scholarly journals Charge regulating macro-ions in salt solutions: screening properties and electrostatic interactions

Soft Matter ◽  
2018 ◽  
Vol 14 (29) ◽  
pp. 6058-6069 ◽  
Author(s):  
Yael Avni ◽  
Tomer Markovich ◽  
Rudolf Podgornik ◽  
David Andelman
Keyword(s):  
Salt Solution ◽  
Electrostatic Interactions ◽  
Regulation Mechanism ◽  
Salt Solutions ◽  
Charge Regulation

We revisit the charge-regulation mechanism of macro-ions and apply it to mobile macro-ions in a bathing salt solution.

scholarly journals Ion-specific thermodynamical properties of aqueous proteins

2010 ◽  
Vol 82 (1) ◽  
pp. 109-126 ◽  
Author(s):  
Eduardo R.A. Lima ◽  
Evaristo C. Biscaia Jr. ◽  
Mathias Boström ◽  
Frederico W. Tavares
Keyword(s):  
Electrostatic Interactions ◽  
Colloidal Particles ◽  
Effective Interaction ◽  
Virial Coefficients ◽  
Water Structure ◽  
Hydrophobic Surface ◽  
Colloidal Systems ◽  
Salt Solutions ◽  
Monovalent Ions ◽  
Pharmaceutical Industries

Ion-specific interactions between two colloidal particles are calculated using a modified Poisson-Boltzmann (PB)equationandMonteCarlo(MC)simulations. PBequationspresentgoodresultsofionicconcentration profiles around a macroion, especially for salt solutions containing monovalent ions. These equations include not only electrostatic interactions, but also dispersion potentials originated from polarizabilities of ions and proteins. This enables us to predict ion-specific properties of colloidal systems. We compared results obtained from the modified PB equation with those from MC simulations and integral equations. Phase diagrams and osmotic second virial coefficients are also presented for different salt solutions at different pH and ionic strengths, in agreement with the experimental results observed Hofmeister effects. In order to include the water structure and hydration effect, we have used an effective interaction obtained from molecular dynamics of each ion and a hydrophobic surface combined with PB equation. The method has been proved to be efficient and suitable for describing phenomena where the water structure close to the interface plays an essential role. Important thermodynamic properties related to protein aggregation, essential in biotechnology and pharmaceutical industries, can be obtained from the method shown here.

Protein Adsorption at Charged Surfaces: The Role of Electrostatic Interactions and Interfacial Charge Regulation

Langmuir ◽  
2011 ◽  
Vol 27 (6) ◽  
pp. 2634-2643 ◽  
Author(s):  
Rune A. Hartvig ◽  
Marco van de Weert ◽  
Jesper Østergaard ◽  
Lene Jorgensen ◽  
Henrik Jensen
Keyword(s):  
Protein Adsorption ◽  
Electrostatic Interactions ◽  
Charge Regulation ◽  
Charged Surfaces ◽  
Interfacial Charge

Colloidal electrostatic interactions between TiO2 particles modified by thin salt solution layers

Soft Matter ◽  
2010 ◽  
Vol 6 (19) ◽  
pp. 4800 ◽  
Author(s):  
Peng Tan ◽  
Jiping Huang ◽  
Dakang Liu ◽  
Wenjia Tian ◽  
Luwei Zhou
Keyword(s):  
Salt Solution ◽  
Electrostatic Interactions ◽  
Tio2 Particles

Investigations Into the Mobilization of Actinides From ILW Conditioned in Cement and Bitumen and Studies of their Sorptive and Migration Behaviour in Both the Near- and Far-Fields for a Repository Contained in a Deep Salt Environment

1985 ◽  
Vol 50 ◽  
Author(s):  
A. R. Flambard ◽  
H.-U. Fusban ◽  
Ch. Keiling ◽  
G. Marx
Keyword(s):  
Salt Solution ◽  
Ph Effect ◽  
Salt Dome ◽  
The Other ◽  
Competitive Sorption ◽  
Salt Solutions ◽  
Northern Germany ◽  
Mobility Studies ◽  
Simulated Waste ◽  
And Migration

AbstractExperiments have been carried out into the leaching of ILW conditioned in cement and bitumen in concentrated salt solutions. Although difficult to observe with real waste leachates, investigations into the leaching of a simulated waste in cement have indicated leached transuranic levels of ca. 10−9 M ; the amount of activity leached by a quinary salt solution being 102 - 103 times higher . This has been interpreted in terms of a pH effect. For the real waste, spectroscopy has indicated a significantly larger release of Cs from cement than from bitumen. For all waste samples a notable absence of colloidal material was observed ; an observation which can be explained in terms of the high solution ionic strengths and the corresponding influence upon radionuclide solvation.Transuranic mobility studies through salt and sand from a salt dome in Northern Germany have shown the presence of at least two types of species of wildly differing mobility ; one migrating with approximately the same velocity as that of the solvent front and the other strongly retarded. Actinide recoveries (i.e. that passing through the columns) could be strongly influenced by either changing the system pH or by the addition of a competitor such as Ce ; the latter effect pointing to a competitive sorption.

scholarly journals THE SWELLING AND OSMOTIC PRESSURE OF GELATIN IN SALT SOLUTIONS

