Articoli di riviste: "Ionic strength"

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Kreusser, Jannette, Fabian Jirasek e Hans Hasse. "Influence of Salts on the Adsorption of Lysozyme on a Mixed-Mode Resin". Adsorption Science & Technology 2021 (23 gennaio 2021): 1–11. http://dx.doi.org/10.1155/2021/6681348.

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Mixed-mode chromatography (MMC), which combines features of ion exchange chromatography (IEC) and hydrophobic interaction chromatography (HIC), is an interesting method for protein separation and purification. The design of MMC processes is challenging as adsorption equilibria are influenced by many parameters, including ionic strength and the presence of different salts in solution. Systematic studies on the influence of those parameters in MMC are rare. Therefore, in the present work, the influence of four salts, namely, sodium chloride, sodium sulfate, ammonium chloride, and ammonium sulfate, on the adsorption of lysozyme on the mixed-mode resin Toyopearl MX-Trp-650M at pH 7.0 and 25°C was studied systematically in equilibrium adsorption experiments for ionic strengths between 0 mM and 3000 mM. For all salts, a noticeable adsorption strength was observed over the entire range of studied ionic strengths. An exponential decay of the loading of the resin with increasing ionic strength was found until approx. 1000 mM. For higher ionic strengths, the loading was found to be practically independent of the ionic strength. At constant ionic strength, the highest lysozyme loadings were observed for ammonium sulfate, the lowest for sodium chloride. A mathematical model was developed that correctly describes the influence of the ionic strength as well as the influence of the studied salts. The model is the first that enables the prediction of adsorption isotherms of proteins on mixed-mode resins in a wide range of technically interesting conditions, accounting for the influence of the ionic strength and four salts of practical relevance.

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Pham, T. V., e K. C. Westaway. "Solvent effects on nucleophilic substitution reactions. III. The effect of adding an inert salt on the structure of the SN2 transition state". Canadian Journal of Chemistry 74, n. 12 (1 dicembre 1996): 2528–30. http://dx.doi.org/10.1139/v96-283.

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The nitrogen and secondary α-hydrogen–deuterium kinetic isotope effects found for the SN2 reaction between thiophenoxide ion and benzyldimethylphenylammonium ion at different ionic strengths in DMF at 0 °C indicate that the structure of the transition state changes markedly with the ionic strength of the reaction mixture. In fact, a more reactant-like, more ionic, transition state is found at the higher ionic strength. This presumably occurs because a more ionic transition state is more stable in the more ionic solvent. Key words: transition state, ionic strength, secondary α deuterium kinetic isotope effects, nitrogen isotope effects, SN2.

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Dolling, PJ, e GSP Ritchie. "Estimates of soil solution ionic strength and the determination of pH in West Australian soils". Soil Research 23, n. 2 (1985): 309. http://dx.doi.org/10.1071/sr9850309.

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The average ionic strength of 20 West Australian soils was found to be 0.0048. The effects of three electrolytes (deionized water, CaCl2 and KNO3), three ionic strengths (0.03, 0.005 and soil ionic strength at field capacity, Is) and two soil liquid ratios (1:5 and 1:10) on the pH of 15 soils were investigated. pH measurements in solutions of ionic strength 0.005 differed the least from measurements made at Is. The differences that occurred in comparisons with distilled water or CaCl2 of ionic strength 0.03 (0.01 M) were much greater (20.4 pH units). An extractant with an ionic strength of 0.005 may provide a more realistic measure of pH in the field than distilled water or 0.01 M CaCl2 for West Australian soils.

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Altamash, Tausif, Wesam Ahmed, Saad Rasool e Kabir H. Biswas. "Intracellular Ionic Strength Sensing Using NanoLuc". International Journal of Molecular Sciences 22, n. 2 (12 gennaio 2021): 677. http://dx.doi.org/10.3390/ijms22020677.

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Intracellular ionic strength regulates myriad cellular processes that are fundamental to cellular survival and proliferation, including protein activity, aggregation, phase separation, and cell volume. It could be altered by changes in the activity of cellular signaling pathways, such as those that impact the activity of membrane-localized ion channels or by alterations in the microenvironmental osmolarity. Therefore, there is a demand for the development of sensitive tools for real-time monitoring of intracellular ionic strength. Here, we developed a bioluminescence-based intracellular ionic strength sensing strategy using the Nano Luciferase (NanoLuc) protein that has gained tremendous utility due to its high, long-lived bioluminescence output and thermal stability. Biochemical experiments using a recombinantly purified protein showed that NanoLuc bioluminescence is dependent on the ionic strength of the reaction buffer for a wide range of ionic strength conditions. Importantly, the decrease in the NanoLuc activity observed at higher ionic strengths could be reversed by decreasing the ionic strength of the reaction, thus making it suitable for sensing intracellular ionic strength alterations. Finally, we used an mNeonGreen–NanoLuc fusion protein to successfully monitor ionic strength alterations in a ratiometric manner through independent fluorescence and bioluminescence measurements in cell lysates and live cells. We envisage that the biosensing strategy developed here for detecting alterations in intracellular ionic strength will be applicable in a wide range of experiments, including high throughput cellular signaling, ion channel functional genomics, and drug discovery.

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Dickhout, Janneke, Rob Lammertink e Wiebe de Vos. "Membrane Filtration of Anionic Surfactant Stabilized Emulsions: Effect of Ionic Strength on Fouling and Droplet Adhesion". Colloids and Interfaces 3, n. 1 (10 gennaio 2019): 9. http://dx.doi.org/10.3390/colloids3010009.

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Membranes hold great potential to be used for the successful treatment of oily waste water, but membrane fouling leads to substantial decreases in performance. Here we study the impact of ionic strength on membrane fouling from an emulsion stabilized by the anionic surfactant sodium dodecyl sulfonate (SDS). For this we use a unique combinatorial approach where droplet adhesion to a cellulose surface in a flow cell is compared to membrane fouling (flux decline) on a cellulose membrane. In the initial membrane fouling stages droplet adhesion dominates. While the flow cell demonstrates a high number of droplets adhering especially at high ionic strengths (100 mM NaCl), the strongest flux decline is observed at intermediate (10 mM NaCl) ionic strength. This suggests that the fouling mechanism must be different, with pore blocking expecting to dominate at intermediate ionic strength. At the later fouling stages the porosity of the cake layer plays a key role in the flux reduction. At low ionic strength, oil droplets repel each other strongly and an open, more permeable, cake layer is formed. However at higher ionic strength, a screening of charge interactions leads to a lower porosity and thereby a lower flux. This leads to a clear trend: with a higher ionic strength a higher flux decline is observed. Flux recovery is high at all ionic strengths, in line with the observation in the flow cell that oil droplets can easily be sheared of a cellulose surface at all ionic strengths. This work thus highlights the critical effect of the ionic strength on membrane fouling by anionically stabilized emulsions. Moreover it shows how the use of an optical flow cell can provide key insights to help explain observations in more standard membrane fouling experiments.

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Borah, Priyanka, e Venkata S. K. Mattaparthi. "Effect of Ionic Strength on the Aggregation Propensity of Aβ1-42 Peptide: An In-silico Study". Current Chemical Biology 14, n. 3 (28 dicembre 2020): 216–26. http://dx.doi.org/10.2174/2212796814999200818103157.

