Un emploi de De chez Chrétien de Troyes

Englebert, Annick

doi:10.3406/roma.1991.1660

Cited by 8 publications

(12 citation statements)

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“…The Hofmeister series, however, does not correlate perfectly with ionic charge density: while lithium is smaller than sodium, lithium has a weaker Hofmeister effect. [37][38][39][40] In the present case, DODAB more easily displaced cesium than the lithium ion, meaning that Li + was more strongly bound to the silicon wafer than Cs + in clear agreement with expected results from the Hofmeister series. Certainly, in this case, counterion hydration is less important in determining the exchange between DODA cation and bound cation than the net ionic charge density.…”

Section: Discussionsupporting

confidence: 88%

“…The Hofmeister series is a list of ions rank-ordered in terms of how strongly they modulate the hydrophobicity of a nonpolar solute (hydrophobe) in a water solution. [37][38][39][40] Small ions tend to cause salting out, that is, they reduce hydrophobic solubilities in water, whereas large ions tend to cause salting-in, increasing nonpolar solubilities. The Hofmeister series, however, does not correlate perfectly with ionic charge density: while lithium is smaller than sodium, lithium has a weaker Hofmeister effect.…”

Section: Discussionmentioning

confidence: 99%

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Adsorption of Cationic Lipid Bilayer onto Flat Silicon Wafers: Effect of Ion Nature and Concentration

2006

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The effect of monovalent salt nature and concentration over a range of low ionic strengths (0-10 mM LiCl, NaCl, KCl, or CsCl) and at two different pH values (6.3 and 10.0) on adsorption of dioctadecyldimethylammonium bromide (DODAB) bilayer fragments (BF) onto flat SiO(2) surfaces was systematically evaluated by means of in situ ellipsometry. High-affinity adsorption isotherms fitted by the Langmuir model indicated that adsorption maxima were consistent with bilayer deposition only around 10 mM monovalent salt at both pH values. In pure water, the mean thickness of the DODAB adsorbed layer was close to zero with bilayer deposition taking place only around 10 mM ionic strength. In the presence of 10 mM CsCl or LiCl, the highest and the lowest affinity constants for DODAB adsorption onto SiO(2) were, respectively, obtained consistently with the expected facility of cation exchange at the surface required for DODAB adsorption. The cation more tightly bound to the solid surface should be Li(+), which would present the largest resistance to displacement by the DODAB cation, whereas the less tightly bound cation should be Cs(+) due to its largest ionic radius and lowest charge density. In other words, DODAB adsorption proceeds in accordance with charge density on the solid surface, which depends on the nature and concentration of bound counterions as well as DODAB cation ability to displace them. AFM images show a very smooth DODAB film adsorbed onto the surface in situ with a large frequency of BF auto-association from their edges. The present results for flat surfaces entirely agree with previous data from our group for DODAB adsorption onto silica particles.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Adsorption of Cationic Lipid Bilayer onto Flat Silicon Wafers: Effect of Ion Nature and Concentration

2006

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“…This water-water interaction energy becomes more attractive for salting-in ions and less attractive for saltingout ions, in contrast to what is proposed for chaotropes and kosmotropes. 25,26 In addition, Figure 3b shows that the strength of the hydrogen bond also become stronger as q is decreased. In both cases, the intersection of the curve with the value for pure water is not far from the transition between salting-in and salting-out behavior.…”

Section: Resultsmentioning

confidence: 97%

“…In addition, a theory based on the notion that kosmotropes induce stronger water-water interactions whereas chaotropes induce weaker water-water interactions has been argued to explain the salting effect on hydrophobic aggregation. 25,26 In this paper, we present results from molecular dynamics simulations correlating the ion-induced changes of structural and dynamical properties of water and the ability of these ions to alter the magnitude of the hydrophobic interaction. The results indicate that most of the properties of water in the salt solutions change monotonically with the ability of the salt to increase/ decrease the hydrophobic interaction.…”

