Nuclear Magnetic Resonance Spectroscopy of Aqueous Plutonium(IV) Desferrioxamine B Complexes

Boggs, Mark A.; Mason, Harris E.; Arai, Yuji; Powell, Brian A.; Kersting, Annie B.; Zavarin, Mavrik

doi:10.1002/ejic.201402105

Cited by 9 publications

(6 citation statements)

References 79 publications

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“…Characterization of the Cm 3+ complex allows determination of the number of coordinated solvent molecules per site, showing similarities to the lanthanides across a range of ionic radii. Importantly, we also show that lanmodulin outcompetes the An 3+ -binding siderophore desferrioxamine B (DFOB) for Cm 3+ over wide pH and concentration ranges, suggesting that LanM could play a more important role in actinide mobility in the environment than siderophores, which have been proposed as major species for complexing actinides in aquatic systems. − Our results (1) suggest that LanM may be a natural, macromolecular actinophore, (2) point to the environmental relevance of LanM and other similar proteins in actinide speciation in the environment, and (3) suggest new and preferential LanM-mediated separation methods for actinides.…”

Section: Introductionmentioning

confidence: 72%

“…Among the small ligands that have been studied for actinide binding in the environment, the siderophores have garnered significant attention since they are ubiquitous and are strong metal chelators. In particular, the tris-hydroxamate, desferrioxamine B (DFOB), has been extensively studied ,− and is often taken as a representative molecule of this class of ligands because it is widespread in nature, and it forms very strong complexes with plutonium ,, as well as with the trivalent lanthanides and actinides , (Table S6). It has been proposed that the DFOB complexes could represent as much as ∼30% of the speciation of trivalent lanthanides in seawater, even if present at subnanomolar concentration .…”

Section: Resultsmentioning

confidence: 99%

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Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment

et al. 2021

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Anthropogenic radionuclides, including long-lived heavy actinides such as americium and curium, represent the primary long-term challenge for management of nuclear waste. The potential release of these wastes into the environment necessitates understanding their interactions with biogeochemical compounds present in nature. Here, we characterize the interactions between the heavy actinides, Am3+ and Cm3+, and the natural lanthanide-binding protein, lanmodulin (LanM). LanM is produced abundantly by methylotrophic bacteria, including Methylorubrum extorquens, that are widespread in the environment. We determine the first stability constant for an Am3+-protein complex (Am3LanM) and confirm the results with Cm3LanM, indicating a ∼5-fold higher affinity than that for lanthanides with most similar ionic radius, Nd3+ and Sm3+, and making LanM the strongest known heavy actinide-binding protein. The protein’s high selectivity over 243Am’s daughter nuclide 239Np enables lab-scale actinide-actinide separations as well as provides insight into potential protein-driven mobilization for these actinides in the environment. The luminescence properties of the Cm3+-LanM complex, and NMR studies of Gd3+-LanM, reveal that lanmodulin-bound f-elements possess two coordinated solvent molecules across a range of metal ionic radii. Finally, we show under a wide range of environmentally relevant conditions that lanmodulin effectively outcompetes desferrioxamine B, a hydroxamate siderophore previously proposed to be important in trivalent actinide mobility. These results suggest that natural lanthanide-binding proteins such as lanmodulin may play important roles in speciation and mobility of actinides in the environment; it also suggests that protein-based biotechnologies may provide a new frontier in actinide remediation, detection, and separations.

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Section: Introductionmentioning

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment

et al. 2021

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“…During a spectro-potentiometric titration, another species (modeled as [Pu(IV) (HDFOB) (OH)] + ) formed at pH = 6.65. A subsequent NMR study argued against this speciation and instead proposed a [Pu(IV)DFOB-di-μ-OH-DFOBPu(IV)] occurring at pH 6.5 . It is possible that Pu(IV) could facilitate the deprotonation of the amine in the range of 4–6.65.…”

Section: Results and Discussionmentioning

confidence: 99%

“…A subsequent NMR study argued against this speciation and instead proposed a [Pu(IV)DFOB-di-μ-OH-DFOBPu(IV)] occurring at pH 6.5. 56 It is possible that Pu(IV) could facilitate the deprotonation of the amine in the range of 4−6.65. A direct interaction between the amine tail and the M(IV) ion is sterically less likely for Ti(IV) than for the larger Pu(IV) and Th(IV), but with its higher charge-to-radius ratio, Ti(IV) is the stronger Lewis acid.…”

