On the Solubility of Aliphatic Hydrocarbons in 7 M Aqueous Urea

Graziano, Giuseppe

doi:10.1021/jp004335e

Cited by 79 publications

(96 citation statements)

References 85 publications

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“…10,22,27,28 Several urea force fields exist in the literature. [10][11][12][13][14][29][30][31] Computational studies have reproduced the salting out effect ͑decrease in solute solubility͒ of urea solutions on methane and the noble gases, 27,32,33 illustrating that cavity formation is thermodynamically more unfavorable in urea solutions, which is supported by simple models of the salting in and out effects of urea solutions, 34 and in agreement with the observed experimental data on surface tension increases. 35 However, a recent comparison of urea force fields has appeared which demonstrates that current urea models display significantly different degrees of urea aggregation, 15 even though diffraction studies clearly show that urea does not disrupt the hydrogen bonding network of water.…”

Section: Introductionsupporting

confidence: 74%

Cavity formation and preferential interactions in urea solutions: Dependence on urea aggregation

Weerasinghe¹,

Smith²

2003

The Journal of Chemical Physics

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A series of models for 8 M urea solutions was investigated using molecular dynamics simulations. The models differed only in their charge distributions and displayed various degrees of urea aggregation. The relationship between urea aggregation and the thermodynamics of the solution was established using Kirkwood-Buff theory. It was observed that high urea aggregation resulted in lower predicted values for the solution activity, and that Kirkwood-Buff theory provided a sensitive test for the properties of a particular force field. The free energy for formation of repulsive cavities in the different solutions was also investigated. The free energy was more unfavorable than in pure water, but independent of the extent of urea aggregation. However, the preferential exclusion of urea from the cavities was very sensitive to the degree of urea aggregation and varied by more than an order of magnitude in response to changes in the activity derivatives. A simple explanation for these observations is presented.

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Section: Introductionsupporting

confidence: 74%

Cavity formation and preferential interactions in urea solutions: Dependence on urea aggregation

Weerasinghe¹,

Smith²

2003

The Journal of Chemical Physics

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“…Marcus has demonstrated that in aqueous solution, the component ions can be well represented by charged spheres having radii that are close to Pauling‐type crystal ionic radii with a coordination number of 6. We have calculated the values of

k_{c}

k_{i}

and

k_{γ}

for these salts by approximating ethane by a sphere having a radius of 2.19 Å and using the value of

g_{i}^{w a t e r} = - 20.1 k J {m o l}^{- 1}

as calculated by Jorgensen …”

Section: Resultsmentioning

confidence: 99%

Salt Effects on Hydrophobic Solvation: Is the Observed Salt Specificity the Result of Excluded Volume Effects or Water Mediated Ion‐Hydrophobe Association?

2020

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The solubility of hydrophobic molecules in water is sensitive to salt addition in an ion‐specific manner. Such “salting‐out” and “salting‐in” properties have been shown to be a major contributor to the measured ion‐specific Hofmeister effects that are observed in many biophysical phenomena. Various theoretical models have suggested a number of disparate mechanisms for salting‐out (salting‐in) of hydrophobic moieties, the most popular of which include preferential interaction, water‐mediated association, and electrostriction models. However, a complete molecular level description of this ion‐specificity is not yet available. This work investigates the ion‐specific nature of hydrophobic solvation by studying how sodium and chloride salts affect the thermodynamics of 1,2‐hexanediol micellization. The results of this study are analyzed in terms of scaled‐particle theory and we show that salt addition can affect hydrophobic solvation in two modalities: salt addition changes the cavitation free energy; salt addition also influences the solvent‐solute interaction energy by changing the hydration of the hydrophobic solute. These two effects are salt specific in nature and we suggest that for small hydrophobic solutes these effects are the main cause of salt‐specific Hofmeister effects on their solubility.

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“…Use of the CHARMM force field predicts that urea preferentially interacts with both amide and aliphatic hydrocarbon groups (CH 2 groups in the tri-glycine peptide); this supports the conclusion from several recent simulation studies [21, 22, 55] that interaction between urea and aliphatic groups also plays an important role in urea-induced denaturation. Quantitatively, however, comparison to experimental solubility [57, 58] and X-ray scattering [59] data indicates that the CHARMM force field and perhaps others likely overestimate the interaction between urea and aliphatic groups. Regarding GB, the present study finds that it is excluded mainly from the carboxylate groups and weakly from nonpolar groups, results which are consistent with recent experimental findings [7, 59].…”

Section: Discussionmentioning

confidence: 99%

Preferential Interactions between Small Solutes and the Protein Backbone: A Computational Analysis

Pegram

Record

et al. 2010

Biochemistry

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To help better understand the effects of small solutes on protein stability, we carry out atomistic simulations to quantitatively characterize the interactions between two broadly used small solutes, urea and glycine betaine (GB), with a tri-glycine peptide, which is a good model for protein backbone. Multiple solute concentrations are analyzed and each solute-peptide-water ternary system is studied with ~200–300 ns of molecular dynamics simulations with the CHARMM force field. The comparison between calculated preferential interaction coefficients (Γ23) and experimentally measured values suggests that semi-quantitative agreement with experiments can be obtained if care is exercised to balance interactions among the solute, protein and water. On the other hand, qualitatively incorrect (i.e., wrong sign in Γ23) result can be obtained if a solute model is constructed by directly taking parameters for chemically similar groups from existing force field. Such sensitivity suggests that small solute thermodynamic data can be valuable in the development of accurate force field models of biomolecules. Further decomposition of Γ23 into group contributions leads to additional insights regarding the effects of small solutes on protein stability. For example, use of the CHARMM force field predicts that urea preferentially interacts with not only amide groups in the peptide backbone but also aliphatic groups, suggesting a role for these interactions in urea-induced protein denaturation; quantitatively, however, it is likely that the CHARMM force field overestimates the interaction between urea and aliphatic groups. The results on GB support a simple thermodynamic model that assumes additivity of preferential interaction between GB and various biomolecular surfaces.

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On the Solubility of Aliphatic Hydrocarbons in 7 M Aqueous Urea

Cited by 79 publications

References 85 publications

Cavity formation and preferential interactions in urea solutions: Dependence on urea aggregation

Cavity formation and preferential interactions in urea solutions: Dependence on urea aggregation

Salt Effects on Hydrophobic Solvation: Is the Observed Salt Specificity the Result of Excluded Volume Effects or Water Mediated Ion‐Hydrophobe Association?

Preferential Interactions between Small Solutes and the Protein Backbone: A Computational Analysis

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