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Background: Aggregation of misfolded proteins under stress conditions in the cell might lead to several neurodegenerative disorders. Amyloid-beta (Aβ1-42) peptide, the causative agent of Alzheimer’s disease, has the propensity to fold into β-sheets under stress, forming aggregated amyloid plaques. This is influenced by factors such as pH, temperature, metal ions, mutation of residues, and ionic strength of the solution. There are several studies that have highlighted the importance of ionic strength in affecting the folding and aggregation propensity of Aβ1-42 peptide. Objective: To understand the effect of ionic strength of the solution on the aggregation propensity of Aβ1-42 peptide, using computational approaches. Materials and Methods: In this study, Molecular Dynamics (MD) simulations were performed on Aβ1-42 peptide monomer placed in (i) 0 M, (ii) 0.15 M, and (iii) 0.30 M concentration of NaCl solution. To prepare the input files for the MD simulations, we have used the Amberff99SB force field. The conformational dynamics of Aβ1-42 peptide monomer in different ionic strengths of the solutions were illustrated from the analysis of the corresponding MD trajectory using the CPPtraj tool. Results: From the MD trajectory analysis, we observe that with an increase in the ionic strength of the solution, Aβ1-42 peptide monomer shows a lesser tendency to undergo aggregation. From RMSD and SASA analysis, we noticed that Aβ1-42 peptide monomer undergoes a rapid change in conformation with an increase in the ionic strength of the solution. In addition, from the radius of gyration (Rg) analysis, we observed Aβ1-42 peptide monomer to be more compact at moderate ionic strength of the solution. Aβ1-42 peptide was also found to hold its helical secondary structure at moderate and higher ionic strengths of the solution. The diffusion coefficient of Aβ1-42 peptide monomer was also found to vary with the ionic strength of the solution. We observed a relatively higher diffusion coefficient value for Aβ1-42 peptide at moderate ionic strength of the solution. Conclusion: Our findings from this computational study highlight the marked effect of ionic strength of the solution on the conformational dynamics and aggregation propensity of Aβ1-42 peptide monomer.

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Kosmulski, Marek, e Jarl B. Rosenholm. "High ionic strength electrokinetics". Advances in Colloid and Interface Science 112, n. 1-3 (dicembre 2004): 93–107. http://dx.doi.org/10.1016/j.cis.2004.09.005.

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Bucko, Sandra, Jaroslav Katona, Ljiljana Popovic, Zuzana Vastag e Lidija Petrovic. "Functional properties of pumpkin (Cucurbita pepo) seed protein isolate and hydrolysate". Journal of the Serbian Chemical Society 81, n. 1 (2016): 35–46. http://dx.doi.org/10.2298/jsc150615081b.

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Pumpkin seed protein isolate (PSPI) was enzymatically hydrolysed by pepsin to obtain pumpkin seed protein hydrolysate, PSPH. Investigation on solubility, interfacial and emulsifying properties of both PSPI and PSPH was conducted under different conditions of pH (3-8) and ionic strength (0-1 mol/dm3 NaCl). PSPI had the lowest solubility, i.e. isoelectric point (pI), at pH 5. PSPH had higher solubility than PSPI over whole range of pH and ionic strengths tested. Decrease in surface and interfacial tension evidenced that both PSPI and PSPH adsorb at air/protein solution and oil/protein solution interface. Emulsions (20 % oil in water) stabilized by 1 g/100cm3 PSPI or PSPH solution were prepared at pH 3, 5 and 8 and ionic strength of 0 and 0.5 mol/dm3 NaCl. PSPH stabilized emulsions from coalescence at all pH and ionic strengths tested. PSPI was able to stabilize emulsions at pH 3 and 0 mol/dm3 NaCl, and at pH 8 regardless of ionic strength, while emulsions at pH 5 and both 0 and 0.5 mol/dm3 NaCl and at pH 3 when ionic strength was increased separated to oil and serum layer immediately after preparation. All emulsions were susceptible to creaming instability.

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Manono, Malibongwe, Kirsten Corin e Jenny Wiese. "The Effect of the Ionic Strength of Process Water on the Interaction of Talc and CMC: Implications of Recirculated Water on Floatable Gangue Depression". Minerals 9, n. 4 (15 aprile 2019): 231. http://dx.doi.org/10.3390/min9040231.

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Previous studies speculate that hydroxo species present in flotation pulps at pH > 9, particularly those of polyvalent cations, selectively adsorb onto gangue minerals. Such species supposedly enhance the depressive action of carboxymethyl cellulose (CMC) onto gangue via an acid-base interaction between the positively charged mineral surface and the negatively charged CMC molecule. Thus, the hydrophilicity of gangue minerals is enhanced, preventing the dilution of the concentrate. However, as there is little evidence to support these claims for complex process waters of increasing ionic strength, it is important to investigate. Adsorption data and mineral surface charge analyses provide a fundamental understanding of how electrolytes and their ionic strengths affect gangue mineral-depressant adsorption. It is strongly anticipated that decoupling these effects will allow process operators to tailor their process water quality needs towards best flotation operating regimes and, in the long run, effect closed water circuits. Thus, using talc as a proxy for naturally floatable gangue common in sulfidic Cu–Ni–PGM ores, this work investigates the influence of the ionic strength of process water on the adsorption of CMC onto talc for a perspective on how saline water in sulfidic ores would affect the behavior and therefore management of floatable gangue. In the presence of CMC, the microflotation results showed that the rate of talc recovery decreased with increasing ionic strength of process water. Increases in ionic strength resulted in an increase in the adsorption of CMC onto talc. Talc particles proved to have been more coagulated at higher ionic strength since the settling time decreased with increasing ionic strength. Furthermore, the zeta potential of talc particles became less negative at higher ionic strengths of process water. It is thus proposed that increases in the ionic strength of process water increased the zeta potential of talc particles, enhancing the adsorption of CMC onto talc. This in turn created a more coagulated nature on talc particles, increasing their hydrophilicity and thereby retarding floatability.

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Sundman, Ola, Per Persson e Lars-Olof Öhman. "Comparison between specific surface complexation and Donnan ion-exchange models for describing the adsorption of cations on kraft fibres – literature evidence and EXAFS study of Cu(II) binding". Nordic Pulp & Paper Research Journal 25, n. 2 (1 maggio 2010): 178–84. http://dx.doi.org/10.3183/npprj-2010-25-02-p178-184.

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Abstract A compilation of the applied experimental conditions when studying metal ion adsorption onto kraft fibres, and the resulting conclusion, revealed that the ionic strength conditions used during the experiments were an important dividing factor. At low ionic strengths, the conclusion has regularly been that the Donnan ion-exchange model could correctly predict the adsorption while, at higher ionic strengths, it has often been concluded that the formation of specific metal-ion fibre complexes must be assumed. To study this apparent influence from the presence of monovalent sodium ions, Cu K-edge EXAFS spectra of Cu2+ ions adsorbed to kraft fibres were collected in media of “0” to 100 mM NaCl. Combined with previous data, these measurements confirmed that at very low ionic strength, the importance of specific interactions between the chemically modified cellulose fibres and the Cu(II) ions significantly decreased. For a detailed description of the adsorption phenomenon, both types of interactions must be considered simultaneously. For most technical and engineering applications, however, the Donnan model can be used at low ionic strength conditions, i.e. I ≲ 10 mM. At higher ionic strengths, though, the inclusion of specific complexes in the model is necessary for correctly describing the adsorption of di- and trivalent cations with strong complex forming properties.

