Thermodynamics of ion hydration and its interpretation in terms of a common model

Marcus, Yizhak

doi:10.1351/pac198759091093

Cited by 87 publications

(89 citation statements)

References 7 publications

(10 reference statements)

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“…The partial molar volume V i 0 for a given anion in aqueous solution is directly proportional to its hydration free energy, ⌬G hydr (43). Moreover, the free energy of ion hydration is typically defined as its transfer from a fixed point in vacuum to a fixed point in the solution (44). The direct correlation between V i 0 and ⌬G hydr necessarily implies that B max and b are also linearly correlated to ⌬G hydr (see SI).…”

Section: Resultsmentioning

confidence: 99%

The inverse and direct Hofmeister series for lysozyme

Zhang

Cremer

2009

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

391

542

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Anion effects on the cloud-point temperature for the liquid؊liquid phase transition of lysozyme were investigated by temperature gradient microfluidics under a dark field microscope. It was found that protein aggregation in salt solutions followed 2 distinct Hofmeister series depending on salt concentration. Namely, under low salt conditions the association of anions with the positively charged lysozyme surface dominated the process and the phase transition temperature followed an inverse Hofmeister series. This inverse series could be directly correlated to the size and hydration thermodynamics of the anions. At higher salt concentrations, the liquid-liquid phase transition displayed a direct Hofmeister series that correlated with the polarizability of the anions. A simple model was derived to take both charge screening and surface tension effects into account at the protein/water interface. Fitting the thermodynamic data to this model equation demonstrated its validity in both the high and low salt regimes. These results suggest that in general positively charged macromolecular systems should show inverse Hofmeister behavior only at relatively low salt concentrations, but revert to a direct Hofmeister series as the salt concentration is increased.liquid-liquid phase transition ͉ protein aggregation P rotein-protein interactions can lead to aggregation. Such intermolecular contacts underlie the mechanistic basis for a variety of diseases (1-4) and are key to protein crystallization (5-7). An effective way to determine the strength of biomacromolecular interactions is to study the temperature-induced phase separation that occurs in concentrated protein solutions (8). When a concentrated protein solution is cooled below its cloud-point temperature, the system can separate into 2 coexisting liquid phases: 1 rich in protein and 1 poor. As coacervate droplets of the protein-rich phase grow, the solution turns cloudy (white) as a result of the scattering of visible light. Upon standing, the solution may completely separate by gravity into a protein-rich phase and a nearly pure aqueous phase above it. The temperature at which the initial cloud point occurs provides a simple physical measurement of the forces acting among biomacromolecules. Specifically, the higher the temperature at which the initial cloud point occurs, the stronger the putative attractive forces between the protein molecules should be.Dissolved salts in aqueous solutions have a strong influence on protein-protein interactions and the subsequent aggregated states which are formed. In fact, cloud-point temperatures typically follow a specific ion order according to the Hofmeister series (5,6,(9)(10)(11)(12)(13)(14). The relative effectiveness of anions to induce protein aggregation typically follows 1 of 2 trends depending on the pH of the solution (15, 16). Above a protein's isoelectric point, the macromolecule bears a net negative charge and a direct Hofmeister series is normally observed. In this case, chaotropes such as I Ϫ , ClO 4 Ϫ , and SCN Ϫ he...

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Section: Resultsmentioning

confidence: 99%

The inverse and direct Hofmeister series for lysozyme

Zhang

Cremer

2009

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

391

542

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“…Experimental hydration enthalpies measured for salts have to be assigned to separate anion and cation contributions. Literature values show significant variations, and therefore the data based on the TATB extrathermodynamic assumptions [48,49] have been taken for a comparison. The resulting hydration energies are -425 kcal mol -1 in the HF case and -420 kcal mol -1 in the DFT case, whereas the experimental value amounts are -383 kcal mol -1 [49].…”

Section: Structural Datamentioning

confidence: 99%

“…Literature values show significant variations, and therefore the data based on the TATB extrathermodynamic assumptions [48,49] have been taken for a comparison. The resulting hydration energies are -425 kcal mol -1 in the HF case and -420 kcal mol -1 in the DFT case, whereas the experimental value amounts are -383 kcal mol -1 [49]. In agreement with the nearly identical structural results of the two QM/MM MD simulations, the obtained hydration energies (∆E hydr ) are also very similar exhibiting a deviation of ~10 % from experimental results.…”