Section: Introductionmentioning

confidence: 99%

“…Many of the ions that induce salting-out behavior also exhibit an increase in the viscosity of water. The interpertation was that these ions can induce more order in the structure of water, increasing the number of hydrogen bonds and thereby the water−water interaction energy. − On the other hand, Samoilov proposed a relation between the viscosity and the exchange rate of water molecules in the first solvation shell of the ion with bulk waters . Ions with high ionic charge density, binding surrounding waters stronger than water binds to itself, are characterized by positive activation free energy (of the exchange process) and are termed “positively hydrated”.…”

Section: Introductionmentioning

confidence: 99%

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Can Salting-In/Salting-Out Ions be Classified as Chaotropes/Kosmotropes?

2009

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Attempts to understand the Hofmeister Series at the molecular level has yielded numerous hypotheses, many of which refer to the way different salts modify the structural and dynamical properties of water. The most famous, and at the same time the most controversial, is the classification of cosolutes and ions as structure-breakers (chaotropes) or structure-makers (kosmotropes), and their identification as salting-in and salting-out agents, respectively. In this paper, we present results from molecular dynamics simulations correlating the ion-induced changes of the structural and dynamical properties of water and the ability of these ions to alter the magnitude of the hydrophobic interaction. Although most of the properties of water in the salt solutions change monotonically with the ability of the salt to increase/decrease the hydrophobic interaction, none of them is able to predict the transition from salting-in to salting-out, a prediction that was observed by the preferential binding/exclusion analysis. In addition, we find that the use of the terms, kosmotropes and chaotropes, is very misleading since the so-called kosmotropes can actually reduce the structure of water, whereas, the so-called chaotropes can increase the structure of water. Specifically, we find that the ability of the ions to reduce the hydrophobic interaction (a property attributed to chaotropes), correlates with their ability to increase the structure between the water molecules, including the number and strength of hydrogen bonds, and as a consequence, the water-water interaction energy (features attributed to kosmotropes). Nevertheless, the viscosity (as well as the rotational decay rate) of the water molecules decreases (increases) due to weaker binding to the ions. Thus, it is not the ion-induced structural ordering between the water molecules that affect the dynamical properties of water, but the strength of the ion-water interaction. Our results indicate that attempts to understand and predict salt-induced modulation of hydrophobic interactions only through the binary, salt-water, system is not possible.

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Urea–Water Solvation Forces on Prion Structures

Kleinjung¹,

Fraternali

2012

J. Chem. Theory Comput.

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Solvation forces are crucial determinants in the equilibrium between the folded and unfolded state of proteins. Particularly interesting are the solvent forces of denaturing solvent mixtures on folded and misfolded states of proteins involved in neurodegeneration. The C-terminal globular domain of the ovine prion protein (1UW3) and its analogue H2H3 in the α-rich and β-rich conformation were used as model structures to study the solvation forces in 4 M aqueous urea using molecular dynamics. The model structures display very different secondary structures and solvent exposures. Most protein atoms favor interactions with urea over interactions with water. The force difference between protein–urea and protein–water interactions correlates with hydrophobicity; i.e., urea interacts preferentially with hydrophobic atoms, in agreement with results from solvent transfer experiments. Solvent Shannon entropy maps illustrate the mobility gradient of the urea–water mixture from the first solvation shell to the bulk. Single urea molecules replace water in the first solvation shell preferably at locations of relatively high solvent entropy.

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Un emploi de De chez Chrétien de Troyes

Cited by 8 publications

References 0 publications

Adsorption of Cationic Lipid Bilayer onto Flat Silicon Wafers: Effect of Ion Nature and Concentration

Adsorption of Cationic Lipid Bilayer onto Flat Silicon Wafers: Effect of Ion Nature and Concentration

Can Salting-In/Salting-Out Ions be Classified as Chaotropes/Kosmotropes?

Urea–Water Solvation Forces on Prion Structures

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