Toward Engineering Intra-Receptor Interactions into Bis(crown ethers)

A synthetic receptor was designed in which cooperative binding of two crown ether moieties to an alkali metal ion simultaneously causes two hydrophobic substituents not involved in direct host-guest interactions to converge. Hydrophobic interactions between these substituents can be expected to contribute to the overall complex stability. Independent binding studies involving two diastereoisomers of this bis(crown ether), one in which intra-receptor interactions between the substituents are potentially possible and one in which they are not, using isothermal titration calorimetry showed that both isomers bind potassium ions in different solvent mixtures with the same overall affinity. Profound differences were observed for each isomer, however, in the enthalpies and entropies of binding, which are consistent with intra-receptor interactions in one compound. These interactions are counteracted by enthalpy-entropy compensation so that no overall improvement in cation affinity could be observed.

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Synthesis, photophysics, electrochemistry and metal ion-binding studies of rhenium(i) complexes with crown ether pendants: selective and specific binding properties for various metal ions

New Journal of Chemistry ◽

10.1039/b415951a ◽

2005 ◽

Vol 29 (1) ◽

pp. 165 ◽

Cited By ~ 12

Author(s):

Keith Man-Chung Wong ◽

Wei-Ping Li ◽

Kung-Kai Cheung ◽

Vivian Wing-Wah Yam

Keyword(s):

Crown Ether ◽

Metal Ions ◽

Metal Ion ◽

Specific Binding ◽

Ion Binding ◽

Metal Ion Binding ◽

Binding Studies ◽

Binding Properties

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PEO-based electrolytes blended with star polymers with precisely imprinted polymeric pseudo-crown ether cavities for alkali metal ion batteries

Journal of Membrane Science ◽

10.1016/j.memsci.2019.01.051 ◽

2019 ◽

Vol 576 ◽

pp. 182-189 ◽

Cited By ~ 25

Author(s):

Zhuliu Xiao ◽

Binghua Zhou ◽

Jirong Wang ◽

Cai Zuo ◽

Dan He ◽

...

Keyword(s):

Crown Ether ◽

Alkali Metal ◽

Metal Ion ◽

Star Polymers ◽

Alkali Metal Ion

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Axially‐ and Meso‐substituted Aza‐Crown‐Ether‐Incorporated BIII Subporphyrins: Control of Electron‐Donating Ability by Metal Ion Chelation

European Journal of Inorganic Chemistry ◽

10.1002/ejic.202100502 ◽

2021 ◽

Author(s):

Koki Kise ◽

Yu Jin Lee ◽

Takayuki Tanaka ◽

Dongho Kim ◽

Atsuhiro Osuka

Keyword(s):

Crown Ether ◽

Metal Ion ◽

Metal Ion Chelation ◽

Aza Crown Ether

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Identification and functional analysis of cadmium-binding protein in the visceral mass of Crassostrea gigas

Scientific Reports ◽

10.1038/s41598-021-90882-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Zehua Zheng ◽

Kazuhiro Kawakami ◽

Dingkun Zhang ◽

Lumi Negishi ◽

Mohamed Abomosallam ◽

...

Keyword(s):

Crassostrea Gigas ◽

Metal Ion ◽

Defense Mechanisms ◽

Three Dimensional ◽

Tryptophan Fluorescence ◽

Water Soluble ◽

Titration Calorimetry ◽

Visceral Mass ◽

The Pacific ◽

Liquid Chromatography Tandem Mass

AbstractThe Pacific oyster, Crassostrea gigas, is a traditional food worldwide. The soft body of the oyster can easily accumulate heavy metals such as cadmium (Cd). To clarify the molecular mechanism of Cd accumulation in the viscera of C. gigas, we identified Cd-binding proteins. 5,10,15,20-Tetraphenyl-21H,23H-porphinetetrasulfonic acid, disulfuric acid, tetrahydrate, and Cd-binding competition experiments using immobilized metal ion affinity chromatography revealed the binding of water-soluble high molecular weight proteins to Cd, including C. gigas protein disulfide isomerase (cgPDI). Liquid chromatography–tandem mass spectrometry (LC–MS/MS) analyses revealed two CGHC motifs in cgPDI. The binding between Cd and rcgPDI was confirmed through a Cd-binding experiment using the TPPS method. Isothermal titration calorimetry (ITC) revealed the binding of two Cd ions to one molecule of rcgPDI. Circular dichroism (CD) spectrum and tryptophan fluorescence analyses demonstrated that the rcgPDI bound to Cd. The binding markedly changed the two-dimensional or three-dimensional structures. The activity of rcgPDI measured by a PDI Activity Assay Kit was more affected by the addition of Cd than by human PDI. Immunological analyses indicated that C. gigas contained cgPDI at a concentration of 1.0 nmol/g (viscera wet weight). The combination of ITC and quantification results revealed that Cd-binding to cgPDI accounted for 20% of the total bound Cd in the visceral mass. The findings provide new insights into the defense mechanisms of invertebrates against Cd.

