Neutron scattering studies on the hydration of phosphate ions in aqueous solutions of K3PO4, K2HPO4 and KH2PO4

Mason, Philip E.; Cruickshank, J. M.; Neilson, G. W.; Buchanan, P

doi:10.1039/b306344e

Cited by 50 publications

(85 citation statements)

References 10 publications

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“…1(f), right). In agreement with the literature, 34,35 we find that the first solvation shell of H 2 PO − 4 consists of 12 water molecules, where ≈7.6 water molecules are located at the PO 2 coordination sites and form a tetrahedral environment of the oxygen atoms. Analysis of the P= =O· · · O W radial distribution function (rdf, Fig.…”

supporting

confidence: 78%

Ultrafast phosphate hydration dynamics in bulk H2O

Costard

Tyborski

Fingerhut

et al. 2015

The Journal of Chemical Physics

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Phosphate vibrations serve as local probes of hydrogen bonding and structural fluctuations of hydration shells around ions. Interactions of H2PO4− ions and their aqueous environment are studied combining femtosecond 2D infrared spectroscopy, ab-initio calculations, and hybrid quantum-classical molecular dynamics (MD) simulations. Two-dimensional infrared spectra of the symmetric (νS(PO2−)) and asymmetric (νAS(PO2−)) PO2− stretching vibrations display nearly homogeneous lineshapes and pronounced anharmonic couplings between the two modes and with the δ(P-(OH)2) bending modes. The frequency-time correlation function derived from the 2D spectra consists of a predominant 50 fs decay and a weak constant component accounting for a residual inhomogeneous broadening. MD simulations show that the fluctuating electric field of the aqueous environment induces strong fluctuations of the νS(PO2−) and νAS(PO2−) transition frequencies with larger frequency excursions for νAS(PO2−). The calculated frequency-time correlation function is in good agreement with the experiment. The ν(PO2−) frequencies are mainly determined by polarization contributions induced by electrostatic phosphate-water interactions. H2PO4−/H2O cluster calculations reveal substantial frequency shifts and mode mixing with increasing hydration. Predicted phosphate-water hydrogen bond (HB) lifetimes have values on the order of 10 ps, substantially longer than water-water HB lifetimes. The ultrafast phosphate-water interactions observed here are in marked contrast to hydration dynamics of phospholipids where a quasi-static inhomogeneous broadening of phosphate vibrations suggests minor structural fluctuations of interfacial water.

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supporting

confidence: 78%

Ultrafast phosphate hydration dynamics in bulk H2O

Costard

Tyborski

Fingerhut

et al. 2015

The Journal of Chemical Physics

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“…This is unlikely to correspond to a K or second O shell, as for solid samples K neighbors are located at distances g3.2 Å, 23,26,28 whereas for aqueous samples O water molecules are likely to reside at distances g3.7 Å. 7 For protonated samples, crystal structure data indicate H neighbors in the 2.2-2.5 Å region. However, the peak is also observed for nonprotonated samples, in addition to which protons are unlikely to scatter X-rays.…”

Section: Exafs the Experimental Kmentioning

confidence: 99%

“…7 Therefore PO 4 3-forms the strongest H bonds to water with a well-defined hydration sphere with ∼15 ( 3 water molecules. 7 This means that water molecules interact strongly with PO 4 3-in solution and these strong interactions are more likely to distort the PO 4 3-tetrahedron, relative to the increasingly weaker, less structured hydration spheres of the protonated anions. In addition, more H bonds in water are broken in the presence of kosmotropes, suggesting that the structure of H 2 O around the PO 4 3-anion is somewhat disrupted.…”

Section: Effect Of Protonation On the P-o Shell Exafs Analysis Resulmentioning

confidence: 99%

“…2 Phosphate speciation including structure and hydration of species in solution has been explored using techniques such as infrared (IR) and Raman spectroscopy 5,6 and neutron scattering. 7 Various theoretical approaches have also been applied to calculate the structures of phosphate species in solution. [8][9][10][11] Previous work using P X-ray absorption fine structure (XAFS) has focused primarily on interpretation of X-ray absorption near-edge (XANES) spectra [12][13][14][15] or extended X-ray absorption spectroscopy (EXAFS) in solid P samples.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

