Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements

Rare earth elements (REEs) are critical materials to modern technologies. They are obtained by selective separation from mining feedstocks consisting of mixtures of their trivalent cation. We are developing an all-aqueous, bioinspired, interfacial separation using peptides as amphiphilic molecular extractants. Lanthanide binding tags (LBTs) are amphiphilic peptide sequences based on the EF-hand metal binding loops of calcium-binding proteins which complex selectively REEs. We study LBTs optimized for coordination to Tb<sup>3+</sup> using luminescence spectroscopy, surface tensiometry, X-ray reflectivity, and X-ray fluorescence near total reflection, and find that these LBTs capture Tb<sup>3+</sup> in bulk and adsorb the complex to the interface. Molecular dynamics show that the binding pocket remains intact upon adsorption. We find that, if the net negative charge on the peptide results in a negatively charged complex, excess cations are recruited to the interface by nonselective Coulombic interactions that compromise selective REE capture. If, however, the net negative charge on the peptide is -3, resulting in a neutral complex, a 1:1 surface ratio of cation to peptide is achieved. Surface adsorption of the neutral peptide complexes from an equimolar mixture of Tb<sup>3+</sup> and La<sup>3+</sup> demonstrates a switchable platform dictated by bulk and interfacial effects. The adsorption layer becomes enriched in the favored Tb<sup>3+</sup> when the bulk peptide is saturated, but selective to La<sup>3+</sup> for undersaturation due to a higher surface activity of the La<sup>3+</sup> complex.

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Publication Details

Journal
Proceedings of the National Academy of Sciences
Published
2024-12-19
DOI
https://doi.org/10.1073/pnas.2411763121
Citations
19
Primary Topic
Minerals Flotation and Separation Techniques
Type
article
Field-Weighted Citation Impact
3.83

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article

Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements

Kathleen J. Stebe, Eshe Hummingbird, Woo-Jin Jung, Mark L. Schlossman et al.
19 citations
Proceedings of the National Academy of Sciences
Minerals Flotation and Separation Techniques
3.83
article

Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements

Kathleen J. Stebe, Eshe Hummingbird, Woo-Jin Jung, Mark L. Schlossman, Charles Maldarelli, César de la Fuente‐Núñez, Stephen A. Crane, Felipe Jiménez‐Ángeles, Baofu Qiao, E. James Petersson, Robert J. Messinger, Ravi Radhakrishnan, S. Surabh, Wei Bu, Pan Sun, Mónica Olvera de la Cruz, Ivan J. Dmochowski, Raymond S. Tu, Mrinal K. Bera, Daeyeon Lee, Binhua Lin, Bikash Sapkota, Luis E. Ortuno Macias, Jason G. Marmorstein, Yiming Wang
article en
19 citations

Abstract

Rare earth elements (REEs) are critical materials to modern technologies. They are obtained by selective separation from mining feedstocks consisting of mixtures of their trivalent cation. We are developing an all-aqueous, bioinspired, interfacial separation using peptides as amphiphilic molecular extractants. Lanthanide binding tags (LBTs) are amphiphilic peptide sequences based on the EF-hand metal binding loops of calcium-binding proteins which complex selectively REEs. We study LBTs optimized for coordination to Tb<sup>3+</sup> using luminescence spectroscopy, surface tensiometry, X-ray reflectivity, and X-ray fluorescence near total reflection, and find that these LBTs capture Tb<sup>3+</sup> in bulk and adsorb the complex to the interface. Molecular dynamics show that the binding pocket remains intact upon adsorption. We find that, if the net negative charge on the peptide results in a negatively charged complex, excess cations are recruited to the interface by nonselective Coulombic interactions that compromise selective REE capture. If, however, the net negative charge on the peptide is -3, resulting in a neutral complex, a 1:1 surface ratio of cation to peptide is achieved. Surface adsorption of the neutral peptide complexes from an equimolar mixture of Tb<sup>3+</sup> and La<sup>3+</sup> demonstrates a switchable platform dictated by bulk and interfacial effects. The adsorption layer becomes enriched in the favored Tb<sup>3+</sup> when the bulk peptide is saturated, but selective to La<sup>3+</sup> for undersaturation due to a higher surface activity of the La<sup>3+</sup> complex.

Proceedings of the National Academy of SciencesVol. 121(52)
City College of New York (US), California University of Pennsylvania (US), University of Illinois Chicago (US), University of Chicago (US)
U.S. Department of Energy
Openalex Percentile: Top 6%
Minerals Flotation and Separation Techniques
3.83
DOIOpen Access PDFOpenAlex
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