Section: Inorganic Chemistrymentioning

confidence: 99%

Ti(IV) and the Siderophore Desferrioxamine B: A Tight Complex Has Biological and Environmental Implications

et al. 2017

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The siderophore desferrioxamine B (DFOB) binds Ti(IV) tightly and precludes its hydrolytic precipitation under biologically and environmentally relevant conditions. This interaction of DFOB with Ti(IV) is investigated by using spectro-potentiometric and spectro-photometric titrations, mass spectrometry, isothermal titration calorimetry (ITC), and computational modeling. The data from pH 2–10 suggest two one-proton equilibria among three species, with one species predominating below pH 3.5, a second from pH 3.5 to 8, and a third above pH 8. The latter species is prone to slow hydrolytic precipitation. Electrospray mass spectrometry allowed the detection of [Ti(IV) (HDFOB)]2+ and [Ti(DFOB)]+; these species were assigned as the pH < 3.5 and the 3.5 < pH < 8 species, respectively. The stability constant for Ti(IV)-DFOB was determined by using UV/vis-monitored competition with ethylenediaminetetraacetic acid (EDTA). Taking into consideration the available binding constant of Ti(IV) and EDTA, the data reveal values of log β111 = 41.7, log β110 = 38.1, and log β11–1 = 30.1. The former value was supported by ITC, with the transfer of Ti(IV) from EDTA to DFOB determined to be both enthalpically and entropically favorable. Computational methods yielded a model of Ti-DFOB. The physiological and environmental implications of this tight interaction and the potential role of DFOB in solubilizing Ti(IV) are discussed.

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“…The Pu stock was first purified using a Bio Rad AG 1-8X (100−200 mesh) resin column. 24 The Pu was converted to Pu(IV) using saturated NaNO 2 in 8 M nitric acid, heated to 50 °C and cooled to room temperature. The Pu(IV) was then loaded on a resin column and rinsed with 8 M nitric acid followed by 9 M HCl.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Reduction of Plutonium(VI) to (V) by Hydroxamate Compounds at Environmentally Relevant pH

Morrison

Jiao

Kersting

et al. 2018

Environ. Sci. Technol.

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Natural organic matter is known to influence the mobility of plutonium (Pu) in the environment via complexation and reduction mechanisms. Hydroxamate siderophores have been specifically implicated due to their strong association with Pu. Hydroxamate siderophores can also break down into di and monohydroxamates and may influence the Pu oxidation state, and thereby its mobility. In this study we explored the reactions of Pu(VI) and Pu(V) with a monohydroxamate compound (acetohydroxamic acid, AHA) and a trihydroxamate siderophore desferrioxamine B (DFOB) at an environmentally relevant pH (5.5-8.2). Pu(VI) was instantaneously reduced to Pu(V) upon reaction with AHA. The presence of hydroxylamine was not observed at these pHs; however, AHA was consumed during the reaction. This suggests that the reduction of Pu(VI) to Pu(V) by AHA is facilitated by a direct one electron transfer. Importantly, further reduction to Pu(IV) or Pu(III) was not observed, even with excess AHA. We believe that further reduction of Pu(V) did not occur because Pu(V) does not form a strong complex with hydroxamate compounds at a circum-neutral pH. Experiments performed using desferrioxamine B (DFOB) yielded similar results. Broadly, this suggests that Pu(V) reduction to Pu(IV) in the presence of natural organic matter is not facilitated by hydroxamate functional groups and that other natural organic matter moieties likely play a more prominent role.

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Nuclear Magnetic Resonance Spectroscopy of Aqueous Plutonium(IV) Desferrioxamine B Complexes

Cited by 9 publications

References 79 publications

Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment

Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment

Ti(IV) and the Siderophore Desferrioxamine B: A Tight Complex Has Biological and Environmental Implications

Reduction of Plutonium(VI) to (V) by Hydroxamate Compounds at Environmentally Relevant pH

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