Picking on Carbonate: Kinetic Selectivity in the Encapsulation of Anions

Abstract

Supramolecular hosts bind to inorganic anions at a fast rate and select them in proportion with thermodynamic stability of the corresponding [anion�host] complexes, forming in a reversible manner. In this study, we describe the action of hexapodal capsule 1 and its remarkable ability to select anions based on a large span of rates by which they enter this host. The thermodynamic affinity of 1 toward eighteen anions extends over eight orders of magnitude (0 < K a < 10 8 M À 1 ; 1 H NMR spectroscopy). The capsule would retain CO 3 2À (K a = 10 7 M À 1 ) for hours in the presence of eleven competing anions, including stronger binding SO 4 2À , HAsO 4 2À and HPO 4 2À (K a = 10 7 -10 8 M À 1 ). The observed selection resulted from 1 possessing narrow apertures (ca. 3 × 6 Å) comparable in size to anions (d = 3.5-7.1 Å) slowing down the encapsulation to last from seconds to days. The unorthodox mode of action of 1 sets the stage for creating hosts that pick anions by their ability to access the host.

Tertiary Plasticity Drives the Efficiency of Enterocin 7B Interactions with Lipid Membranes

“…ASMD has been previously benchmarked on neuropeptide Y and its mutants, deca-alanine in vacuum, implicit and explicit solvents, ,, and β-hairpin. , It has also been utilized successfully by several groups to investigate a large number of biophysical phenomena, such as mutagenesis, , host–guest interactions, protein–ligand interactions, and dissociation mechanisms …”