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Interbase-FRET binding assay for pre-microRNAs

Scientific Reports ◽

10.1038/s41598-021-88922-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Mattias Bood ◽

Anna Wypijewska del Nogal ◽

Jesper R. Nilsson ◽

Fredrik Edfeldt ◽

Anders Dahlén ◽

...

Keyword(s):

Ligand Binding ◽

Drug Targets ◽

Structural Changes ◽

Small Sample Size ◽

Resonance Energy ◽

Small Sample ◽

Titration Calorimetry ◽

Drug Candidate ◽

Binding Studies ◽

Aberrant Expression

AbstractThe aberrant expression of microRNAs (miRs) has been linked to several human diseases. A promising approach for targeting these anomalies is the use of small-molecule inhibitors of miR biogenesis. These inhibitors have the potential to (i) dissect miR mechanisms of action, (ii) discover new drug targets, and (iii) function as new therapeutic agents. Here, we designed Förster resonance energy transfer (FRET)-labeled oligoribonucleotides of the precursor of the oncogenic miR-21 (pre-miR-21) and used them together with a set of aminoglycosides to develop an interbase-FRET assay to detect ligand binding to pre-miRs. Our interbase-FRET assay accurately reports structural changes of the RNA oligonucleotide induced by ligand binding. We demonstrate its application in a rapid, qualitative drug candidate screen by assessing the relative binding affinity between 12 aminoglycoside antibiotics and pre-miR-21. Surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) were used to validate our new FRET method, and the accuracy of our FRET assay was shown to be similar to the established techniques. With its advantages over SPR and ITC owing to its high sensitivity, small sample size, straightforward technique and the possibility for high-throughput expansion, we envision that our solution-based method can be applied in pre-miRNA–target binding studies.

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Insights into the roles of charged residues in substrate binding and mode of action of mannuronan C-5 epimerase AlgE4

Glycobiology ◽

10.1093/glycob/cwab025 ◽

2021 ◽

Author(s):

Margrethe Gaardløs ◽

Sergey A Samsonov ◽

Marit Sletmoen ◽

Maya Hjørnevik ◽

Gerd Inger Sætrom ◽

...

Keyword(s):

Optical Tweezers ◽

Conformational Changes ◽

Molecular Mechanisms ◽

Hydrophobic Interactions ◽

Substrate Binding ◽

Interdisciplinary Approach ◽

Product Formation ◽

Titration Calorimetry ◽

Binding Groove ◽

Dynamics Simulations

Abstract Mannuronan C-5 epimerases catalyse the epimerization of monomer residues in the polysaccharide alginate, changing the physical properties of the biopolymer. The enzymes are utilized to tailor alginate to numerous biological functions by alginate-producing organisms. The underlying molecular mechanisms that control the processive movement of the epimerase along the substrate chain is still elusive. To study this, we have used an interdisciplinary approach combining molecular dynamics simulations with experimental methods from mutant studies of AlgE4, where initial epimerase activity and product formation were addressed with NMR spectroscopy, and characteristics of enzyme-substrate interactions were obtained with isothermal titration calorimetry and optical tweezers. Positive charges lining the substrate-binding groove of AlgE4 appear to control the initial binding of poly-mannuronate, and binding also seems to be mediated by both electrostatic and hydrophobic interactions. After the catalytic reaction, negatively charged enzyme residues might facilitate dissociation of alginate from the positive residues, working like electrostatic switches, allowing the substrate to translocate in the binding groove. Molecular simulations show translocation increments of two monosaccharide units before the next productive binding event resulting in MG-block formation, with the epimerase moving with its N-terminus towards the reducing end of the alginate chain. Our results indicate that the charge pair R343-D345 might be directly involved in conformational changes of a loop that can be important for binding and dissociation. The computational and experimental approaches used in this study complement each other, allowing for a better understanding of individual residues’ roles in binding and movement along the alginate chains.

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