14 research outputs found

    One-Pot Synthesis of Strained Macrocyclic Pyridone Hexamers and Their High Selectivity toward Cu<sup>2+</sup> Recognition

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    The removal of Cu<sup>2+</sup> ions is relevant to environmental pollution control and neurodegenerative disease treatment. A novel family of strained macrocyclic pyridone hexamers, which exhibit highly selective recognition of Cu<sup>2+</sup> ions and reduce copper content in artificial seawater by 97% at a very low [host]:[CuCl<sub>2</sub>] molar ratio of 2:1, is documented

    Surprisingly High Selectivity and High Affinity in Mercury Recognition by H‑Bonded Cavity-Containing Aromatic Foldarands

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    In the absence of macrocyclic ring constraints, few synthetic systems, possessing a mostly solvent-independent well-folded conformation that is predisposed for highly selective and high affinity recognition of metal ions, have been demonstrated. We report here such a unique class of conformationally robust modularly tunable folding molecules termed foldarands that can recognize Hg<sup>2+</sup> ions surprisingly well over 22 other metal ions. Despite the lack of sulfur atoms and having only oxygen-donor atoms in its structure, the best foldarand molecule, i.e., tetramer <b>4</b>, exhibits a selectivity factor of at least 19 in differentiating the most tightly bound Hg<sup>2+</sup> ion from all other metal ions, and a binding capacity that is ≥18 times that of thio-crown ethers. These two noteworthy binding characters make possible low level removal of Hg<sup>2+</sup> ions. With a [<b>4</b>]:[Hg<sup>2+</sup>] molar ratio of 5:1 and a single biphasic solvent extraction, the concentration of Hg<sup>2+</sup> ions could be reduced drastically by 98% (from 200 to 4 ppb) in pure water. <b>4</b> could also effect a highly efficient reduction in mercury content by 98% (from 500 to 10 ppb) in artificial groundwater via multiple successive extractions with an overall consumption of <b>4</b> being 9:1 in terms of [<b>4</b>]:[Hg<sup>2+</sup>] molar ratio

    Polar Solvent-Induced Unprecedented Supergelation of (Un)Weathered Crude Oils at Room Temperature

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    Use of carrier solvents to assist dissolution of phase-selective organogelators (PSOGs) before application in oil gelation is a common approach for solution-based gelators. Because of the competition in H-bonds by the polar carrier solvent, decreased gelling ability of PSOGs was often observed. That is, while data are available, the previously documented biphasic minimum gelling concentrations (BMGCs) are much larger than the MGCs determined using heating–cooling cycle for the same PSOG against the same oil. In this study, we show that, by minimizing amount of polar carrier solvent used, the gelling ability of PSOGs actually can be enhanced very substantially, rather than being weakened. More specifically, we demonstrate that use of a minute amount of polar carrier solvents of different types (e.g., ethyl acetate, acetone, acetonitrile, and tetrahydrofuran) significantly enhances the gelling ability of seven structurally different organogelators in hydrophobic oil. In particular, with the use of 5 vol % essentially nontoxic ethyl acetate, application of this previously unexplored strategy onto four monopeptide-based PSOGs produces up to 11-fold improvement in biphasic gelling ability toward seven (un)­weathered crude oils of widely ranging viscosities. While collectively overcoming many problematic issues (slow gelling action, low gelling ability, or a need to use hot or toxic solvent for dissolution of gelator) associated with PSOGs, this surprisingly simple yet powerful and reliable method produces unprecedented rapid supergelation of crude oil at room temperature, with BMGCs of as low as 0.38 w/v % (e.g., 3.8 g per liter of crude oil) and an averaged reduction in material cost of gelators by 85–97%

    Surprisingly High Selectivity and High Affinity in Mercury Recognition by H‑Bonded Cavity-Containing Aromatic Foldarands

    No full text
    In the absence of macrocyclic ring constraints, few synthetic systems, possessing a mostly solvent-independent well-folded conformation that is predisposed for highly selective and high affinity recognition of metal ions, have been demonstrated. We report here such a unique class of conformationally robust modularly tunable folding molecules termed foldarands that can recognize Hg<sup>2+</sup> ions surprisingly well over 22 other metal ions. Despite the lack of sulfur atoms and having only oxygen-donor atoms in its structure, the best foldarand molecule, i.e., tetramer <b>4</b>, exhibits a selectivity factor of at least 19 in differentiating the most tightly bound Hg<sup>2+</sup> ion from all other metal ions, and a binding capacity that is ≥18 times that of thio-crown ethers. These two noteworthy binding characters make possible low level removal of Hg<sup>2+</sup> ions. With a [<b>4</b>]:[Hg<sup>2+</sup>] molar ratio of 5:1 and a single biphasic solvent extraction, the concentration of Hg<sup>2+</sup> ions could be reduced drastically by 98% (from 200 to 4 ppb) in pure water. <b>4</b> could also effect a highly efficient reduction in mercury content by 98% (from 500 to 10 ppb) in artificial groundwater via multiple successive extractions with an overall consumption of <b>4</b> being 9:1 in terms of [<b>4</b>]:[Hg<sup>2+</sup>] molar ratio

