Counter-Ion Effects and Interfacial Properties of Aqueous Tetrabutylammonium Halide Solutions

2004 ◽  
Vol 57 (12) ◽  
pp. 1211 ◽  
Author(s):  
Luboš Vrbka ◽  
Pavel Jungwirth
Keyword(s):  
Slab Geometry ◽  
Ion Interactions ◽  
Counter Ion ◽  
Counter Ions ◽  
Aqueous Solvation ◽  
Ionic Size ◽  
Surface Active ◽  
Ion Effects ◽  
Dynamics Simulations ◽  
The Individual

Aqueous solvation of tetrabutylammonium fluoride and iodide was investigated by means of molecular dynamics simulations in extended slab geometry. The varying propensities of the individual ions for the air/water interface were quantified and analyzed in terms of hydrophobic, polarization, and ion–ion interactions. While the cations behave as standard ionic surfactants, the surface behaviour of the halide counter ions strongly depends on the ionic size and polarizability—iodide is surface active, while fluoride is repelled from the interface. The counter-ion effects at different concentrations on the density and charge profiles across the aqueous slab are discussed in detail.

scholarly journals A cation counterflux supports lysosomal acidification

2010 ◽  
Vol 189 (7) ◽  
pp. 1171-1186 ◽  
Author(s):  
Benjamin E. Steinberg ◽  
Kassidy K. Huynh ◽  
Alexandre Brodovitch ◽  
Sabrina Jabs ◽  
Tobias Stauber ◽  
...  
Keyword(s):  
Ion Transport ◽  
Proton Pumping ◽  
Individual Contribution ◽  
Intact Cells ◽  
Lysosomal Ph ◽  
Anion Conductance ◽  
Counter Ion ◽  
Counter Ions ◽  
The Individual ◽  
Lysosomal Acidification

The profound luminal acidification essential for the degradative function of lysosomes requires a counter-ion flux to dissipate an opposing voltage that would prohibit proton accumulation. It has generally been assumed that a parallel anion influx is the main or only counter-ion transport that enables acidification. Indeed, defective anion conductance has been suggested as the mechanism underlying attenuated lysosome acidification in cells deficient in CFTR or ClC-7. To assess the individual contribution of counter-ions to acidification, we devised means of reversibly and separately permeabilizing the plasma and lysosomal membranes to dialyze the cytosol and lysosome lumen in intact cells, while ratiometrically monitoring lysosomal pH. Replacement of cytosolic Cl− with impermeant anions did not significantly alter proton pumping, while the presence of permeant cations in the lysosomal lumen supported acidification. Accordingly, the lysosomes were found to acidify to the same pH in both CFTR- and ClC-7–deficient cells. We conclude that cations, in addition to chloride, can support lysosomal acidification and defects in lysosomal anion conductance cannot explain the impaired microbicidal capacity of CF phagocytes.

scholarly journals Making Soup: Preparing and Validating Molecular Simulations of the Bacterial Cytoplasm

2019 ◽  
Author(s):  
Leandro Oliveira Bortot ◽  
Zahedeh Bashardanesh ◽  
David van der Spoel
Keyword(s):  
Large Scale ◽  
Biological Properties ◽  
Computational Power ◽  
E Coli ◽  
Solvent Models ◽  
Explicit Solvent ◽  
Computational Modeling And Simulation ◽  
Dynamics Simulations ◽  
The Individual ◽  
Bacterial Cytoplasm

Biomolecular crowding affects the biophysical and biochemical behavior of macro- molecules when compared to the dilute environment present in experiments made with isolated proteins. Computational modeling and simulation are useful tools to study how crowding affects the structural dynamics and biological properties of macromolecules. As computational power increased, modeling and simulating large scale all-atom explicit solvent models of the prokaryote cytoplasm become possible. In this work, we build an atomistic model of the cytoplasm of Escherichia coli composed of 1.5 million atoms and submit it to a total of 3 μs of molecular dynamics simulations. The properties of biomolecules under crowding conditions are compared to those from simulations of the individual compounds under dilute conditions. The simulation model is found to be consistent with experimental data about the diffusion coefficient and stability of macromolecules under crowded conditions. In order to stimulate further work we provide a Python script and a set of files that enables other researchers to build their own E. coli cytoplasm models to address questions related to crowding.<br>