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Homsher, E., F. Wang e J. R. Sellers. "Factors affecting movement of F-actin filaments propelled by skeletal muscle heavy meromyosin". American Journal of Physiology-Cell Physiology 262, n. 3 (1 marzo 1992): C714—C723. http://dx.doi.org/10.1152/ajpcell.1992.262.3.c714.

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The measurement of fluorescent-labeled actin filament movement driven by mechanoenzymes (e.g., myosin) is an important methodology for the study of molecular motors. It is assumed that the filament velocity (Vf) is analogous to the unloaded shortening velocity (Vu) seen in muscle fibers. Methods are described to reproducibly quantitate the movement of these filaments and to select uniformly moving filaments and specify their Vf. Use of these techniques allowed comparison of Vf to literature values for Vu with regard to [ATP], [ADP], [Pi], pH, ionic strength (10-150 mM), and temperature (15-30 degrees C). Vf and Vu are quantitatively similar with respect to the effects of substrate and product concentrations and temperatures greater than 20 degrees C. However, Vf is more sensitive to decreases in pH and temperatures less than 20 degrees C than Vu. At ionic strengths of 50-150 mM, Vf and Vu exhibit similar ionic strength dependencies (decreasing with ionic strength). At ionic strengths less than 50 mM, Vf is markedly reduced. Results of experiments using adenosine 5'-O-(3-thiotriphosphate) suggest that increasing the number of weakly bound cross bridges does not seriously affect Vf. Thus, although Vf is a good analogue for Vu under certain conditions (elevated ionic strength and temperatures greater than 20 degrees C), under others it is not. The results of motility assays must be cautiously interpreted.

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Huang, Lihua, Yehui Zhang e Haibin Li. "Self-Assembly of Rice Bran Globulin Fibrils in Electrostatic Screening: Nanostructure and Gels". Journal of Nanomaterials 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/951240.

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The effects of various ionic strengths and protein concentrations on the fibrils structure and gel properties of rice bran globulin (RBG) at pH 2.0 were investigated using atomic force microscopy (AFM), rheometer, and scanning electron microscope (SEM). AFM images showed the morphology of assembling RBG fibrils from strand beads to becoming branch clustered, when electrostatic repulsive forces attenuated gradually with increasing ionic strength. NaCl seems to accelerate the kinetics of fibrils formation, resulting in a significant increase in Th T fluorescence intensity. The increased ionic strengths promote particle size increasing and zeta potential decreasing synchronously. The percolation modelG'~C-Cpnbe used to calculate theoretical RBG gels concentration at various ionic strengths (0–500 mM), which decreased from 15.17 ± 0.63 to 2.26 ± 0.27 wt%. SEM images exhibited a granular mesh-like gel structure. A more homogenous structure occurred in low ionic strength. This study elucidates properties of RBG fibrils and gels as a bioactive material.

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Szuromi, Phil. "Speeding reactions through ionic strength". Science 372, n. 6545 (27 maggio 2021): 929.11–929. http://dx.doi.org/10.1126/science.372.6545.929-k.

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D’Amelio, Nicola, Benjamin Tanielian, Mourad Sadqi, Pilar López-Navajas e Victor Muñoz. "Cognate DNA Recognition by Engrailed Homeodomain Involves a Conformational Change Controlled via an Electrostatic-Spring-Loaded Latch". International Journal of Molecular Sciences 23, n. 5 (22 febbraio 2022): 2412. http://dx.doi.org/10.3390/ijms23052412.

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Transcription factors must scan genomic DNA, recognize the cognate sequence of their control element(s), and bind tightly to them. The DNA recognition process is primarily carried out by their DNA binding domains (DBD), which interact with the cognate site with high affinity and more weakly with any other DNA sequence. DBDs are generally thought to bind to their cognate DNA without changing conformation (lock-and-key). Here, we used nuclear magnetic resonance and circular dichroism to investigate the interplay between DNA recognition and DBD conformation in the engrailed homeodomain (enHD), as a model case for the homeodomain family of eukaryotic DBDs. We found that the conformational ensemble of enHD is rather flexible and becomes gradually more disordered as ionic strength decreases following a Debye–Hückel’s dependence. Our analysis indicates that enHD’s response to ionic strength is mediated by a built-in electrostatic spring-loaded latch that operates as a conformational transducer. We also found that, at moderate ionic strengths, enHD changes conformation upon binding to cognate DNA. This change is of larger amplitude and somewhat orthogonal to the response to ionic strength. As a consequence, very high ionic strengths (e.g., 700 mM) block the electrostatic-spring-loaded latch and binding to cognate DNA becomes lock-and-key. However, the interplay between enHD conformation and cognate DNA binding is robust across a range of ionic strengths (i.e., 45 to 300 mM) that covers the physiologically-relevant conditions. Therefore, our results demonstrate the presence of a mechanism for the conformational control of cognate DNA recognition on a eukaryotic DBD. This mechanism can function as a signal transducer that locks the DBD in place upon encountering the cognate site during active DNA scanning. The electrostatic-spring-loaded latch of enHD can also enable the fine control of DNA recognition in response to transient changes in local ionic strength induced by variate physiological processes.

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Carr, M. E., D. A. Gabriel e J. McDonagh. "Influence of Ca2+ on the structure of reptilase-derived and thrombin-derived fibrin gels". Biochemical Journal 239, n. 3 (1 novembre 1986): 513–16. http://dx.doi.org/10.1042/bj2390513.

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The effects of Ca2+ ion on the structure of thrombin-derived and reptilase-derived fibrin gels formed at various ionic strengths were studied turbidimetrically. For both enzymes clotting times were shorter, final gel turbidities were higher and fibre mass/length ratios were increased as the ionic strength was lowered. The addition of 5 mM-Ca2+ augmented each of these effects for any given ionic strength. In the thrombin system, Ca2+ increased the final gel turbidity from 0.04 to 0.26 A632.8 at ionic strength 0.15. Under identical conditions in the reptilase system, the final gel turbidity increased from 0.03 A632.8 in the absence of Ca2+ to 0.345 A632.8 in the presence of 5 mM-Ca2+. In the thrombin system, fibre mass/length ratios increased from 0.4 × 10(12) to 6.9 × 10(12) Da/cm in the absence of Ca2+, and from 4.4 × 10(12) to 7.9 × 10(12) Da/cm in the presence of Ca2+, as the ionic strengths were decreased from 0.15 to 0.08 and to 0.11 respectively. In the reptilase system, the mass/length ratios increased from 0.9 × 10(12) to 5.8 × 10(12) Da/cm in the absence of Ca2+, and from 4.8 × 10(12) to 8.7 × 10(12) Da/cm in the presence of Ca2+, as the ionic strengths were decreased from 0.15 to 0.08 and to 0.10 respectively. At ionic strengths below 0.10, the presence of 5 mM-Ca2+ caused precipitation and macroscopic aggregation of fibrinogen upon the addition of either enzyme. In the presence of 5 mM-Ca2+, the fibres composing thrombin-induced and reptilase-induced gels were virtually identical.

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Solis, JS, PM May e G. Hefter. "Cyanide Thermodynamics. III. Enthalpies and Entropies of Ionization of Water and Hydrogen Cyanide". Australian Journal of Chemistry 49, n. 6 (1996): 651. http://dx.doi.org/10.1071/ch9960651.

