Neptunium

Yoshida, Zenko; Johnson, Sylvia M.; Kimura, Takaumi; Krsul, J.R.

doi:10.1007/978-94-007-0211-0_6

Cited by 29 publications

(44 citation statements)

References 338 publications

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“…All the absorbance spectra are shown in Figure . We noticed a diminution of the absorbance at 980 nm (wavelength , characteristic of Np(V)) and a concomitant increase of the absorbance at 987 (attributed to the complexe between CaM WT and Np(V)) was observed. The isosbestic point at 984 nm was used to calculate the stability constant of the complex: log( K a ) = 4.85 ± 0.14.…”

Section: Resultsmentioning

confidence: 84%

“…Unlike uranyl, the neptunyl ion is not hydrolyzed at physiological pH; , therefore the experiments can be conducted at pH 7. In order to know the affinity of this actinide toward the protein of interest, a titration experiment was conducted, using neptunyl absorption spectra.…”

Section: Resultsmentioning

confidence: 99%

“…It is then mainly deposited in the kidney and bone tissue . Neptunium which is one of the most bioavailable minor-actinides produced in the nuclear fission reactor , is also of high interest. Its principal oxidation state in physiological condition is Np V (neptunyl NpO 2 + ), which makes it structurally comparable to uranyl.…”

Section: Introductionmentioning

confidence: 99%

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Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions

et al. 2016

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Because of their presence in the nuclear fuel cycle, neptunium and uranium are two actinides of main interest in case of internal contamination. Complexation of U(VI) and Np(V) by the target protein calmodulin (CaM(WT)) was therefore studied herein. Both actinides have two axial oxygen atoms, which, charge aside, makes them very similar structurally wise. This work combines spectroscopy and theoretical density functional theory (DFT) calculations. Structural characterization was performed by extended X-ray absorption fine structure (EXAFS) at the L(III)-edge for each studied actinide. Models for the binding site of the protein were developed and then refined by using DFT to fit the obtained experimental EXAFS data. The effect of hydrolysis was also considered for both actinides (the uranyl experiment was performed at pH 3 and 6, while the neptunyl experiment was conducted at pH 7 and 9). The effect of the pH variation was apparent on the coordination sphere of the uranyl complexes, while the neptunyl complex characteristics remained stable under both studied conditions. The DFT calculations showed that at near physiological pH the complex formed by CaM(WT) with the neptunium ion is more stable than the one formed with uranyl.

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Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 99%

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Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions

et al. 2016

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“…1,2 In these systems with [Rn]6d 1 5f n (uranium and neptunium) and [Rn]6d 0 5f n (plutonium) electronic configurations, the 5f valence shell electrons have a large spatial extension and are close in energy to the 6d electrons, making them prone to chemical bonding, in contrast with the 4f electrons of the lanthanides, which are more core-like. This character leads to a wide range of oxidation states, between +3 and +7, and the occurrence of magnetic ordering behavior.…”

Section: Introductionmentioning

confidence: 99%

A New Look at the Structural and Magnetic Properties of Potassium Neptunate K₂NpO₄ Combining XRD, XANES Spectroscopy, and Low-Temperature Heat Capacity

et al. 2017

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The physicochemical properties of the potassium neptunate K2NpO4 have been investigated in this work using X-ray diffraction, X-ray absorption near edge structure (XANES) spectroscopy at the Np-L3 edge, and low-temperature heat capacity measurements. A Rietveld refinement of the crystal structure is reported for the first time. The Np(VI) valence state has been confirmed by the XANES data, and the absorption edge threshold of the XANES spectrum has been correlated to the Mössbauer isomer shift value reported in the literature. The standard entropy and heat capacity of K2NpO4 have been derived at 298.15 K from the low-temperature heat capacity data. The latter suggest the existence of a magnetic ordering transition around 25.9 K, most probably of the ferromagnetic type.

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“…The investigation of the coordination chemistry and reactivity of neptunium in aqueous solution is a crucial but very difficult field of research . The challenge in studying neptunium compounds arises first from its radioactive nature.…”

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confidence: 99%

Rb₂[Ca(NpO₂)₂(PO₄)₂], the First Mixed Alkali–Alkaline Earth Metals Neptunyl(V) Phosphate: Crystal Chemistry and Sheet Stereoisomerism

Kohlgruber

Szymanowski

et al. 2018

Crystal Growth & Design

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A novel anhydrous neptunyl(V) compound, Rb 2 [Ca(NpO 2 ) 2 (PO 4 ) 2 ], was obtained by hydrothermal synthesis. It crystallizes in the orthorhombic space group Pbca with the unit-cell parameters a = 12.972(2), b = 13.213(3), c = 7.090(3) Å, V = 1215.3(6) Å 3 , Z = 4. The crystal structure is based on sheets of neptunyl and phosphate polyhedra representing a new geometrical isomer related to the uranophane-anion topology. The intercalation of calcium in octahedral coordination between adjacent sheets results in a heteropolyhedral framework. This phase is the first inorganic neptunyl compound containing both alkali and alkaline earth metals. The straightforward route used to obtain this compound offers interesting possibilities for the development of a new family of heteropolyhedral framework-type neptunyl oxysalts.

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Neptunium

Cited by 29 publications

References 338 publications

Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions

Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions

A New Look at the Structural and Magnetic Properties of Potassium Neptunate K₂NpO₄ Combining XRD, XANES Spectroscopy, and Low-Temperature Heat Capacity

Rb₂[Ca(NpO₂)₂(PO₄)₂], the First Mixed Alkali–Alkaline Earth Metals Neptunyl(V) Phosphate: Crystal Chemistry and Sheet Stereoisomerism

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Neptunium

Cited by 29 publications

References 338 publications

Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions

Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions

A New Look at the Structural and Magnetic Properties of Potassium Neptunate K2NpO4 Combining XRD, XANES Spectroscopy, and Low-Temperature Heat Capacity

Rb2[Ca(NpO2)2(PO4)2], the First Mixed Alkali–Alkaline Earth Metals Neptunyl(V) Phosphate: Crystal Chemistry and Sheet Stereoisomerism

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A New Look at the Structural and Magnetic Properties of Potassium Neptunate K₂NpO₄ Combining XRD, XANES Spectroscopy, and Low-Temperature Heat Capacity

Rb₂[Ca(NpO₂)₂(PO₄)₂], the First Mixed Alkali–Alkaline Earth Metals Neptunyl(V) Phosphate: Crystal Chemistry and Sheet Stereoisomerism