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Homotropic Allosterism: In-Depth Structural Analysis of the Gas-Phase Noncovalent Complexes Associating a Double-Cavity Cucurbit[n]uril-Type Host and Size-Selected Protonated Amino Compounds

Authors

  • Dr. Vincent Lemaur,

    1. Laboratory for Chemistry of Novel Materials, University of Mons, UMONS, 23 Place du Parc, 7000 Mons (Belgium)
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  • Glenn Carroy,

    1. Mass Spectrometry Research Group, Interdisciplinary Center for Mass Spectrometry (CISMa), University of Mons, UMONS, 23 Place du Parc, 7000 Mons (Belgium)
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  • Frédéric Poussigue,

    1. Université de Lyon, ISA, UMR 5280 Université Lyon 1-CNRS, 69622 Villeurbanne (France)
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  • Dr. Fabien Chirot,

    1. Université de Lyon, ISA, UMR 5280 Université Lyon 1-CNRS, 69622 Villeurbanne (France)
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  • Dr. Julien De Winter,

    1. Mass Spectrometry Research Group, Interdisciplinary Center for Mass Spectrometry (CISMa), University of Mons, UMONS, 23 Place du Parc, 7000 Mons (Belgium)
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  • Prof. Lyle Isaacs,

    1. Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742 (USA)
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  • Dr. Philippe Dugourd,

    1. Université de Lyon, ISA, UMR 5280 Université Lyon 1-CNRS, 69622 Villeurbanne (France)
    2. Université de Lyon, ILM, UMR 5306 Université Lyon 1-CNRS, 69622 Villeurbanne (France)
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  • Dr. Jérôme Cornil,

    1. Laboratory for Chemistry of Novel Materials, University of Mons, UMONS, 23 Place du Parc, 7000 Mons (Belgium)
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  • Prof. Pascal Gerbaux

    Corresponding author
    1. Mass Spectrometry Research Group, Interdisciplinary Center for Mass Spectrometry (CISMa), University of Mons, UMONS, 23 Place du Parc, 7000 Mons (Belgium)
    • Mass Spectrometry Research Group, Interdisciplinary Center for Mass Spectrometry (CISMa), University of Mons, UMONS, 23 Place du Parc, 7000 Mons (Belgium)
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Abstract

Noncovalent interactions between several protonated amines and an original ditopic receptor, nor-seco-cucurbit[10]uril, are investigated by combining mass spectrometry-based methods and computational chemistry. Electrospray ionization is used to transfer the intact supramolecular assemblies from their acidic solution to the gas phase, provided fine-tuning of the source parameters is achieved. Ternary complexes, associating two guest molecules and one host cavity, are observed systematically in the mass spectrometry analyses and the quasi-exclusive occurrence of these 2:1 associations reveals the allosteric nature of the complexation reaction. It is demonstrated that the binary 1:1 complex ions that are detected arise from collision-induced dissociation processes undergone by the ternary complex ions inside the ion source. Based on ion mobility experiments supported by theoretical calculations, the inclusion nature of the gas-phase ternary complexes is clearly evidenced independent of the size of the probed guest molecule and the charge state of the complex ions. The allosteric nature of the complexation reactions is dictated by size criteria. This is demonstrated on the basis of mass spectrometry experiments by analyzing solutions containing ligands of different sizes in competition for inclusion within the guest cavity. Computational chemistry is also used to characterize the three-dimensional structures of the complexes.

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