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The heats (enthalpy changes) associated with the ionization of water and of hydrogen cyanide have been determined by titration calorimetry at 25�C as a function of ionic strength up to 5 M in both NaCl and NaClO4 media. The enthalpy changes for both reactions exhibit a 'medium effect' with ?H being more positive in NaCl than in NaClO4 and with the difference becoming more pronounced with increasing ionic strength. This is attributed to the greater solvation of Cl- cf. CN- in aqueous solution. The present ?H values are similar to previous published results at high ionic strengths, and are in excellent agreement with the well established literature values at infinite dilution. The present ?H values were combined with literature stability constant data to calculate the corresponding entropies for the ionization of H2O and HCN as a function of ionic strength.

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Yanagibashi, Tomokazu, Motoyoshi Kobayashi e Keisuke Omori. "Application of Poly-γ-Glutamic Acid Flocculant to Flocculation–Sedimentation Treatment of Ultrafine Cement Suspension". Water 11, n. 9 (22 agosto 2019): 1748. http://dx.doi.org/10.3390/w11091748.

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We examined the effect of poly-γ-glutamic acid flocculant (PGAF) on the removal of ultrafine cement (UFC) particles stabilized by a poly-carboxylate co-polymer, which is a superplasticizer (SP). The flocculation–sedimentation treatment with PGAF successfully removed the SP-stabilized cement particles through the gravitational settling of the formed flocs. The removal efficiency reduced with the increase in the ionic strength, probably because of the shrunk form of poly-γ-glutamic acid (γ-PGA) at high ionic strengths. Increasing the mixing intensity during rapid mixing improved the removal efficiency. A series of flocculation–sedimentation experiments provided a diagram showing the relationship between ionic strengths and the addition amount of PGAF. Our results suggest that PGAF is a good candidate for the purification of cement suspension by flocculation–sedimentation, and a better removal performance can be obtained at lower ionic strengths with intense rapid mixing. From the diagram of the control charts presented in this study, we can determine the optimal addition amount of PGAF for achieving the target removal rate for cement suspension under any ionic strength.

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Wang, Yong, Jun Jiang, Ren-kou Xu e Diwakar Tiwari. "Phosphate adsorption at variable charge soil/water interfaces as influenced by ionic strength". Soil Research 47, n. 5 (2009): 529. http://dx.doi.org/10.1071/sr08181.

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The effect of phosphate adsorption on zeta potential of the colloids of variable charge soils and the effect of ionic strength on phosphate adsorption by the soils were investigated using batch experimental method. The presence of phosphate resulted in the decrease in zeta potential and isoelectric point (IEP) of the colloids of the soils, which further suggested that the phosphate was adsorbed specifically by these soils. The effect of phosphate adsorption on zeta potential was correlated with the content of free Fe/Al oxides in the soils; the higher the content of Fe/Al oxides in a soil the greater was the decrease in zeta potential and IEP of the soil colloids. The intersection of phosphate adsorption–pH curves at different ionic strengths (a characteristic pH) was obtained for 2 Oxisols. Above this pH, the adsorption of phosphate increased with increasing ionic strength, whereas below it the reverse trend occurred. The intersect pH was 4.60 for the Oxisol from Guangdong and 4.55 for the Oxisol from Yunnan, which was lower than the values of PZSE (point of zero salt effect) of these soils, but near the PZNC (point of zero net charge) of the soils. The effects of ionic strength and pH on phosphate adsorption by these soils were interpreted with the help of an adsorption model developed previously by Bowden et al. The results of zeta potential suggested that the potential in an adsorption plane became less negative with increasing ionic strength above the soil PZNC and decreased with increasing ionic strength below the soil PZNC. These results support the hypothesis of the adsorption model that the potential in the adsorption plane changed with ionic strength with an opposite trend to the surface charge of these soils. The phosphate adsorption by these soils was related not only to the ionic strength but also to the types of electrolytes present. K+ induced a greater increase in phosphate adsorption than Na+ due to the greater affinity of the soils to K+ than Na+.

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Rosenberg, Y. O., V. Metz, Y. Oren, Y. Volkman e J. Ganor. "Co-precipitation of radium in high ionic strength systems: 2. Kinetic and ionic strength effects". Geochimica et Cosmochimica Acta 75, n. 19 (ottobre 2011): 5403–22. http://dx.doi.org/10.1016/j.gca.2011.07.013.

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Lyacine, Bennacer, Kernou Nassim e Benmammar Djilali. "Laboratory Studies on the Influence of Ionic Strength on Particle Transport Behavior in a Saturated Porous Medium". Advanced Engineering Forum 49 (31 maggio 2023): 91–102. http://dx.doi.org/10.4028/p-xm3w08.

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An experimental study has been undertaken to investigate the effect of flow velocity and ionic strength on the transport of suspended particles (SP) and their deposition in a saturated porous medium. The SP injections were carried out using a laboratory column filled with sand and a pulse injection method. Ionic strengths varying between 0 and 600 mM (NaCl) have prospected. Two velocities were tested: 0.15 and 0.30 cm/s. Selected polydisperse particles diameters ranging from 0.27 to 5 μm and a median diameter (dp50) equal to 2.25 μm were used. An analytical solution of the convection–dispersion equation with first-order deposition kinetics was used to describe the experimental breakthrough curves and to identify the transport parameters. The results show that the increase of ionic strength promotes the retention of the SP in the porous medium. In addition, retention is more important when the flow velocity is low. The deposition kinetics coefficient increases with increasing ionic strength and flow velocity.

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Lai, Fu Kun, e Hua Li. "A Continuum Theory for Simulation of Ionic-Strength-Sensitive Hydrogel for BioMEMS Application". Advanced Materials Research 74 (giugno 2009): 21–24. http://dx.doi.org/10.4028/www.scientific.net/amr.74.21.

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A continuum multiphysics theory is presented for simulation of the ionic-strength-sensitive hydrogel and surrounding solution. The theory considers the coupled effects of chemical, electrical and mechanical multi-energy domains on the swelling behavior of the ionic-strength-sensitive hydrogel and is thus termed the multi-effect-coupling ionic-strength-stimuli (MECis) model. The MECis model consists of several governing equations, including Nernst-Planck flux system, Poisson equation, fixed charge density and mechanical equilibrium equation, in which the effect of the ionic strength is incorporated into the governing equation of diffusive flux and fixed charge. The theory is capable of simulating the swelling/shrinking behavior of smart hydrogel in buffer solution subject to the change in the ionic strength, and providing the distribution of the ionic concentration and electrical potential for applications of BioMEMS design. Apart from the ionic strength as the main stimulus, the influence of several parameters is discussed in detail, including the initial fixed charge density and Young’s modulus of the hydrogel.

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Minobe, S., T. Watanabe, T. Sato e T. Tosa. "Characteristics and applications of adsorbents for pyrogen removal". Biotechnology and Applied Biochemistry 10, n. 2 (aprile 1988): 143–53. http://dx.doi.org/10.1111/j.1470-8744.1988.tb00010.x.

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Characteristics and applications of immobilized histidine and immobilized histamine for pyrogen removal were investigated. Immobilized histidine showed a high affinity for pyrogen at low ionic strength and over a wide pH range. The adsorption capacity was 0.53 mg of lipopolysaccharide per milliliter of the adsorbent. The apparent dissociation constant was 1.57 × 10(‐9) M. The adsorption of pyrogen to immobilized histidine decreased with increasing ionic strength, but pyrogen could be adsorbed even at ionic strengths of gamma/2 = 0.05‐0.1, at which other substances were little adsorbed; that is, specific adsorption of pyrogen was observed. The adsorption of pyrogen could be increased at ionic strengths of gamma/2 = 0.05‐0.1 by using a lower flow rate or a longer column length. Immobilized histidine and immobilized histamine could be used for the removal of natural pyrogens contaminating various useful low‐molecular‐weight compounds as well as high‐molecular‐weight compounds such as proteins.

