Electrostatic and Allosteric Cooperativity in Ion-Pair Binding: A Quantitative and Coupled Experiment-Theory Study with Aryl-Triazole-Ether Macrocycles.
Cooperative binding of ion pairs to receptors is crucial for the manipulation of salts, but a comprehensive understanding of cooperativity has been elusive. To this end, we combine experiment and theory to quantify ion-pair binding and to separate allostery from electrostatics to understand their re...
| Publicado en: | Journal of the American Chemical Society Vol. 137; no. 30; pp. 9746 - 9758 |
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| Autores principales: | , , , , , , , |
| Formato: | Artículo |
| Publicado: |
American Chemical Society
8/5/2015
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=108979694&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 108979694 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 8/5/2015 vid: 137 iid: 30 pid: 997 pub: American Chemical Society artinfo: ui: 108979694 10.1021/jacs.5b05839 ppf: 9746 ppct: 12 formats: tig: atl: Electrostatic and Allosteric Cooperativity in Ion-Pair Binding: A Quantitative and Coupled Experiment-Theory Study with Aryl-Triazole-Ether Macrocycles. aug: au: Bo Qiao Sengupta, Arkajyoti Yun Liu McDonald, Kevin P. Pink, Maren Anderson, Joseph R. Raghavachari, Krishnan Flood, Amar H. affil: Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States su: Allosteric regulation Ion pairs Physiological control systems Density functional theory Ions sug: subj: Allosteric regulation Ion pairs Physiological control systems Density functional theory Ions ab: Cooperative binding of ion pairs to receptors is crucial for the manipulation of salts, but a comprehensive understanding of cooperativity has been elusive. To this end, we combine experiment and theory to quantify ion-pair binding and to separate allostery from electrostatics to understand their relative contributions. We designed aryl-triazole-ether macrocycles (MC) to be semiflexible, which allows ion pairs (NaX; X = anion) to make contact, and to be monocyclic to simplify analyses. A multiequilibrium model allows us to quantify, for the first time, the experimental cooperativity, α, for the equilibrium MC·Na + MC·X ⇄ MC·NaX + MC, which is associated with contact ion-pair binding of NaI (α = 1300, ΔG = -18 kJ mol) and NaClO (α = 400, ΔG = -15 kJ mol) in 4:1 dichloromethane-acetonitrile. We used accurate energies from density functional theory to deconvolute how the electrostatic effects and the allosteric changes in receptor geometry individually contribute to cooperativity. Computations, using a continuum solvation model (dichloromethane), show that allostery contributes ~30% to overall positive cooperativity. The calculated trend of electrostatic cooperativity using pairs of spherical ions (NaCl > NaBr > NaI) correlates to experimental observations (NaI > NaClO). We show that intrinsic ionic size, which dictates charge separation distance in contact ion pairs, controls electrostatic cooperativity. This finding supports the design principle that semiflexible receptors can facilitate optimal electrostatic cooperativity. While Coulomb's law predicts the size-dependent trend, it overestimates electrostatic cooperativity; we suggest that binding of the individual anion and cation to their respective binding sites dilutes their effective charge. This comprehensive understanding is critical for rational designs of ion-pair receptors for the manipulation of salts. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2015 holdings: @attributes: islocal: N |
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