Cucurbituril as a ligand for the complexation of cations in aqueous solutions

Buschmann, Hans‐Jürgen; Cleve, E.; Schollmeyer, Eckhard

doi:10.1016/s0020-1693(00)83800-1

Cited by 156 publications

(153 citation statements)

References 20 publications

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“…37 The latter are capable, not only for CB7 but also for its homologues, of binding inorganic cations as well as the cationic sites of organic guests, mostly ammonium groups; nonpolar groups are preferentially immersed in the inner cavity. [38][39][40][41][42] CB7 and its larger homologue CB8 have been shown to bind aromatic amino acids and sequence-specifically to peptides and proteins containing phenylalanine (Phe), tryptophan (Trp), or tyrosine (Tyr) at the N-terminal positions. [43][44][45][46][47] Recognition at the N terminus is achieved via the cooperation of hydrophobic inclusion of the aromatic side chain and electrostatic stabilization of the proximal N-terminal ammonium group.…”

Section: Resultsmentioning

confidence: 99%

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

et al. 2011

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An analytical method has been developed for the continuous monitoring of protease activity on unlabelled peptides in real time by fluorescence spectroscopy. The assay is enabled by a reporter pair comprising the macrocycle cucurbit [7]uril (CB7) and the fluorescent dye acridine orange (AO). CB7 functions by selectively recognizing N-terminal phenylalanine residues as they are produced during the enzymatic cleavage of enkephalintype peptides by the metalloendopeptidase thermolysin. The substrate peptides (e.g., ThrGly-Ala-Phe-Met-NH2) bind to CB7 with moderately high affinity (K ca. 10 4 M -1 ), while their cleavage products (e.g., Phe-Met-NH2) bind very tightly (K > 10 6 M -1 ). AO signals the reaction upon its selective displacement from the macrocycle by the high affinity product of proteolysis. The resulting supramolecular tandem enzyme assay effectively measures the kinetics of thermolysin, including the accurate determination of sequence specificity (Ser and Gly instead of Ala), stereospecificity (DAla instead of LAla), endo-versus exopeptidase activity (indicated by differences in absolute fluorescence response), and sensitivity to terminal charges (-CONH2 versus -COOH). The capability of the tandem assay to measure protease inhibition constants was demonstrated on phosphoramidon as a known inhibitor to afford an inhibition constant of (17.8 ± 0.4) nM. This robust and label-free approach to the study of protease activity and inhibition should be transferable to other endo-and exopeptidases that afford products with N-terminal aromatic amino acids.2

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Section: Resultsmentioning

confidence: 99%

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

et al. 2011

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“…This fact is easily understood once, as already mentioned, K + ions form very stable coordination compounds with cucurbiturils. 39 The presence of the nanodisks was confirmed by AFM imaging, making clear that the sheets are composed by aggregates of regular disk-like particles. The average size was estimated to be around 34 nm (Figure 5).…”

