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Selective Solid–Liquid Extraction of Lithium Cation Using Tripodal Sulfate-Binding Receptors Driven by Electrostatic Interactions

by Ya-Zhi Chen, Ying-Chun He, Li Yan, Wei Zhao and Biao Wu

Molecules 2024, 29(11), 2445; https://doi.org/10.3390/molecules29112445 - 22 May 2024

Viewed by 522

Abstract

Owing to the important role of and increasing demand for lithium resources, lithium extraction is crucial. The use of molecular extractants is a promising strategy for selective lithium recovery, in which the interaction between lithium and the designed extractant can be manipulated at the molecular level. Herein, we demonstrate that anion receptors of tripodal hexaureas can selectively extract Li₂SO₄ solids into water containing DMSO (0.8% water) compared to other alkali metal sulfates. The hexaurea receptor with terminal hexyl chains displays the best Li⁺ extraction selectivity at 2-fold over Na⁺ and 12.5-fold over K⁺. The driving force underpinning selective lithium extraction is due to the combined interactions of Li⁺-SO₄²⁻ electrostatics and the ion–dipole interaction of the lithium–receptor (carbonyl groups and N atoms); the latter was found to be cation size dependent, as supported by computational calculations. This work indicates that anion binding receptors could drive selective cation extraction, thus providing new insights into the design of receptors for ion recognition and separation. Full article

(This article belongs to the Section Inorganic Chemistry)

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17 pages, 2353 KiB

Open AccessArticle

C-Terminal-Modified Oligourea Foldamers as a Result of Terminal Methyl Ester Reactions under Alkaline Conditions

by Katarzyna Kedzia, Lukasz Dobrzycki, Marcin Wilczek and Karolina Pulka-Ziach

Int. J. Mol. Sci. 2023, 24(7), 6806; https://doi.org/10.3390/ijms24076806 - 6 Apr 2023

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Abstract

Hybrids of short oligourea foldamers with residues of α, β and γ-amino acids esters at the C-terminus were obtained and subjected to a reaction with LiOH. There are two possible transformations under such conditions, one of which is ester hydrolysis and the formation of a carboxylic group and the other is the cyclization reaction after abstraction of a proton from urea by a base. We have investigated this reaction with difference C-terminal residue structures, as well as under different work-up conditions, especially for oligourea hybrids with α-amino acid esters. For these compounds, an oligourea–hydantoin combination is the product of cyclization. The stability of the hydantoin ring under alkaline conditions has been alsotested. Furthermore, this work reports data related to the structure of C-terminal-modified oligourea foldamers in solution and, for one compound, in the solid state. Helical folding is preserved both for cyclized and linear modifications, with oligourea–acid hybrids appearing to be more conformationally stable, as they are stabilized by an additional intramolecular hydrogen bond in comparison to cyclic derivatives. Full article

(This article belongs to the Section Molecular Biology)

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13 pages, 13611 KiB

Open AccessArticle

Design of Oligourea-Based Foldamers with Antibacterial and Antifungal Activities

by Lorène Tallet, Emilie Frisch, Mégane Bornerie, Claire Medemblik, Benoît Frisch, Philippe Lavalle, Gilles Guichard, Céline Douat and Antoine Kichler

Molecules 2022, 27(5), 1749; https://doi.org/10.3390/molecules27051749 - 7 Mar 2022

Cited by 8 | Viewed by 2110

Abstract

There is an urgent need to develop new therapeutic strategies to fight the emergence of multidrug resistant bacteria. Many antimicrobial peptides (AMPs) have been identified and characterized, but clinical translation has been limited partly due to their structural instability and degradability in physiological environments. The use of unnatural backbones leading to foldamers can generate peptidomimetics with improved properties and conformational stability. We recently reported the successful design of urea-based eukaryotic cell-penetrating foldamers (CPFs). Since cell-penetrating peptides and AMPs generally share many common features, we prepared new sequences derived from CPFs by varying the distribution of histidine- and arginine-type residues at the surface of the oligourea helix, and evaluated their activity on both Gram-positive and Gram-negative bacteria as well as on fungi. In addition, we prepared and tested new amphiphilic block cofoldamers consisting of an oligourea and a peptide segment whereby polar and charged residues are located in the peptide segment and more hydrophobic residues in the oligourea segment. Several foldamer sequences were found to display potent antibacterial activities even in the presence of 50% serum. Importantly, we show that these urea-based foldamers also possess promising antifungal properties. Full article

(This article belongs to the Section Bioorganic Chemistry)

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