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Mocchiutti, Paulina, María V. Galván, María C. Inalbon e Miguel A. Zanuttini. "Improvement of paper properties of recycled unbleached softwood kraft pulps by poly(allylamine hydrochloride)". BioResources 6, n. 1 (3 gennaio 2011): 570–83. http://dx.doi.org/10.15376/biores.6.1.570-583.

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Polyelectrolytes containing amine functional groups such as PAH (poly(allylamine hydrochloride)) can be useful, under certain conditions, for improving paper strength. In this work, the charge density of PAH was determined at different pH and ionic strengths; PAH adsorption onto the cellulosic fibers was characterized, and the effects of low PAH dosage on the papermaking properties were evaluated. It was found that the ionization of PAH is complete in acid media, but it is partial and depends on the ionic strength in neutral media. The adsorption isotherms of PAH on a recycled pulp from kraft liner allowed us to determine the amount needed to saturate the adsorption capacity of the fibers. For the three ionic strengths analyzed, the swelling of the fibers decreased when PAH was added in an amount corresponding to saturation (0.23% PAH on dried pulp). Nevertheless, the swelling was recovered when the amount of PAH was the double the saturation level (0.46% PAH on dried pulp). At these levels of addition, the papermaking properties were clearly improved, especially compressive strengths SCT (short compressive test) and CMT (concora medium test). The Page equation of tensile strength showed that PAH improved the shear bond strength, while the relative bonding area slightly decreased.

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24

Busalmen, J. P., e S. R. de SÃ¯Â¿Â½nchez. "Adhesion of Pseudomonas fluorescens(ATCC 17552) to Nonpolarized and Polarized Thin Films of Gold". Applied and Environmental Microbiology 67, n. 7 (1 luglio 2001): 3188–94. http://dx.doi.org/10.1128/aem.67.7.3188-3194.2001.

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ABSTRACT The adhesion of Pseudomonas fluorescens (ATCC 17552) to nonpolarized and negatively polarized thin films of gold was studied in situ by contrast microscopy using a thin-film electrochemical flow cell. The influence of the electrochemical potential was evaluated at two different ionic strengths (0.01 and 0.1 M NaCl; pH 7) under controlled flow. Adhesion to nonpolarized gold surfaces readily increased with the time of exposition at both ionic-strength values. At negative potentials (−0.2 and −0.5 V [Ag/AgCl-KCl saturated {sat.}]), on the other hand, bacterial adhesion was strongly inhibited. At 0.01 M NaCl, the inhibition was almost total at both negative potentials, whereas at 0.1 M NaCl the inhibition was proportional to the magnitude of the potential, being almost total at −0.5 V. The existence of reversible adhesion was investigated by carrying out experiments under stagnant conditions. Reversible adhesion was observed only at potential values very close to the potential of zero charge of the gold surface (0.0 V [Ag/AgCl-KCl sat.]) at a high ionic strength (0.1 M NaCl). Theoretical calculations of the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy for the bacteria-gold interaction were in good agreement with experimental results at low ionic strength (0.01 M). At high ionic strength (0.1 M), deviations from DLVO behavior related to the participation of specific interactions were observed, when surfaces were polarized to negative potentials.

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25

Wu, F. Y., e S. B. Smith. "Ionic Strength and Myofibrillar Protein Solubilization". Journal of Animal Science 65, n. 2 (1 agosto 1987): 597–608. http://dx.doi.org/10.2527/jas1987.652597x.

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26

Punkkinen, Olli, Per Lyngs Hansen, Ling Miao e Ilpo Vattulainen. "DNA Overstretching Transition: Ionic Strength Effects". Biophysical Journal 89, n. 2 (agosto 2005): 967–78. http://dx.doi.org/10.1529/biophysj.105.063099.

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27

Biemans-Oldehinkel, E., N. A. B. N. Mahmood e B. Poolman. "A sensor for intracellular ionic strength". Proceedings of the National Academy of Sciences 103, n. 28 (30 giugno 2006): 10624–29. http://dx.doi.org/10.1073/pnas.0603871103.

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28

Pratt, P. L. "Strength and Deformation of Ionic Materials". Geophysical Journal of the Royal Astronomical Society 14, n. 1-4 (26 gennaio 2010): 5–11. http://dx.doi.org/10.1111/j.1365-246x.1967.tb06216.x.

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29

Liu, Boqun, Bert Poolman e Arnold J. Boersma. "Ionic Strength Sensing in Living Cells". ACS Chemical Biology 12, n. 10 (6 settembre 2017): 2510–14. http://dx.doi.org/10.1021/acschembio.7b00348.

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30

Nucara, Luca, Vincenzo Piazza, Francesco Greco, Valentina Robbiano, Valentina Cappello, Mauro Gemmi, Franco Cacialli e Virgilio Mattoli. "Ionic Strength Responsive Sulfonated Polystyrene Opals". ACS Applied Materials & Interfaces 9, n. 5 (27 gennaio 2017): 4818–27. http://dx.doi.org/10.1021/acsami.6b14455.

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31

Leberman, Reuben. "The Hofmeister series and ionic strength". FEBS Letters 284, n. 2 (24 giugno 1991): 293–94. http://dx.doi.org/10.1016/0014-5793(91)80707-a.

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32

Gibbs, Stephen J., Alice S. Chu, Edwin N. Lightfoot e Thatcher W. Root. "Ovalbumin diffusion at low ionic strength". Journal of Physical Chemistry 95, n. 1 (gennaio 1991): 467–71. http://dx.doi.org/10.1021/j100154a082.

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33

Jing Song Chang e S. Vigneswaran. "Ionic strength in deep bed filtration". Water Research 24, n. 11 (novembre 1990): 1425–30. http://dx.doi.org/10.1016/0043-1354(90)90164-2.

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34

Víctor, Cerdà, e Phansi Piyawan. "Buffer Solutions of known Ionic Strength". Annals of Advances in Chemistry 7, n. 1 (20 giugno 2023): 051–56. http://dx.doi.org/10.29328/journal.aac.1001043.

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Abstract (sommario):

pH buffer solutions are those in which minimal pH variations occur when moderate amounts of strong acids or bases are added or diluted. The most common buffers are those used in the intermediate pH zone and are made up of an acid-base conjugate pair (HA/A-), with Ca and Cb as analytical concentrations of acid and base respectively. The buffer capacity of a solution is the measure of its effectiveness in preserving the pH value when adding an acid or a base. Three new programs working under the Windows 10 environment have been developed. The first one, the BUFFER program, allows to prepare buffers of known ionic strength without the need of adding an inert electrolyte, calculating the pH and buffering capacity. On the other hand, the BRÖMSTED method allows calculating the pH of conjugated acid-base systems applying the Newton-Raphson method. In this work two more programs are described, one applying the Brömsted method to monoprotic acids and another new one to diprotic acids.

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35

Irigoyen, Joseba, Lulu Han, Irantzu Llarena, Zhenwei Mao, Changyou Gao e Sergio E. Moya. "Responsive Polyelectrolyte Multilayers Assembled at High Ionic Strength with an Unusual Collapse at Low Ionic Strength". Macromolecular Rapid Communications 33, n. 22 (30 agosto 2012): 1964–69. http://dx.doi.org/10.1002/marc.201200471.

