionic Concentration ◽  
Collagen Fibrils ◽  
The Self ◽  
Mica Surface ◽  
Force Microscopy ◽  
Specific Effects ◽  
Atomic Force ◽  
Base Method

The well-organized collagen layers on mica surface have drawn extensive attention for its essential applications and studies on the process of self-assembly as a model system. In this work, collagen extracted from fish scales by acid-base method was used to explore the self-assembly characters, and atomic force microscopy was applied to observe the collagen assembled on mica surface mediated by acetate with four different cations, including K+, Na+, Mg2+, and Ca2+. It showed that cations might influence the interaction between collagen fibrils and mica surface at high ionic concentration. And a similar network structure was acquired with uniform pore size for four kinds of acetates; nearly ranged collagen fibrils in the same direction were collected in Mg2+ solutions, while flat films with some fibrils were achieved in K+ solutions. The Hofmeister series and Collins’ model were adapted to explain the effects of cations and acetate on the self-assembly of collagen. These results and analysis would be helpful for directing the pattern of collagen assembly on a solid surface with a potential application in food science and engineering.

scholarly journals Subtype-Specific Effects of Lithium on Glutamate Receptor Function

1999 ◽  
Vol 81 (4) ◽  
pp. 1506-1512 ◽  
Author(s):  
Nikolas B. Karkanias ◽  
Roger L. Papke
Keyword(s):  
Glutamate Receptor ◽  
Reversal Potential ◽  
Outward Current ◽  
Evoked Responses ◽  
Receptor Function ◽  
Specific Effects ◽  
Outward Currents ◽  
Low Concentrations ◽  
Agonist Concentration ◽  
High Concentrations

Subtype-specific effects of lithium on glutamate receptor function. We report that substitution of sodium with lithium (Li+) in the extracellular solution causes subtype-specific changes in the inward and outward currents of glutamate receptors (GluRs), without a shift in reversal potential. Li+produces an increase of inward and outward currents of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors and decreases in the currents of kainate (KA) and N-methyl-d-aspartate receptors. The greatest effect of Li+ was observed with GluR3. A concentration-response curve for GluR3 reveals that the potentiation caused by Li+ is greatest at saturating agonist concentrations. GluR1, which shows no potentiation by Li+at 100 μM KA, shows a small but significant potentiation at saturating KA and glutamate concentrations. The effects of Li+ on outward current, where Li+ is not the primary charge carrier, and the lack of reversal potential shift argue for a mechanism of potentiation not associated with Li+permeation. This potentiation of current is specific for Li+ because rubidium, although causing an increase of inward current, shifted the reversal potential and did not increase outward current. The effects of Li+ are different for KA, a weak desensitizing agonist, and glutamate, a strong desensitizing agonist, suggesting that Li+ might interact with a mechanism of desensitization. By using cyclothiazide (CTZ) to reduce desensitization of GluR3, we find that for low concentrations of KA and glutamate potentiation of the response by a combination of CTZ and Li+ is no greater than by CTZ or Li+ alone. However, at high concentrations of agonist, the potentiation of the response by a combination of CTZ and Li+ is significantly greater than by CTZ or Li+ alone. This potentiation was additive for glutamate but not for KA. At high agonist concentration in the presence of CTZ, the intrinsically lower desensitization produced with KA-evoked responses may preclude Li+ from potentiating the current to the same degree as it can potentiate glutamate-evoked responses. The additive effects of CTZ and Li+ were unique to the flop variant of GluR3.

ION PAIRS IN A SOLONETZIC SOIL

1983 ◽  
Vol 63 (3) ◽  
pp. 479-484 ◽  
Author(s):  
A. ALZUBAIDI ◽  
G. R. WEBSTER
Keyword(s):  
Ion Pairs ◽  
Soil Samples ◽  
The Other ◽  
Sulfate Ion ◽  
Carbonate Ion ◽  
Low Concentrations ◽  
Solonetzic Soil ◽  
Ap Horizon ◽  
Ion Activities ◽  
High Concentrations

The kinds and concentrations of the major ion pairs were determined in saturation extracts of 141 soil samples collected from a Solonetzic soil treated with various kinds of tillage combined with surface-applied chemical amendments. The correlations between concentrations of ion pairs and EC and pH of saturation extracts were statistically tested. Sulfate ion pairs NaSO4−, MgSO40 and CaSO40 occurred in relatively high concentrations. The other ion pairs were of low concentrations. Of the total soluble Ca, ion pairs ranged from 20.8% in the Ap horizon to 50.5% in the Csk horizon and Mg was approximately the same. The comparable values for Na were 0.8% and 4.6%, respectively. Ion pairs NaSO4−, KSO4−, MgSO40 and CaSO40 were significantly correlated with EC. Only carbonate ion pairs were significantly correlated with pH. Correcting concentrations of Na, Ca and Mg for ion pairs and activities changed considerably the SAR values in the Bnt1 horizon. Key words: Ion pairs, Solonetzic soils, ion activities