Section: Structural Datamentioning

confidence: 99%

Ab initio QM/MM MD simulations of the hydrated Ca2+ ion

Schwenk

Rode

2004

Pure and Applied Chemistry

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The comparison of two different combined quantum mechanical (QM)/molecular mechanical (MM) simulations treating the quantum mechanical region at Hartree-Fock (HF) and B3-LYP density functional theory (DFT) level allowed us to determine structural and dynamical properties of the hydrated calcium ion. The structure is discussed in terms of radial distribution functions, coordination number distributions, and various angular distributions and the dynamical properties, as librations and vibrations, reorientational times and mean residence times were evaluated by means of velocity autocorrelation functions. The QM/MM molecular dynamics (MD) simulation results prove an eightfold-coordinated complex to be the dominant species, yielding average coordination numbers of 7.9 in the HF and 8.0 in the DFT case. Structural and dynamical results show higher rigidity of the hydrate complex using DFT. The high instability of calcium ion's hydration shell allows the observation of water-exchange processes between first and second hydration shell and shows that the mean lifetimes of water molecules in this first shell (<100 ps) have been strongly overestimated by conclusions from experimental data.

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“…Marcus [16] has calculated the value of DH hyd = -6000 kJ mol -1 . Using thermodynamic data, he has evaluated for r i (Th 4+ ) = 1 Å the thickness of the hydration layer at 2.36 Å and the number of fixed water molecules at 14.…”

Section: Hydration Energy Of Thorium (Iv)mentioning

confidence: 99%

Physicochemical study of the hydrolysis of Rare-Earth elements (III) and thorium (IV)

Bentouhami

Bouet

Meullemeestre

et al. 2004

Comptes Rendus. Chimie

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The present work reports the hydrolysis of ions of the series of lanthanides (III) and actinide (IV) elements in dilute aqueous solutions. It has been systematically examined in the presence of sodium perchlorate, which has been used for maintaining the solution at constant ionic strength. The number, the nature of the species in solution and their hydrolysis constants logb 10i for all ions at I = 0.1 mol dm -3 and at 25°C were determined by different softwares: Superquad and Sirko_P. A pH-potentiometric method was used with glass electrodes to determine the equilibrium constants K i :n+ represents Ce 3+ , Pr 3+ , Nd 3+ , Eu 3+ , Sm 3+ and Th 4+ ions. For the lanthanides, hydrolysis increases with the increase of the atomic number and the contraction of the ionic radius. The Th 4+ ion undergoes significant hydrolysis. To cite this article: E. Bentouhami et al., C. R. Chimie 7 (2004). RésuméCette étude concerne l'hydrolyse des ions de la série lanthanides (III) et du thorium (IV) ; elle a été effectuée en présence de perchlorate de sodium, utilisé pour maintenir constante la force ionique des solutions I, égale à 0,1 mol dm -3 . Le nombre et la nature des espèces en solutions, ainsi que leurs constantes d'hydrolyse logb 10i , ont été déterminées à 25°C à l'aide de différents softwares de calculs, à savoir, Superquad et Sirko_P. Une méthode potentiométrique est utilisée sur électrode de verre pour déterminer les constantes d'équilibres K i :OH) (n−1)+ + H + où M n+ représente les ions Ce 3+ , Pr 3+ , Nd 3+ , Eu 3+ , Sm 3+ et Th 4+ . Pour les lanthanides, l'hydrolyse augmente avec le numéro atomique et la diminution du rayon atomique. On montre que l'ion Th 4+ subit l'hydrolyse de manière significative. Pour citer cet article : E. Bentouhami et al., C. R. Chimie 7 (2004).

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Thermodynamics of ion hydration and its interpretation in terms of a common model

Cited by 87 publications

References 7 publications

The inverse and direct Hofmeister series for lysozyme

The inverse and direct Hofmeister series for lysozyme

Ab initio QM/MM MD simulations of the hydrated Ca2+ ion

Physicochemical study of the hydrolysis of Rare-Earth elements (III) and thorium (IV)

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