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36

Jönsson, U., M. Malmqvist e I. Rönnberg. "Immobilization of immunoglobulins on silica surfaces. Kinetics of immobilization and influence of ionic strength". Biochemical Journal 227, n. 2 (15 aprile 1985): 373–78. http://dx.doi.org/10.1042/bj2270373.

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Abstract (sommario):

The kinetics of, and the influence of ionic strength on, the immobilization of rabbit immunoglobulin G (IgG) on different types of well-characterized silica surfaces were investigated. Adsorptive immobilization was compared with covalent attachment via thiol-disulphide exchange reactions. The amount of immobilized IgG on five different types of silica surfaces as a function of IgG concentration, at two different ionic strengths, was determined. The IgG-solid-surface interaction involved different types of interaction forces, depending on the surface chemistry of the solid surface. The solid-surface chemistry is an important parameter determining the immobilized amount of IgG. When conditions for covalent attachment of IgG to the surfaces were fulfilled, the IgG showed high affinity and the immobilized amount of IgG showed a fast saturation. Changes in ionic strength showed no significant influence on the kinetics of immobilization on these surfaces. The amount of covalently attached IgG was partially ionic-strength-dependent, indicating that adsorptive interactions were involved. The results are of fundamental interest for the development of new immunosensors based on surface-concentration-measuring devices.

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37

Souček, Jan, Emil Halámek e Roman Kysilka. "Atropine and quinine ionic associates with some acid dyes". Collection of Czechoslovak Chemical Communications 53, n. 8 (1988): 1655–63. http://dx.doi.org/10.1135/cccc19881655.

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Abstract (sommario):

The formation of ionic associates of atropine and quinine with bromothymol blue, metanil yellow and cresol red was studied by extraction spectrophotometry. In aqueous solutions, formation of ionic associates was only observed for quinine with bromothymol blue; ionic associates of both dyes with all of the three dyes could be, however, studied by their extraction into chloroform. The conditional extraction constants were calculated for the equilibria involved. The ability of atropine, quinine and bromothymol blue to be extracted into chloroform was examined in dependence on pH and ionic strength of the aqueous phase. The pH1/2 value corresponding to 50% extraction recovery decreases with increasing ionic strength for quinine whereas for atropine the extraction recovery is only slightly affected by a higher ionic strength and for bromothymol blue the pH1/2 (E = 50%) value increases with increasing ionic strength.

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38

Kuta, A. E., C. R. Reynolds e P. A. Henkart. "Mechanism of lysis by large granular lymphocyte granule cytolysin: generation of a stable cytolysin-RBC intermediate." Journal of Immunology 142, n. 12 (15 giugno 1989): 4378–84. http://dx.doi.org/10.4049/jimmunol.142.12.4378.

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Abstract The effect of ionic strength and pH on the hemolytic activity of large granular lymphocyte granule cytolysin was examined in detail. Cytolysin-mediated lysis of RBC was inhibited by either low ionic strength or low pH. Under these conditions a nonlytic cytolysin-RBC intermediate was formed as revealed by hemolysis when cytolysin pretreated cells were washed and resuspended at physiologic ionic strength and pH. Formation of the cytolysin-RBC intermediate at low ionic strength (250 mM sucrose), pH 7.3, required greater than 0.1 mM calcium. In contrast, formation of the intermediate at physiologic ionic strength (150 mM NaCl), pH 6.0, was calcium independent. Both types of intermediates were stable at 37 degrees C and required calcium to induce subsequent lysis. The degree of lysis of the intermediate generated at low ionic strength was similar to that measured under standard conditions with the use of either whole granule preparations or purified cytolysin. However, lysis of intermediates formed at pH 6.0 was much less efficient. Our data indicate that a stable cytolysin-RBC intermediate can be formed in which cytolysin is present in an unreactive state on the RBC surface; under conditions of physiologic ionic strength and calcium concentrations this intermediate rapidly lyses.

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39

Segovia-González, Xochitl Fabiola, Maria Veronica Villagrana-Escareño, Maricarmen Ríos-Ramírez, Vianey Santiago de la Cruz, Jessica Nathaly Mejía-Hernández, Jose Luis Cuellar-Camacho, Araceli Patrón-Soberano, Richard Sportsman e Jaime Ruiz-García. "An Observation of a Very High Swelling of Bromovirus Members at Specific Ionic Strengths and pH". Viruses 15, n. 10 (4 ottobre 2023): 2046. http://dx.doi.org/10.3390/v15102046.

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Abstract (sommario):

Cowpea chlorotic mottle virus (CCMV) and brome mosaic virus (BMV) are naked plant viruses with similar characteristics; both form a T = 3 icosahedral protein capsid and are members of the bromoviridae family. It is well known that these viruses completely disassemble and liberate their genome at a pH around 7.2 and 1 M ionic strength. However, the 1 M ionic strength condition is not present inside cells, so an important question is how these viruses deliver their genome inside cells for their viral replication. There are some studies reporting the swelling of the CCMV virus using different techniques. For example, it is reported that at a pH~7.2 and low ionic strength, the swelling observed is about 10% of the initial diameter of the virus. Furthermore, different regions within the cell are known to have different pH levels and ionic strengths. In this work, we performed several experiments at low ionic strengths of 0.1, 0.2, and 0.3 and systematically increased the pH in 0.2 increments from 4.6 to 7.4. To determine the change in virus size at the different pHs and ionic strengths, we first used dynamic light scattering (DLS). Most of the experiments agree with a 10% capsid swelling under the conditions reported in previous works, but surprisingly, we found that at some particular conditions, the virus capsid swelling could be as big as 20 to 35% of the original size. These measurements were corroborated by atomic force microscopy (AFM) and transmission electron microscopy (TEM) around the conditions where the big swelling was determined by DLS. Therefore, this big swelling could be an easier mechanism that viruses use inside the cell to deliver their genome to the cell machinery for viral replication.

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40

del Álamo, Marta, Germán Rivas e Mauricio G. Mateu. "Effect of Macromolecular Crowding Agents on Human Immunodeficiency Virus Type 1 Capsid Protein Assembly In Vitro". Journal of Virology 79, n. 22 (15 novembre 2005): 14271–81. http://dx.doi.org/10.1128/jvi.79.22.14271-14281.2005.

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ABSTRACT Previous studies on the self-assembly of capsid protein CA of human immunodeficiency virus type 1 (HIV-1) in vitro have provided important insights on the structure and assembly of the mature HIV-1 capsid. However, CA polymerization in vitro was previously observed to occur only at very high ionic strength. Here, we have analyzed the effects on CA assembly in vitro of adding unrelated, inert macromolecules (crowding agents), aimed at mimicking the crowded (very high macromolecular effective concentration) environment within the HIV-1 virion. Crowding agents induced fast and efficient polymerization of CA even at low (close to physiological) ionic strength. The hollow cylinders thus assembled were indistinguishable in shape and dimensions from those formed in dilute protein solutions at high ionic strength. However, two important differences were noted: (i) disassembly by dilution of the capsid-like particles was undetectable at very high ionic strength, but occurred rapidly at low ionic strength in the presence of a crowding agent, and (ii) a variant CA from a presumed infectious HIV-1 with mutations at the CA dimerization interface was unable to assemble at any ionic strength in the absence of a crowding agent; in contrast, this mutation allowed efficient assembly, even at low ionic strength, when a crowding agent was used. The use of a low ionic strength and inert macromolecules to mimic the crowded environment inside the HIV-1 virion may lead to a better in vitro evaluation of the effects of conditions, mutations or/and other molecules, including potential antiviral compounds, on HIV-1 capsid assembly, stability and disassembly.