Section: Resultsmentioning

confidence: 91%

Quantum confinement in PbI2 nanodisks prepared with cucurbit[7]uril

Santos

Pereira

Demets

2011

J. Braz. Chem. Soc.

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Este trabalho apresenta uma rota alternativa para a preparação de nanodiscos de iodeto de chumbo (ca. 50-340 × 7Å, diâmetro × espessura) utilizando o macrocíclico cucurbit [7]urila como molde de síntese e agente estabilizante. Estas nanopartículas apresentam um deslocamento para o azul de gap óptico consistente com seu tamanho reduzido e confinamento quântico 1D. Suas espessuras são compatíveis com a de uma camada de iodeto de chumbo esfoliado, indicando que cucurbit [7]urila impede a formação de estruturas lamelares e limita o crescimento das nanopartículas. A estrutura, a morfologia e as propriedades destes discos foram verificadas por difratometria de raios X em pó (XRD), espectroscopia no UV-Visível, microscopia de força atômica (AFM), microscopia eletrônica de varredura com análise de fluorescência de raios X por dispersão de energia (SEM-EDS) e microscopia eletrônica de transmissão de alta resolução (HRTEM).This work presents an alternative route for the preparation of heavy metal iodide nanoparticles, particularly lead iodide nanodisks (ca. 50-340 × 7 Å, diameter × thickness), using the macrocycle cucurbit [7]uril as a synthetic template and stabilizing agent. These nanoparticles exhibit an opticalgap blue shift consistent with their small size and 1D quantum confinement. Their thicknesses are compatible with an exfoliated single layer of lead iodide, indicating that cucurbit [7]uril, preventing the stacking and formation of tactoids, thus limiting nanoparticles growth in the z direction. The structure, morphology and properties of these disks were analyzed by X-ray powder diffractometry (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), scanning electron microscopy with analysis of energy dispersive X-ray fluorescence (SEM-EDS) and high resolution transmission electron microscopy (HRTEM).Keywords: lead iodide, cucurbit [7]uril, synthetic template, nanodisks, quantum confinement IntroductionLead iodide is a lamellar solid consisting of layers of metal and iodide ions united by covalent bonds. Weak van der Waals interactions hold these layers together in a three dimensional sandwich-like semiconductor. This structure can be described as a hexagonal close-packed array of iodide anions with alternate layers of octahedral interstices occupied by lead(II) cations. Therefore, each layer can be described as a I-Pb-I sequence layer.1 Very interesting materials can be obtained by diminishing the PbI 2 particle size to the nanoscale in order to favor the appearance of new properties resultant of quantum confinement, such as those observed in zero-dimensional solids, quantum dots and other N-dimensional, quantumconfined nanomaterials. Quantum dots encounter many applications in several technological fields such as sensor devices and anti-counterfeiting systems, illumination (as high efficiency white-light emitting diodes), medicine (as cellular markers), lasers, solar cells and others.2-5 Another important property of lead iodide is its ability to form intercalation compounds with many chemical species, ...

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“…The solubility of CB[n]s in water also varies depending on the method used to synthesise and purify them; many CB[n]s precipitate from solution with co-crystallised acid molecules [21], which can be difficult to remove. Alkali earth metal salts also increase the solubility of CB[n]s, particularly saline [22][23][24][25][26][27]. In the latter case, the cations are strongly bound at the portals and can help stabilise the binding of small guests inside the cavity [22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Use of Cucurbit [6] Uril as a Modifier in the Electrochemical Determination of Antitumor Platinum (II) Complex: <i>Trans</i>-[PtCl<sub>2</sub>(Dimethylamine) (Isopropylamine)]. Application to Biological Samples

Domínguez¹,

Hernández²

2013

AJAC

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A square wave voltammetry (DPV) method for trans-Pt[Cl 2 (Dimethylamine)(isopropylamine)] determination is developed. To this end, all the chemical and instrumental variables affecting the determination of trans-Pt[Cl 2 (Dimethylamine) (isopropylamine)] are optimized. From studies of the mechanisms governing the electrochemical response of transPt[Cl 2 (Dimethylamine)(isopropylamine)], it was concluded that it was an electrochemically reversible system with an adsorptive oxidation phenomenon. Under optimal conditions, the variation of analytical signal (Ip) with transPt[Cl 2 (Dimethylamine)(isopropylamine)] concentration was linear in the 0.05 µg·mL -1 to 10 µg·mL -1 range, with a LOD 91 µg·mL -1 of and a LOQ of 303 µg·mL -1 , a RSD 1.10% and Er 0.72%. The optimized method was applied to the determination of trans-Pt[Cl 2 (Dimethylamine)(isopropylamine)] in biological fluids, in human urine and synthetic urine.

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Cucurbituril as a ligand for the complexation of cations in aqueous solutions

Cited by 156 publications

References 20 publications

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

Quantum confinement in PbI2 nanodisks prepared with cucurbit[7]uril

Use of Cucurbit [6] Uril as a Modifier in the Electrochemical Determination of Antitumor Platinum (II) Complex: <i>Trans</i>-[PtCl<sub>2</sub>(Dimethylamine) (Isopropylamine)]. Application to Biological Samples

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Cucurbituril as a ligand for the complexation of cations in aqueous solutions

Cited by 156 publications

References 20 publications

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

Quantum confinement in PbI2 nanodisks prepared with cucurbit[7]uril

Use of Cucurbit [6] Uril as a Modifier in the Electrochemical Determination of Antitumor Platinum (II) Complex: &lt;i&gt;Trans&lt;/i&gt;-[PtCl&lt;sub&gt;2&lt;/sub&gt;(Dimethylamine) (Isopropylamine)]. Application to Biological Samples

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Use of Cucurbit [6] Uril as a Modifier in the Electrochemical Determination of Antitumor Platinum (II) Complex: <i>Trans</i>-[PtCl<sub>2</sub>(Dimethylamine) (Isopropylamine)]. Application to Biological Samples