Nitrate and glutamate sensing by plant roots

2005 ◽  
Vol 33 (1) ◽  
pp. 283-286 ◽  
Author(s):  
S. Filleur ◽  
P. Walch-Liu ◽  
Y. Gan ◽  
B.G. Forde
Keyword(s):  
Root Growth ◽  
Lateral Root ◽  
Lateral Roots ◽  
Primary Root ◽  
Root Tip ◽  
Root Tips ◽  
Environmental Signals ◽  
Specific Effects ◽  
Large Numbers ◽  
Low Concentrations

The architecture of a root system plays a major role in determining how efficiently a plant can capture water and nutrients from the soil. Growth occurs at the root tips and the process of exploring the soil volume depends on the behaviour of large numbers of individual root tips at different orders of branching. Each root tip is equipped with a battery of sensory mechanisms that enable it to respond to a range of environmental signals, including nutrients, water potential, light, gravity and touch. We have previously identified a MADS (MCM1, agamous, deficiens and SRF) box gene (ANR1) in Arabidopsis thaliana that is involved in modulating the rate of lateral root growth in response to changes in the external NO3− supply. Transgenic plants have been generated in which a constitutively expressed ANR1 protein can be post-translationally activated by treatment with dexamethasone (DEX). When roots of these lines are treated with DEX, lateral root growth is markedly stimulated but there is no effect on primary root growth, suggesting that one or more components of the regulatory pathway that operate in conjunction with ANR1 in lateral roots may be absent in the primary root tip. We have recently observed some very specific effects of low concentrations of glutamate on root growth, resulting in significant changes in root architecture. Experimental evidence suggests that this response involves the sensing of extracellular glutamate by root tip cells. We are currently investigating the possible role of plant ionotropic glutamate receptors in this sensory mechanism.

scholarly journals Effect of the Medium Dielectric Strength on the Activity of Alpha Chymotrypsin

1959 ◽  
Vol 43 (1) ◽  
pp. 127-137 ◽  
Author(s):  
M. Castañeda-Agulló ◽  
Luz M. del Castillo
Keyword(s):  
Dielectric Constant ◽  
Dielectric Strength ◽  
Negative Ion ◽  
Enzymatic Reactions ◽  
Specific Effects ◽  
Low Concentrations ◽  
Dielectric Effect ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Positive Ion

The rates of hydrolysis of TrEE, TEE, and ATEE1 by α-chymotrypsin were determined in media of variable dielectric strength. Many substances which modify the dielectric constant of the medium, exert additional specific effects on the reaction rate, noticeable at more or less elevated concentrations. Notwithstanding, it is possible to differentiate the dielectric and specific effects by comparing the rates in solvents of distinct nature at relatively low concentrations. Thus, the effect of varying the dielectric strength could be studied within wider ranges (ΔD = 20 with TrEE and ca. 28 with ATEE) than in the previous study of trypsin (ΔD = 12). The dielectric effect on α-chymotrypsin is the opposite of that observed with trypsin. In both cases there is a linear relationship between the logarithm of the rate of hydrolysis and the reciprocal of the dielectric constant. The slope is negative with α-chymotrypsin and positive with trypsin. According to expressions relating the dielectric constant to the rate in non-enzymatic reactions, the behavior of α-chymotrypsin is like that of a negative ion, while trypsin behaves as a positive ion. The enzyme activity appears to depend upon the arrangement of charges in the enzyme and substrate molecules, rather than on the presence of certain atomic groupings in the substrate.

scholarly journals THE INFLUENCE OF THE MEDIUM DIELECTRIC STRENGTH UPON TRYPSIN KINETICS

1959 ◽  
Vol 42 (3) ◽  
pp. 617-634 ◽  
Author(s):  
M. Castañeda-Agulló ◽  
Luz M. del Castillo
Keyword(s):  
Specific Effect ◽  
Dielectric Strength ◽  
Specific Effects ◽  
Straight Line ◽  
Low Concentrations ◽  
Other Substances ◽  
Esterolytic Activity ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Positive Ion

The use of aqueous alkali for the titration of esterolytic activity when the esters are dissolved in alcoholic solutions, results in an error due to changes in the ionization of the buffer. This is corrected by titrating with alkali in the same solvent as the substrate. Alcohols and other substances which change the dielectric strength of water modify the rate of hydrolysis of BAEE1 and TSAME by trypsin to an extent proportionate to their effect on the dielectric strength. The reaction rate increases with diminished dielectric strength and vice versa. At low concentrations of substance there seems to be no specific effect other than that derived of the variation in dielectric strength. At higher concentrations, the enzyme might be denatured. In addition, it is probable that specific effects of each substance might intervene. The Coulombic and thermic energies of activation were calculated for the two esters in various solvents. The plot of the logarithm of rate constant vs. reciprocal of dielectric constant yields a straight line with positive slope. This behavior is similar to that of a non-enzymatic positive ion-dipole reaction. Trypsin reacts like a positive ion. The possible influence of the dielectric strength on the regulation of the equilibria involved in the interconversion of the various forms of trypsin in solution (active, inactive, denatured) is discussed.

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