    Proton Gradient-Induced Water Transport Mediated by Water Wires Inside Narrow Aquapores of Aquafoldamer Molecules

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    Hollow tubular aquapores inside aquafoldamers can be created via the “sticky” end-mediated formation of 1D chiral helical stacks involving same-handed helices, and are capable of aligning H-bonded water molecules in a chain-like fashion. These aquapores uniquely feature a small cavity of ∼2.8 Å in diameter, a size identical to that of the water molecule and also comparable to the narrowest opening in naturally occurring aquaporins measuring ∼3 Å across, and hence allow not only proton transport but also unique proton-gradient-induced water transport across the lipid membranes in the presence of proton gradient

    Intramolecularly Hydrogen-Bonded Aromatic Pentamers as Modularly Tunable Macrocyclic Receptors for Selective Recognition of Metal Ions

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    Despite the tremendous progress that has been made in macrocyclic chemistry since the discovery of corands, cryptands, and spherands more than four decades ago, macrocyclic systems possessing a high level of controllability in structural configuration concurrent with a systematic tunability in function are still very rare. Employing an inner design strategy to orient H-bonding forces toward a macrocyclic cavity interior while convergently aligning exchangeable ion-binding building blocks that dictate a near-identical backbone curvature, we demonstrate here a novel pentagonal framework that not only enables its variable interior cavity to be maintained at near-planarity but also allows its ion-binding potential to be highly tunable. The H-bonded macrocyclic pentamers thus produced have allowed a systematic and combinatorial evolution of ion-selective pentamers for preferential recognition of Cs<sup>+</sup>, K<sup>+</sup>, or Ag<sup>+</sup> ions

    Low-Cost Phase-Selective Organogelators for Rapid Gelation of Crude Oils at Room Temperature

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    Frequent marine oil spills pose a significant threat to the environment and marine’s ecosystem. We have recently reported a highly tunable molecular gelling scaffold, which enables us to identify a few first examples of phase-selective organogelators (PSOGs) that can instantly gel the crude oil of various types with room-temperature operation. In this study, we demonstrate the high robustness and reliability of this modular gelling scaffold in consistently and combinatorially producing high capacity PSOGs. Such a unique feature has allowed us to carry out a systematic study of 48 gelators via a two-step screening process and to discover another powerful carboxybenzyl-based gelator with comparable gelling properties but with a cost lowered by more than 300%, pointing to a good commercial potential for rapid cleanup of oil spills while effectively eliminating environmental pollution caused by the spilled oil

    Rh(III)-Catalyzed Carboamination of Propargyl Cycloalkanols with Arylamines via Csp<sup>2</sup>–H/Csp<sup>3</sup>–Csp<sup>3</sup> Activation

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    A Rh­(III)-catalyzed carboamination of alkynyl cycloalkanols with arylamines has been developed. This transformation involves a novel Csp<sup>2</sup>–H/Csp<sup>3</sup>–Csp<sup>3</sup> activation relay and provides an efficient approach to versatile 1,2,3-trisubstituted indoles with a broad range of functional group tolerance

    Fusion Gene Vectors Allowing for Simultaneous Drug Selection, Cell Labeling, and Reporter Assay in Vitro and in Vivo

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    Vector systems allowing simultaneously for rapid drug selection, cell labeling, and reporter assay are highly desirable in biomedical research including stem cell biology. Here, we present such a vector system including pCVpf or pCVpr, plasmids that express <i>pf</i> or <i>pr</i>, a fusion protein between puromycin acetyltransferase and green or red fluorescent protein from CV, the human cytomegalovirus enhancer/promoter. Transfection with pCVpf or pCVpr produced a ∼10% efficiency of gene transfer. A 2-day pulse puromycin selection resulted in ∼13-fold enrichment for transgenic cells, and continuous puromycin selection produced stable transgenic stem cell clones with retained pluripotency. Furthermore, we developed a PAC assay protocol for quantification of transgene expression. To test the usefulness for cell labeling and PAC assay in vivo, we constructed pVASpf containing <i>pf</i> linked to the regulatory sequence of medaka germ gene <i>vasa</i> and generated transgenic fish with visible GFP expression in germ cells. PAC assay revealed the highest expression in the testis. Interestingly, PAC activity was also detectable in somatic organs including the eye, which was validated by fluorescence in situ hybridization. Therefore, the <i>pf</i> and <i>pr</i> vectors provide a useful system for simultaneous drug selection, live labeling, and reporter assay in vitro and in vivo
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