Reversible conduction block produced by lipid-insoluble quaternary ammonium ions in cetyltrimethylammonium bromide-treated nerves

1959 ◽  
Vol 197 (3) ◽  
pp. 547-550 ◽  
Author(s):  
Raymond R. Walsh ◽  
Stanley E. Deal
Keyword(s):  
Quaternary Ammonium ◽  
Cetyltrimethylammonium Bromide ◽  
Surface Active Agent ◽  
Conduction Block ◽  
Active Agent ◽  
Ammonium Ions ◽  
Axonal Conduction ◽  
Quaternary Ammonium Ions ◽  
Surface Active ◽  
The Individual

Frog sciatic nerves were excised and treated in a Ringer's solution containing the surface-active agent, cetyltrimethylammonium bromide (CTMB). Such CTMB-treated nerves were compared to normal, untreated nerves with respect to their susceptibility to conduction block produced by six lipid-insoluble quaternary ammonium ions; the CTMB-treated nerves were rendered especially susceptible to rapid, reversible conduction block. A possible mechanism of CTMB action is proposed, involving chemo-dissection of permeability barriers which normally surround the individual axons. The findings that acetylcholine, curare, etc. can produce reversible, axonal conduction block in CTMB-treated nerves are not inconsistent with a theory of cholinergic impulse conduction.

scholarly journals Counter ion effects on the energy transfer processes in PPV

2014 ◽  
Vol 605-606 ◽  
pp. 147-151 ◽  
Author(s):  
Paulo Alliprandini Filho ◽  
Alexandre Marletta ◽  
Leni Akcelrud ◽  
Osvaldo N. Oliveira
Keyword(s):  
Energy Transfer ◽  
Transfer Processes ◽  
Counter Ion ◽  
Ion Effects

ChemInform Abstract: Thermal Fragmentation of 2-Chloropentylphosphonic Salts in the Solid State. Counter-Ion Effects on Reactivity and Selectivity.

ChemInform ◽  
2010 ◽  
Vol 29 (2) ◽  
pp. no-no
Author(s):  
B. G. MAFUNDA ◽  
A. M. MODRO ◽  
T. A. MODRO ◽  
E. STRAUSS ◽  
C. A. STRYDOM
Keyword(s):  
Solid State ◽  
Thermal Fragmentation ◽  
Counter Ion ◽  
Ion Effects

scholarly journals Noise spectra of K+ and NH4+ ions at over-limiting current in an electrochemical system with a cation exchange membrane

2013 ◽  
Vol 3 (3) ◽  
pp. 291-296
Author(s):  
K. Oulmi ◽  
K. E. Bouhidel ◽  
G. M. Andreadis
Keyword(s):  
Limiting Current ◽  
Electrical Noise ◽  
Singular Behaviour ◽  
Counter Ion ◽  
Power Spectral ◽  
Counter Ions ◽  
Voltage Curve ◽  
Current Voltage ◽  
Current Voltage Curve ◽  
Exchange Membrane

The present work investigates the effect of the counter ion nature on the noise of the over-limiting current (Iov). Moreover, the electrochemical methods, current voltage curve (I–V) and the chronopotentiometry (V–t) measurements are applied. The over-limiting current is always accompanied by a neat electrical noise. It is a well accepted experimental phenomenon. The study of this noise may contribute to a better understanding of the Iov and the feasibility of electrodialysis operation at this current in terms of energy consumption. The electrical noise depends directly on the counter ion nature. The power spectral density of the membrane's potential fluctuation was obtained via Fourier analysis of the time series recorded during the transport of counter ions (K+ and NH4+). The spectra are evaluated above the limiting current indicating the differences between the K+ and the NH4+. It is found that the cation NH4+ presents a singular behaviour and the noise is minimal.

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