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Biological Reduction of a U(V)-Organic Ligand Complex.

ABSTRACT: Metal-reducing microorganisms such as Shewanella oneidensis MR-1 reduce highly soluble species of hexavalent uranyl (U(VI)) to less mobile tetravalent uranium (U(IV)) compounds. The biologically mediated immobilization of U(VI) is being considered for the remediation of U contamination. However, the mechanistic underpinnings of biological U(VI) reduction remain unresolved. It has become clear that a first electron transfer occurs to form pentavalent (U(V)) intermediates, but it has not been definitively established whether a second one-electron transfer can occur or if disproportionation of U(V) is required. Here, we utilize the unusual properties of dpaea^2- ((dpaeaH₂═bis(pyridyl-6-methyl-2-carboxylate)-ethylamine)), a ligand forming a stable soluble aqueous complex with U(V), and investigate the reduction of U(VI)-dpaea and U(V)-dpaea by S. oneidensis MR-1. We establish U speciation through time by separating U(VI) from U(IV) by ion exchange chromatography and characterize the reaction end-products using U M₄-edge high resolution X-ray absorption near-edge structure (HR-XANES) spectroscopy. We document the reduction of solid phase U(VI)-dpaea to aqueous U(V)-dpaea but, most importantly, demonstrate that of U(V)-dpaea to U(IV). This work establishes the potential for biological reduction of U(V) bound to a stabilizing ligand. Thus, further work is warranted to investigate the possible persistence of U(V)-organic complexes followed by their bioreduction in environmental systems.

SUBMITTER: Molinas M

PROVIDER: S-EPMC8154365 | biostudies-literature | 2021 Apr

REPOSITORIES: biostudies-literature

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Biological Reduction of a U(V)-Organic Ligand Complex.

Molinas Margaux M Faizova Radmila R Brown Ashley A Galanzew Jurij J Schacherl Bianca B Bartova Barbora B Meibom Karin L KL Vitova Tonya T Mazzanti Marinella M Bernier-Latmani Rizlan R

Environmental science & technology 20210311 8

Metal-reducing microorganisms such as <i>Shewanella oneidensis</i> MR-1 reduce highly soluble species of hexavalent uranyl (U(VI)) to less mobile tetravalent uranium (U(IV)) compounds. The biologically mediated immobilization of U(VI) is being considered for the remediation of U contamination. However, the mechanistic underpinnings of biological U(VI) reduction remain unresolved. It has become clear that a first electron transfer occurs to form pentavalent (U(V)) intermediates, but it has not be ...[more]

PMID: 33705103

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Biological Reduction of a U(V)-Organic Ligand Complex.

Publications

Biological Reduction of a U(V)-Organic Ligand Complex.

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