Effect of high salt concentrations on water structure

Leberman, Reuben; Soper, A. K.

doi:10.1038/378364a0

Cited by 426 publications

(388 citation statements)

References 11 publications

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“…Upon desolvation, the hydration shell around the chaotrope is stripped off and allowed to regain the hydrogen bonds of the aqueous bulk 10. This rationalization is fully in line with the original classification of chaotropic ions as being “water‐structure breakers”,78 such that their desolvation (due to binding to other species) leads formally to a “water structure recovery” 10. As is the case with the debate on the origin of the hydrophobic effect, the interpretation of Hofmeister effects has been similarly controversial, with undeniable pieces of evidence in favor of water‐structure breaking effects of chaotropic ions in their solvation shell being known, for example, trends of viscosity B‐coefficients 79…”

Section: Thermochemical Hydration Characteristicssupporting

confidence: 77%

The Chaotropic Effect as an Assembly Motif in Chemistry

2018

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Following up on scattered reports on interactions of conventional chaotropic ions (for example, I−, SCN−, ClO4 −) with macrocyclic host molecules, biomolecules, and hydrophobic neutral surfaces in aqueous solution, the chaotropic effect has recently emerged as a generic driving force for supramolecular assembly, orthogonal to the hydrophobic effect. The chaotropic effect becomes most effective for very large ions that extend beyond the classical Hofmeister scale and that can be referred to as superchaotropic ions (for example, borate clusters and polyoxometalates). In this Minireview, we present a continuous scale of water–solute interactions that includes the solvation of kosmotropic, chaotropic, and hydrophobic solutes, as well as the creation of void space (cavitation). Recent examples for the association of chaotropic anions to hydrophobic synthetic and biological binding sites, lipid bilayers, and surfaces are discussed.

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Section: Thermochemical Hydration Characteristicssupporting

confidence: 77%

The Chaotropic Effect as an Assembly Motif in Chemistry

2018

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“…To facilitate vitrification of the bulk state of water, either NaK tartrate [sodium potassium tartrate, 0.9 M; mole fraction (moles salt/total moles) of 0.016 or hydration number R (moles H 2 O/moles salt) of 62] or NaCl (sodium chloride, 1.5 M; mole fraction of 0.027 or R of 37) were added. Although salt additives in water are known to perturb the structure (19)(20)(21)(22)(23) and glass-forming properties (24,25) of water, insight on the thermodynamic properties of pure water has been obtained from aqueous solutions (6,(26)(27)(28). Fig.…”

Section: Resultsmentioning

confidence: 99%

Glass-to-cryogenic-liquid transitions in aqueous solutions suggested by crack healing

Kim

Täte

Grüner

2015

Proc. Natl. Acad. Sci. U.S.A.

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Observation of theorized glass-to-liquid transitions between lowdensity amorphous (LDA) and high-density amorphous (HDA) water states had been stymied by rapid crystallization below the homogeneous water nucleation temperature (∼235 K at 0.1 MPa). We report optical and X-ray observations suggestive of glass-toliquid transitions in these states. Crack healing, indicative of liquid, occurs when LDA ice transforms to cubic ice at 160 K, and when HDA ice transforms to the LDA state at temperatures as low as 120 K. X-ray diffraction study of the HDA to LDA transition clearly shows the characteristics of a first-order transition. Study of the glass-toliquid transitions in nanoconfined aqueous solutions shows them to be independent of the solute concentrations, suggesting that they represent an intrinsic property of water. These findings support theories that LDA and HDA ice are thermodynamically distinct and that they are continuously connected to two different liquid states of water.glass-to-liquid transition | high-density amorphous ice | low-density amorphous ice | quenched HDA | first-order phase transition W ater has glassy states, including low-density amorphous (LDA) and high-density amorphous (HDA) ice (1-3). The glass-to-liquid transition in these polyamorphic forms of ice is the focus of theories proposed to explain anomalous properties of supercooled water (4-8). Although supporting experimental evidence exists (9-15), it remains controversial as the direct observation of a glass-to-liquid transition has been stymied by rapid crystallization below the homogeneous nucleation temperature (∼235 K at 0.1 MPa).In general, glasses are nonergodic, noncrystalline solids, in which atoms are fixed to their initial positions for macroscopically long periods of time (16). As is well known, when stress is applied, glasses can be cracked. Above the glass transition temperature, T g , the ergodic liquid is restored, and the stress-induced cracks in glasses can be healed by the diffusive motions of liquids. Indeed, it has been shown that the crack-healing process is reproducible and correlated with the glass transition temperatures, independent of liquid fragility (17, 18). ResultsBulk Water. In this study, crack healing is used to probe the molecular mobility in cryogenic transitions between glassy states of water or between glassy and crystalline states. Cracks do not heal for a sample held within any particular cryogenic solid state, indicating a low mobility in each of these states. Crack healing observed during phase transformations requires a high molecular mobility and is suggestive of an intermediate glass-to-liquid transition in the pathway between solid states. Fig. 1 shows the paths in a schematic phase diagram of water that were used to form and probe LDA and HDA ice. To facilitate vitrification of the bulk state of water, either NaK tartrate [sodium potassium tartrate, 0.9 M; mole fraction (moles salt/total moles) of 0.016 or hydration number R (moles H 2 O/moles salt) of 62] or NaCl (sodium chloride, 1.5 M; m...

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“…6), namely that more hydrated ions are effective at lower concentrations. The physico-chemical properties of salt solutions are certainly relevant to halophilic adaptation and they are currently the object of various studies (Bonnet6 and Leberman and Soper, 1995 …”

Section: Resultsmentioning

confidence: 99%

Stabilisation of Halophilic Malate Dehydrogenase from Haloarcula Marismortui by Divalent Cations

Madern

Zaccaı̈

1997

European Journal of Biochemistry

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Halophilic malate dehydrogenase is stable in a limited concentration range of MgC1, or CaCl,. Thermal deactivation of the protein at low concentrations of these divalent salts is very different from that occurring at high concentrations. In low salt, stability always increases as the temperature is lowered. In high salt, stability shows bell-shaped behaviour as a function of temperature: increasing to a maximum at 4"C, and subsequently decreasing as the temperature is lowered. This is in contrast to other salts, for which the deactivation behaviour depends on the salt type but not on its concentration. Cofactor addition or replacement of H,O by D,O modify only the deactivation at low MgC1, or CaCl, concentrations. A pH transition between pH 7 and pH 8, however, modified enzyme deactivation at both low and high MgCI, or CaCl, concentrations. The pH effect on stability was also observed in other salts. By comparing the effect of CaCl,, MgCI,, and NaC1, a strong correlation was found between the minimum salt concentration required for the stabilisation of halophilic malate dehydrogenase and the hydration of the cation.

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Effect of high salt concentrations on water structure

Cited by 426 publications

References 11 publications

The Chaotropic Effect as an Assembly Motif in Chemistry

The Chaotropic Effect as an Assembly Motif in Chemistry

Glass-to-cryogenic-liquid transitions in aqueous solutions suggested by crack healing

Stabilisation of Halophilic Malate Dehydrogenase from Haloarcula Marismortui by Divalent Cations

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