1.D.224.  The Biotin[6]Uril Hexaacid Anion Carrier (BUH-AC) Family 

Biotin[6]uril hexaacid  forms anion-selective channels in water by employing non-polarizable and polarizable force fields (Seiferth et al. 2023). Anion binding shows strong solvent dependency, consistent with experimental studies. In water, the binding strengths are iodide > bromide > chloride, (and reversed in acetonitrile). These trends are well captured by both classes of force fields. However, the free energy profiles obtained from potential of mean force calculations and preferred binding positions of anions depend on the treatment of electrostatics. Results from simulations using the AMOEBA force-field, which recapitulates the observed binding positions, suggest strong effects from multipoles dominate with a smaller contribution from polarization. The oxidation status of the macrocycle was also found to influence anion recognition in water. Overall, these results have implications for the understanding of anion host interactions not just in synthetic ionophores, but also in narrow cavities of biological ion channels (Seiferth et al. 2023).

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