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41

Irigoyen, Joseba, Jagoba Iturri, José Luis Camacho, Edwin Donath e Sergio Moya. "Polyelectrolyte brushes: Water Content, Zeta Potential and Mechanical Properties". MRS Proceedings 1754 (2015): 53–58. http://dx.doi.org/10.1557/opl.2015.470.

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Abstract (sommario):

ABSTRACTPolymer brushes of poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (PMETAC) and poly(sulfo propyl methacrylate) (PSPM) were synthesized by Atomic Transfer Radical Polymerization from planar and colloidal surfaces. Polymer brush growth was followed by QCMD and the water content determined by combined QCMD and elipsometry. From the water content the percentage of water lost during the brush collapse with the ionic strength could be obtained.Highly charged PSPM brushes were indented by Atomic Force Microscopy at different ionic strengths. The force response was fitted to a phenomenological equation analogous to the equation of state of a compressible fluid. Internal energy and brush compressibility were obtained as a function of ionic strength.Spherical brushes of PMETAC and PSPM display an invariance of the zeta potential with ionic strength in the range from 20 mM to 200 mM NaCl, the zeta potential remains almost constant. This invariance can be explained applying a hairy surface approach.

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42

Prot, T., L. Korving e M. C. M. Van Loosdrecht. "Ionic strength of the liquid phase of different sludge streams in a wastewater treatment plant". Water Science and Technology 85, n. 6 (15 febbraio 2022): 1920–35. http://dx.doi.org/10.2166/wst.2022.057.

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Abstract (sommario):

Abstract In a wastewater treatment plant (WWTP), several sludge streams exist and the composition of their liquid phase varies with time and place. For evaluating the potential for formation of precipitates and equilibria for weak acids/bases, the ionic strength and chemical composition need to be known. This information is often not available in literature, and even neglected in chemical model-based research. Based on a literature review, we proposed three ranges of concentration (low, typical and high) for the major constituents of the liquid phase of the different streams in a WWTP. The study also discusses the reasons for the concentration evolution, and the exceptional cases, to allow readers to consider the right range depending on their situation. The ionic strength of the different streams and the contribution of its constituents were calculated based on the ionic composition. The major contributors to the ionic strength for the wastewater-based streams (influent, effluent and mixed sludge) were Na+, Cl−, Mg2+ and Ca2+, representing 50–70% of the ionic strength. For digestate, and accounted for 65–75% of the ionic strength. Even though the ionic strength is recognized to impact several important wastewater treatment processes, its utilization in literature is not always adequate, which is discussed in this study.

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43

Zhang, Dong, Y. Q. Tang, R. L. Liu, D. Y. Li, Q. Y. Li e Wei Li. "“Genes” for material tailoring: Begin with the electron work function for MoC carbide modification—A first-principles study". Journal of Applied Physics 132, n. 13 (7 ottobre 2022): 135106. http://dx.doi.org/10.1063/5.0109067.

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Abstract (sommario):

This article reports a study on the modification of bulk and Young's moduli of MoC carbide by partially substituting Mo with selected metallic elements, which influence the strengths and contributions of covalent, ionic, and metallic bond components to the overall atomic bonding of the carbide and thus its mechanical properties. Electron work function (EWF) analysis demonstrates that this parameter plays a promising role as an indicator similar to an encoded parameter with material “genetic” information for guiding the substitute selection. The higher the carbide's EWF, the higher are its bulk and Young's moduli. A substitute having a higher EWF generally enhances the covalent bonding at the expense of ionic bonding. The covalent bond plays a primary role in determining the carbide's strength, while the ionic bonding also contributes to the strength to some degree. A substitute having a higher EWF enhances the metallic bonding, which improves the carbide's strength as well, although such a contribution is minor.

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44

Hubčík, L., P. Pullmannová, S. S. Funari, F. Devínsky e D. Uhríková. "DNA – DOPC – gemini surfactants complexes: effect of ionic strength". Acta Facultatis Pharmaceuticae Universitatis Comenianae 61, n. 2 (30 dicembre 2014): 26–34. http://dx.doi.org/10.2478/afpuc-2014-0013.

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Abstract (sommario):

AbstractThe effect of ionic strength on DNA condensation by cationic liposomes prepared as a mixture of ethane-1,2-diylbis(dodecyl-dimethylammonium bromide) (C2GS12) and dioleoylphosphatidylcholine (DOPC) was studied using fluorescence spectroscopy. The DNA condensation followed by changes in emission intensity of ethidium bromide shows a strong dependence on the ionic strength of the solution. At physiologically relevant ionic strength (0.15 mol/l NaCl), the amount of DNA condensed between lipid bilayers is approximately 40% lower compared to 0.005 mol/l NaCl. The structure of formed complexes was studied using small angle X-ray diffraction (SAXD). DNA–C2GS12–DOPC complexes form a condensed lamellar phase organisation, which is partially disrupted by the increase of ionic strength. Both the lamellar repeat distance and DNA–DNA distance show dependence on C2GS12/DOPC molar ratio, temperature and also on ionic strength. We found that the method of preparation significantly affects both the quality of organisation and the structural parameters of complexes as discussed in the paper.

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45

KRESKE, AUDREY C., KRISTIN BJORNSDOTTIR, FRED BREIDT e HOSNI HASSAN. "Effects of pH, Dissolved Oxygen, and Ionic Strength on the Survival of Escherichia coli O157:H7 in Organic Acid Solutions†‡". Journal of Food Protection 71, n. 12 (1 dicembre 2008): 2404–9. http://dx.doi.org/10.4315/0362-028x-71.12.2404.

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Abstract (sommario):

The ability of Escherichia coli O157:H7 to survive in acidified vegetable products is of concern because of previously documented outbreaks associated with fruit juices. A study was conducted to determine the survival of E. coli O157:H7 in organic acids at pH values typical of acidified vegetable products (pH 3.2 and 3.7) under different dissolved oxygen conditions (≤0.05 and 5 mg/liter) and a range of ionic strengths (0.086 to 1.14). All solutions contained 20 mM gluconic acid, which was used as a noninhibitory low pH buffer to compare the individual acid effect to that of pH alone on the survival of E. coli O157:H7. E. coli O157:H7 cells challenged in buffered solution with ca. 5-mg/liter dissolved oxygen (present in tap water) over a range of ionic strengths at pH 3.2 exhibited a decrease in survival over 6 h at 30°C as the ionic strength was increased. Cells challenged in 40 mM protonated l-lactic and acetic acid solutions with ionic strength of 0.684 achieved a >4.7-log CFU/ml reduction at pH 3.2. However, under oxygen-limiting conditions in an anaerobic chamber, with ≤0.05-mg/liter oxygen, E. coli O157:H7 cells showed ≤1.55-log CFU/ml reduction regardless of pH, acid type, concentration, or ionic strength. Many acid and acidified foods are sold in hermetically sealed containers with oxygen-limiting conditions. Our results demonstrate that E. coli O157:H7 may survive better than previously expected from studies with acid solutions containing dissolved oxygen.

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46

Giacobello, Fausta, Viviana Mollica-Nardo, Claudia Foti, Rosina Celeste Ponterio, Franz Saija, Sebastiano Trusso, Jiri Sponer, Giuseppe Cassone e Ottavia Giuffrè. "Hydrolysis of Al3+ in Aqueous Solutions: Experiments and Ab Initio Simulations". Liquids 2, n. 1 (3 marzo 2022): 26–38. http://dx.doi.org/10.3390/liquids2010003.

