Fructose controlled ionophoric activity of a cholate–boronic acid

Abstract

Wulff-type boronic acids have been shown to act as ionophores at pH 8.2 by transporting Na(+) through phospholipid bilayers. A cholate-boronic acid conjugate was synthesised and shown to be an ionophore, although the hydroxyl-lined face of the cholate moiety did not enhance ion transport. Mechanistic studies suggested a carrier mechanism for Na(+) transport. The addition of fructose (>5 mM) strongly inhibited ionophoric activity of the cholate-boronic acid conjugate, mirrored by a strong decrease in the ability of this compound to partition into an organic phase. Modelling of the partitioning and ion transport data, using a fructose/boronic acid binding constant measured at pH 8.2, showed a good correlation with the extent of fructose/boronic acid complexation and suggested high polarity fructose/boronic acid complexes are poor ionophores. The sensitivity of ion transport to fructose implies that boronic acid-based antibiotic ionophores with activity modulated by polysaccharides in the surrounding environment may be accessible.

Ganglioside‐Selective Mechanosensitive Fluorescent Membrane Probes

“…Their recognition was envisioned with dynamic covalent bonds between boronic acids and diols ( Scheme ) . There is massive evidence for the power of dynamic covalent boronate esters in functional supramolecular systems in general, including fluorescent probes, sensors, bioorthogonal labeling, covalent organic frameworks, carriers, pores, photosystems, and so on. Sialic acid‐boronate interactions have been used before for cellular uptake …”