1926 ◽  
Vol 8 (4) ◽  
pp. 317-337 ◽  
Author(s):  
John H. Northrop ◽  
M. Kunitz
Keyword(s):  
Bulk Modulus ◽  
Osmotic Pressure ◽  
Salt Solution ◽  
Modulus Of Elasticity ◽  
Elastic Limit ◽  
Ion Concentration ◽  
Salt Solutions ◽  
Original Volume ◽  
Expected Result ◽  
Do So

1. The swelling and the osmotic pressure of gelatin at pH 4.7 have been measured in the presence of a number of salts. 2. The effect of the salts on the swelling is closely paralleled by the effect on the osmotic pressure, and the bulk modulus of the gelatin particles calculated from these figures is constant up to an increase in volume of about 800 per cent. As soon as any of the salts increase the swelling beyond this point, the bulk. modulus decreases. This is interpreted as showing that the elastic limit has been exceeded. 3. Gelatin swollen in acid returns to its original volume after removal of the acid, while gelatin swollen in salt solution does not do so. This is the expected result if, as stated above, the elastic limit had been exceeded in the salt solution. 4. The modulus of elasticity of gelatin swollen in salt solutions varies in the same way as the bulk modulus calculated from the osmotic pressure and the swelling. 5. The increase in osmotic pressure caused by the salt is reversible on removal of the salt. 6. The observed osmotic pressure is much greater than the osmotic pressure calculated from the Donnan equilibrium except in the case of AlCl3, where the calculated and observed pressures agree quite closely. 7. The increase in swelling in salt solutions is due to an increase in osmotic pressure. This increase is probably due to a change in the osmotic pressure of the gelatin itself rather than to a difference in ion concentration.

scholarly journals Production of Magnesium Oxides from Raw Salt Solution Using Electrochemical Precipitation Method as a Heterogeneous Catalyst for Transesterification of Coconut Oil

2020 ◽  
Vol 71 (8) ◽  
pp. 148-158
Author(s):  
Kamisah D. Pandiangan ◽  
Wasinton Simanjuntak ◽  
R. Supriyanto ◽  
Ilim Ilim ◽  
Ponco Prasetyo ◽  
...  
Keyword(s):  
Salt Concentration ◽  
Salt Solution ◽  
Coconut Oil ◽  
Precipitation Method ◽  
Electrolysis Time ◽  
Salt Solutions ◽  
X Ray ◽  
Electrochemical Conversion ◽  
Concentration Potential ◽  
Main Component

This study was conducted to explore the production of magnesium oxide from raw salt solution using electrochemical precipitation, followed by calcination. Electrochemical precipitation was conducted by electrolysis of the salt solution using nickel rods as cathodes and graphite as anodes. Two sets of salt solutions were prepared: one set without pretreatment and another with BaCl2 pretreatment. The solutions were used to study the effect of salt concentration, potential, and electrolysis time. The representatives of the MgO produced were tested as catalysts for transesterification of coconut oil. The results indicate that optimum mass of precipitate was produced from 400 mg/L salt solution electrolyzed using 8 V for 60 min. Elemental analysis using X-Ray Fluorescence (XRF) revealed the presence of Mg as the main component of the precipitate, confirming the electrochemical conversion of Mg2+ into solid Mg(OH)2. The MgO with the purity of 74.23% and 88.87% was produced from non-pretreated and pretreated salt solution, respectively. The transesterification experiments indicate that the yield of 90% and 98% was achieved using the MgO produced from non-pretreated and pretreated salt solution, respectively.

scholarly journals Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes

2019 ◽  
Author(s):  
Pablo M. Blanco ◽  
Sergio Madurga ◽  
Claudio F. Narambuena ◽  
Francesc Mas ◽  
Josep L. Garcés
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Persistence Length ◽  
Excluded Volume ◽  
Average Charge ◽  
Zero Force ◽  
Charge Regulation ◽  
Ph Values

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte i.e. proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included in the model. It can be regarded as a kind of "minimal'' model in the sense that contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase, and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 to low pH-values (Pincus regime), is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

scholarly journals Quantitative Prediction of Charge Regulation in Oligopeptides

2020 ◽  
Author(s):  
Raju Lunkad ◽  
Anastasiia Murmiliuk ◽  
Pascal Hebbeker ◽  
Milan Boublík ◽  
Zdeněk Tošner ◽  
...  
Keyword(s):  
Electrostatic Interactions ◽  
Weak Acid ◽  
Coarse Grained ◽  
Disordered Proteins ◽  
Quantitative Prediction ◽  
Bottom Up ◽  
Charge Regulation ◽  
Flexible Polymer ◽  
Acid And Base ◽  
Base Side

Weak ampholytes are ubiquitous in nature and commonly found in artificial pH-responsive systems. However, our limited understanding of their charge regulation and the lack of predictive capabilities hinder the bottom-up design of such systems. Here, we used a coarse-grained model of a flexible polymer with weakly ionisable monomer units to quantitatively analyse the ionisation behaviour of two oligopeptides. Our model predicts differences in the charge states between oligopeptides and monomeric amino acids, showing that conformational flexibility and electrostatic interactions between weak acid and base side chains play a key role in the charge regulation. By comparing our simulations with experimental results from potentiometric titration, capillary zone electrophoresis and NMR, we demonstrated that our model reliably predicts the charge state of various peptide sequences. Ultimately, our model is the first step towards understanding the charge regualtion in flexible disordered proteins, and towards using predictive bottom-up design of responsive ampholytes to tailor their<br>properties as a function of charge and pH.<br>

Sign in / Sign up

Export Citation Format

Share Document