et al. 2009

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Phosphorus K-edge X-ray absorption fine structure (XAFS) was explored as a means to distinguish between aqueous and solid phosphates and to detect changes in phosphate protonation state. Data were collected for H 3 PO 4 , KH 2 PO 4 , K 2 HPO 4 and K 3 PO 4 solids and solutions and for the more complex phosphates, hydroxylapatite (HAP) and struvite (MAP). The X-ray absorption near-edge structure (XANES) spectra for solid samples are distinguishable from those of solutions by a shoulder at ∼4.5 eV above the edge, caused by scattering from cation sites. For phosphate species, the intensity of the white line peak increased for solid and decreased for aqueous samples, respectively, with phosphate deprotonation. This was assigned to increasing charge delocalization in solid samples, and the effect of solvating water molecules on charge for aqueous samples. In the extended X-ray absorption fine structure (EXAFS), backscattering from first-shell O atoms dominated the (k) spectra. Multiple scattering (MS) via a four-legged P-O 1 -P-O 1 -P collinear path was localized in the lower k region at ∼3.5 Å -1 and contributed significantly to the beat pattern of the first oscillation. For EXAFS analysis, increasing Debye-Waller factors suggest more disorder in the P-O shell with addition of protons to the crystal structure due to the lengthening effects of P-OH bonds. This disorder produces splitting in the hybridized P 3p-O 2p band in the density of states. For aqueous samples, however, increased protonation reduced the structural disorder within this shell. This was linked to a change from kosmotropic to chaotropic behavior of the phosphate species, with reduced effects of H bonding on structural distortion. The intensity of MS is correlated to the degree of disorder in the P-O shell, with more ordered structures exhibiting enhanced MS. The observed trends in the XAFS data can be used to distinguish between phosphate species in both solid and aqueous samples. This is applicable to many chemical, geochemical and biological systems, and may be an important tool for determining the behavior of phosphate during the hydrothermal gasification of biomass.

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“…Thus, its increased hydrated radius renders the passage through the pores of the dialysis membrane more difficult. Few investigations 5,6 have been carried out on the structure and dynamics of hydrogen bonds between the H 2 PO 4 − , HPO 4 2− , and PO 4 3− . Experimental data have been published on the hydration of P ions employing different techniques for the purpose of investigating the ion and its surroundings; moreover, the P-oxyanion features a higher charge (3 − ), 5,6 further slowing the passage through the dialysis membrane.…”

Section: Dialysismentioning

confidence: 99%

Phosphate control in dialysis

Cupisti¹,

Gallieni²,

Rizzo³

et al. 2013

IJNRD

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Prevention and correction of hyperphosphatemia is a major goal of chronic kidney disease-mineral and bone disorder (CKD-MBD) management, achievable through avoidance of a positive phosphate balance. To this aim, optimal dialysis removal, careful use of phosphate binders, and dietary phosphate control are needed to optimize the control of phosphate balance in well-nourished patients on a standard three-times-a-week hemodialysis schedule. Using a mixed diffusive-convective hemodialysis tecniques, and increasing the number and/or the duration of dialysis tecniques are all measures able to enhance phosphorus (P) mass removal through dialysis. However, dialytic removal does not equal the high P intake linked to the high dietary protein requirement of dialysis patients; hence, the use of intestinal P binders is mandatory to reduce P net intestinal absorption. Unfortunately, even a large dose of P binders is able to bind approximately 200-300 mg of P on a daily basis, so it is evident that their efficacy is limited in the case of an uncontrolled dietary P load. Hence, limitation of dietary P intake is needed to reach the goal of neutral phosphate balance in dialysis, coupled to an adequate protein intake. To this aim, patients should be informed and educated to avoid foods that are naturally rich in phosphate and also processed food with P-containing preservatives. In addition, patients should preferentially choose food with a low P-to-protein ratio. For example, patients could choose egg white or protein from a vegetable source. Finally, boiling should be the preferred cooking procedure, because it induces food demineralization, including phosphate loss. The integrated approach outlined in this article should be actively adapted as a therapeutic alliance by clinicians, dieticians, and patients for an effective control of phosphate balance in dialysis patients.

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Neutron scattering studies on the hydration of phosphate ions in aqueous solutions of K3PO4, K2HPO4 and KH2PO4

Cited by 50 publications

References 10 publications

Ultrafast phosphate hydration dynamics in bulk H2O

Ultrafast phosphate hydration dynamics in bulk H2O

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

Phosphate control in dialysis

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