Binding Selectivity of Macrocycle Ionophores in Ionic Liquids versus Aqueous Solution and Solvent‐free Conditions

Gámez, Francisco; Hortal, Ana R.; Hurtado, Paola; Avilés–Moreno, Juan Ramón; Hamad, Said; Martínez–Haya, Bruno

doi:10.1002/cphc.201500477

Cited by 5 publications

(1 citation statement)

References 41 publications

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“…It has been reported that metal cations can assist host/guest interactions − and interact with CDs. , In a similar way, cationic bolaform heads are expected to interact with α-CD. The axle/CD complex should be considered as a transient along the reaction pathway for [2]pseudorotaxane formation.…”

Section: Resultsmentioning

confidence: 92%

Kinetic Study of [2]Pseudorotaxane Formation with an Asymmetrical Thread

et al. 2016

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Kinetic and thermodynamic studies on cyclodextrin (CD)-based [2]pseudorotaxane formation have been carried out by a combination of NMR and calorimetric techniques using bolaform surfactants as axles. Experimental evidence of the formation of an external complex between the trimethylammonium head groups of the axle and the external hydrogen atoms of α-cyclodextrin (α-CD) is reported. Inclusion of this external complex in the reaction pathway allows us to explain the kinetic behavior as well as the nonlinear dependence of the observed rate constant on CD concentrations. The equilibrium constant for [2]pseudorotaxane formation is strongly affected by the spacer length of the axle. This effect is a consequence of increasing rotaxane stability because the threading rate constant is almost independent of the spacer length, but dethreading strongly decreases on increasing the axle size. Using a nonsymmetrical axle with tripropyl and trimethylammonium cations precludes CD threading by the large head side. CDs will thread this asymmetrical bolaform by both their wide and narrow sides, yielding two isomeric [2]pseudorotaxanes. Threading by the wide side of the CD is 60% more favorable than that by the narrow one, but dethreading rate constants are the same for both isomers.

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Section: Resultsmentioning

confidence: 92%

Kinetic Study of [2]Pseudorotaxane Formation with an Asymmetrical Thread

et al. 2016

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Enhanced cation recognition by a macrocyclic ionophore at the air–solution interface probed by mass spectrometry

Rodrigo

Gámez

Avilés–Moreno

et al. 2016

Phys. Chem. Chem. Phys.

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Interfacial environments have the potential to drive unexpected events of supramolecular recognition, leading to advances in the development of novel functional materials and molecular sensing techniques. We present experimental evidence for a noticeable enhancement of the cation binding specificity of a prototype calixarene macrocycle (cesium ionophore II) at the air-solution interface, in comparison to bulk solution and to isolated solvent-less conditions. A rationalization of this intriguing finding is outlined, with the support of quantum calculations, in terms of the 'half-solvation' conditions provided by the interface and of conformational effects posed by the backbone structure and the side chains of the macrocyclic ionophore. The investigation involves the introduction of a mass spectrometry method to determine the relative abundances of interfacial complexes that should be of general application in the field and guide future advances in analytical techniques based on molecular recognition.

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Correlating the potentiometric selectivity of cyclosporin-based electrodes with binding patterns obtained from electrospray ionization-mass spectrometry

Zahran

Paeng

Badr

et al. 2017

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Electrospray ionization mass spectrometry ESI-MS is a powerful technique for the characterization of macromolecules and their noncovalent binding with guest ions. We herein evaluate the feasibility of using ESI-MS as a screening tool for predicting potentiometric selectivities of ionophores. Ion-selective electrodes based on the cyclic peptide, cyclosporin A, were developed, and their potentiometric selectivity pattern was evaluated. Optimized electrodes demonstrated near-Nernstian slopes with micromolar detection limits toward calcium. ESI-MS and ESI-MS/MS were employed to determine the relative association strengths of cyclosporin A with various cations. The observed MS intensities of ion-ionophore complexes correlate favorably with the potentiometric selectivity pattern that was demonstrated by cyclosporin-based electrodes. This correlation was found to hold true for other established ionophores, such as valinomycin and benzo-18-crown-6. Taken together, these experiments demonstrate that mass spectrometry could be used to predict the selectivity patterns of new ionophores for potentiometric and optical ion sensors. Further, this approach could be useful in screening mixtures or libraries of newly-synthesized compounds to identify selective ionophores.

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Binding Selectivity of Macrocycle Ionophores in Ionic Liquids versus Aqueous Solution and Solvent‐free Conditions

Cited by 5 publications

References 41 publications

Kinetic Study of [2]Pseudorotaxane Formation with an Asymmetrical Thread

Kinetic Study of [2]Pseudorotaxane Formation with an Asymmetrical Thread

Enhanced cation recognition by a macrocyclic ionophore at the air–solution interface probed by mass spectrometry

Correlating the potentiometric selectivity of cyclosporin-based electrodes with binding patterns obtained from electrospray ionization-mass spectrometry

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