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Abstract (sommario):

An experimental and computational study on the hydrolysis of Al3+ in aqueous solutions is here reported. Speciation model and formation constants were determined by potentiometric titrations at T = 298.15 K, 0.1 ≤ I/mol L−1 ≤ 1 in aqueous NaCl, NaNO3, NaCl/NaNO3 solutions. The dependence of formation constants on ionic strength is reported in all the ionic media over the range of 0.1–1.0 mol L−1. Under the studied experimental conditions, the formation of Al3(OH)45+ and Al13(OH)327+ species is observed in all the investigated ionic media and ionic strengths. The formation constants of the species formed by Al3+ with Cl− were determined together with the dependence on the ionic strength. Moreover, with the aim of unveiling the molecular structure of the formed Al complexes, quantum-mechanical calculations and state-of-the-art ab initio molecular dynamics simulations under explicit solvation were executed. These computations show, for the first time, the highly cooperative role played by the surrounding water molecules in neutralising mononuclear systems–such as AlCl2+ and AlClOH+–and the hydrolytic polynuclear system, Al3(OH)45+.

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47

Tao, Jue Qiang, Wen Yan Lin, Xiao Hua Luo, Xin Qiu e Jin Hong Wu. "Compressive Strength Analysis of Ionic Soil Stabilizer Improving Soil". Key Engineering Materials 667 (ottobre 2015): 341–46. http://dx.doi.org/10.4028/www.scientific.net/kem.667.341.

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Abstract (sommario):

To explore the ionic liquid soil stabilizer improved soil mechanical properties, this experiment conducted liquid-plastic limit test and compaction test. On the basis of determining the optimal dosage of ionic soil stabilizer and mastering different mixture optimum moisture content and maximum dry density, the standard sample which consists of the Zhejiang red-brown clay and curing material including ionic soil stabilizer, cement and lime carried out the unconfined compressive strength test in different curing age and compaction degree. This paper analyzed the change reason of compaction and curing age about the stabilized soil. The results show that the ionic soil stabilizer has a significant effect on the compressive strength improvement of stabilized soil. Compared stabilized soil with traditional treatment soil, the compressive strength of stabilized soil has improved obviously with the increase of curing age and compaction degree. Research findings provide useful technical support and practice basis for promoting and applying ionic soil stabilizer in infrastructure construction.

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48

Kamel, Ahmed. "Ionic Strength and Drag Reduction of Polymers in Straight Pipes – An Experimental Investigation". Earth Science Research 10, n. 2 (22 maggio 2021): 23. http://dx.doi.org/10.5539/esr.v10n2p23.

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Previous work has tied the drag reduction properties of polymer solutions to type and concentration of salts, rather than its ionic strength, although it is a more extensive parameter to investigate the effects of salt contents on fluids behavior. The current study aims at investigating the relationship between ionic strength and drag reduction characteristics of polymer solutions when flowing in straight tubing. Nalco ASP-700 and ASP-820, two common anionic AMPS copolymers, are examined with various salts (2% KCl, 4% KCl, and synthetic seawater). Flow tests were conducted using a small-scale flow loop that includes a straight tubing with an outside diameter of 1.27 cm and a length of 4.57 m. It has been found that drag reduction performance of polymer solutions is well correlated with ionic strength, rather than salt type and/or concentration. With high ionic strength, lower drag reduction is noticed despite of the reduced salt concentration. Nevertheless, at higher Reynolds number, the effects of ionic strength minimizes. Both polymer solutions exhibit effective drag reduction characteristics and their behavior is greatly affected by polymer type, shear rate, and salt content. Correlations, with acceptable confidence level, between drag reduction ratio and solutions ionic strength are proposed. The correlations are strongly recommended to investigate the effects of salt types and/or concentrations, represented by its ionic strength on drag reduction behavior of polymer solutions in straight tubing.

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49

Saikaew, Wuthikorn, Supatpong Mattaraj e Ratana Jiraratananon. "Nanofiltration performance of lead solutions: effects of solution pH and ionic strength". Water Supply 10, n. 2 (1 aprile 2010): 193–200. http://dx.doi.org/10.2166/ws.2010.062.

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Nanofiltration performance (i.e. rejection and flux decline) of lead solutions was investigated using a dead-end test cell at room temperature. An aromatic polyamide NF-90 membrane was chosen to determine the impacts of solution chemistry. The experimental results revealed that solution flux decline was dependent on solution pH, ionic strength, and type of lead solutions. Solution flux conducted with different types of lead solutions (i.e. PbCl2 and Pb(NO3)2) decreased with increased solution pH. Solutions having high pH exhibited greater flux decline than those having low solution pH, while lead ion rejections were relatively high. Increased ionic strengths resulted in a greater flux decline, while lead ion rejections decreased with decreasing solution pH and increasing ionic strengths. Such results were related to low solution pH, suggesting an increase in fixed charge of proton (H+), decreasing electrical double layer thickness within membrane, thus allowing increased lead concentration passing through the membrane surface. Solution flux and rejection decreased further at higher ionic strengths, which caused a reduced negatively charged membrane, and thus decreased rejections. It was also found that lead ion for PbCl2 solution exhibited higher rejections than that of Pb(NO3)2 solution.

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50

Cortese, J. D., A. L. Voglino e C. R. Hackenbrock. "Ionic strength of the intermembrane space of intact mitochondria as estimated with fluorescein-BSA delivered by low pH fusion." Journal of Cell Biology 113, n. 6 (15 giugno 1991): 1331–40. http://dx.doi.org/10.1083/jcb.113.6.1331.

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Abstract (sommario):

The electrostatic interactions of cytochrome c with its redox partners and membrane lipids, as well as other protein interactions and biochemical reactions, may be modulated by the ionic strength of the intermembrane space of the mitochondrion. FITC-BSA was used to determine the relative value of the mitochondrial intermembrane ionic strength with respect to bulk medium external to the mitochondrial outer membrane. FITC-BSA exhibited an ionic strength-dependent fluorescence change with an affinity in the mM range as opposed to its pH sensitivity in the microM range. A controlled, low pH-induced membrane fusion procedure was developed to transfer FITC-BSA encapsulated in asolectin liposomes, to the intermembrane space of intact mitochondria. The fusion procedure did not significantly affect mitochondrial ultrastructure, electron transport, or respiratory control ratios. The extent of fusion of liposomes with the mitochondrial outer membrane was monitored by fluorescence dequenching assays using a membrane fluorescent probe (octadecylrhodamine B) and the soluble FITC-BSA fluorescent probe, which report membrane and contents mixing, respectively. Assays were consistent with a rapid, low pH-induced vesicle-outer membrane fusion and delivery of FITC-BSA into the intermembrane space. Similar affinities for the ionic strength-dependent change in fluorescence were found for bulk medium, soluble (9.8 +/- 0.8 mM) and intermembrane space-entrapped FITC-BSA (10.2 +/- 0.6 mM). FITC-BSA consistently reported an ionic strength in the intermembrane space of the functionally and structurally intact mitochondria within +/- 20% of the external bulk solution. These findings reveal that the intermembrane ionic strength changes as does the external ionic strength and suggest that cytochrome c interactions, as well as other protein interactions and biochemical reactions, proceed in the intermembrane space of mitochondria in the intact cell at physiological ionic strength, i.e., 100-150 mM.

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