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This brief review highlights recent advances in the transport of oxoanions using synthetic carriers, focusing on both progress and ongoing challenges in the field. The difficulty of transporting these oxoanions increases with their hydration enthalpies, with less hydrated nitrate and perchlorate being relatively easy to transport. Recent progress has focused on the transport of moderately hydrated anions such as bicarbonate and carboxylates, where studies are influenced by the free diffusion of neutral species obtained by (de)protonation equilibria. Despite significant innovations in the design of synthetic carriers, the transport of the highly hydrated oxoanions sulfate and phosphate remains a major challenge. Progress on sulfate transport has stalled, while the first example of phosphate transport was reported only last year. [Display omitted] [ABSTRACT FROM AUTHOR]

Two tripodal squaramide conjugates having 4-(trifluoromethyl)phenyl and 3,5-bis(trifluoromethyl)phenyl substituents were synthesized and found to exhibit highly efficient transmembrane anion transport with the EC 50 values being 0.14 and 0.75 mol%, respectively. Though one of them has been reported to act as a strong anion receptor, in particular for sulfate anions, these two compounds exhibit no significant selectivity with respect to the tested monovalent anions and a very low level of activity in the presence of sulfate anions. [ABSTRACT FROM AUTHOR]

2,6-Bis(benzimidazol-2-yl)pyridine was shown to exhibit potent anionophoric activity via a process of both Cl − /NO 3 − antiport and H + /Cl − symport. This is in sharp contrast to the finding that its corresponding N -methylated analog exhibited negligible activity and reveals the importance of the imidazolyl-N H fragments in the anion-transport process. [ABSTRACT FROM AUTHOR]

A rigid bis(choloyl) conjugate functionalized with guanidino groups was synthesized and fully characterized on the basis of NMR ( 1 H and 13 C) and ESI MS (LR and HR) data. Its transmembrane ionophoric activity across egg-yolk l -α-phosphatidylcholine-based liposomal membranes was investigated by means of chloride ion selective electrode technique and pH discharge assay. The data indicate that under the assay conditions, this conjugate was capable of promoting the transport of anions, presumably via a cation/anion symport process. A Hill analysis reveals that two molecules of this compound are assembled into the transport-active species. [ABSTRACT FROM AUTHOR]

Prodiginines and tambjamines are anion-selective ionophores capable of facilitating the transport of anions across the plasma membrane in mammalian cells. One of the potential applications of these anionophores is the possibility of employing them as a substitutive therapy for pathologies involving anion channels, as in cystic fibrosis. We have studied the interaction of a large anion as gluconate with three prodiginine- and two tambjamine-like compounds. Apparent dissociation constants for the chloride, iodide and gluconate complexes were estimated from iodide influx experiments in mammalian cells exposed to different extracellular anion combinations. Our experiments indicate that gluconate is not transported by the prodiginines, leaving the anionophores free to transport chloride and iodide. Conversely, gluconate would be transported to some extent by the tambjamines, competing with halides for the anionophores, and consequently reducing their flux. This might be related to the different structural features of both families of compounds. These data have important implications for the selection of impermeable anions in the analysis of the anionophore mechanism. [ABSTRACT FROM AUTHOR]