Using small molecules to facilitate exchange of bicarbonate and chloride anions across liposomal membranes

Bicarbonate is involved in a wide range of biological processes, which include respiration, regulation of intracellular pH and fertilization. In this study we use a combination of NMR spectroscopy and ion-selective electrode techniques to show that the natural product prodigiosin, a tripyrrolic molecule produced by microorganisms such as Streptomyces and Serratia , facilitates chloride/bicarbonate exchange (antiport) across liposomal membranes. Higher concentrations of simple synthetic molecules based on a 4,6-dihydroxyisophthalamide core are also shown to facilitate this antiport process. Although it is well known that proteins regulate Cl − /HCO 3 − exchange in cells, these results suggest that small molecules may also be able to regulate the concentration of these anions in biological systems. The transport of bicarbonate anions across cell membranes by proteins is an important biological process, and if not regulated properly it can lead to cystic fibrosis and heart disease. Now, it has been shown that ‘small’ molecules can also promote efficient bicarbonate transport across lipid membranes and could be used to probe this process.