The transport of ions across membranes is crucial for many biological processes, including signal transduction, ATP synthesis, and homeostasis. Ions are not able to cross the apolar interior of lipid bilayers spontaneously, thus membrane proteins take care of the transport of ions in biology. Absence or malfunction of such membrane proteins acting as ion channels is the cause of several diseases, including cystic fibrosis. Synthetic compounds can also be used to transport ions across membranes. Such compounds can act as mobile carriers by extracting the ion from the aqueous phase, move it across the apolar interior of the lipid bilayer, to then release it on the other side of the membrane. Numerous synthetic ion transporters have been developed over the past two decades and some were found to have promising biological activity.[1] In our lab in Brussels, we are developing synthetic receptors for the transmembrane transport of anions and cations. In addition to the development of selective transporters for Cl,[2] we are exploring transport of HCO3,[3] F,[4] and H2PO4,[5] anions that are biologically relevant but more difficult to transport due their geometry, hydration, and different (de)protonation equilibria. I will show that transporters for such anions require increasingly intricate molecular designs.
Our efforts in the field of cation transport mainly focus on the transport of copper. We have recently reported the first synthetic Cu+ transporter, based on a calix[4]arene with two imidazole groups.[6] Biological studies on these compounds by collaborators (in particular at the Université Grenoble Alpes) have demonstrated their activity in cells and their potent anticancer effects.

​Funding
​ • Fonds de la Recherche Scientifique – FNRS
• ERC, Starting Grant ORGANITRA (802727)

References
[1] A. Roy, P. Talukdar, ChemBioChem 2021, 22, 2925–2940.
[2] A. Singh, A. Torres-Huerta, T. Vanderlinden, N. Renier, L. Martínez-Crespo, N. Tumanov, J. Wouters, K. Bartik, I. Jabin, H. Valkenier, Chem. Commun. 2022, 58, 6255–6258.
[3] L. Martínez‐Crespo, S. H. Hewitt, N. A. D. Simone, V. Šindelář, A. P. Davis, S. Butler, H. Valkenier, Chem. Eur. J. 2021, 27, 7367–7375.X. Wu, A. M. Gilchrist and P. A. Gale, Chem, 2020, 6, 1296–1309.
[4] A. Cataldo, M. Chvojka, G. Park, V. Šindelář, F. P. Gabbaï, S. J. Butler, H. Valkenier, Chem. Commun. 2023, 59, 4185–4188.
[5] A. Cataldo, K. Norvaisa, L. Halgreen, S. E. Bodman, K. Bartik, S. J. Butler, H. Valkenier, J. Am. Chem. Soc. 2023, 145, 16310–16314.
[6] N. Renier, O. Reinaud, I. Jabin, H. Valkenier, Chem. Commun. 2020, 56, 8206–8209.
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