Transmembrane Transport of Bicarbonate Unravelled** |
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Authors: | Dr Luis Martínez-Crespo Dr Sarah H Hewitt Dr Nicola Alessandro De Simone Prof Vladimír Šindelář Prof Anthony P Davis Dr Stephen Butler Dr Hennie Valkenier |
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Institution: | 1. Université Libre de Bruxelles (ULB), Engineering of Molecular NanoSystems, Ecole polytechnique de Bruxelles, Avenue F.D. Roosevelt 50, CP165/64, 1050 Brussels, Belgium;2. Loughborough University, Department of Chemistry, Epinal Way, Loughborough, LE11 3TU UK;3. Masaryk University, Department of Chemistry and RECETOX, Faculty of Science, Kamenice 5, 625 00 Brno, Czech Republic;4. University of Bristol, School of Chemistry, Cantock's Close, Bristol, BS8 1TS UK |
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Abstract: | Anion receptors can be used to transport ions across lipid bilayers, which has potential for therapeutic applications. Synthetic bicarbonate transporters are of particular interest, as defects in transmembrane transport of bicarbonate are associated with various diseases. However, no convenient method exists to directly observe bicarbonate transport and study the mechanisms involved. Here, an assay is presented that allows the kinetics of bicarbonate transport into liposomes to be monitored directly and with great sensitivity. The assay utilises an encapsulated europium(III) complex, which exhibits a large increase in emission intensity upon binding bicarbonate. Mechanisms involving CO2 diffusion and the dissipation of a pH gradient are shown to be able to lead to an increase in bicarbonate concentration within liposomes, without transport of the anion occurring at all. By distinguishing these alternative mechanisms from actual bicarbonate transport, this assay will inform the future development of bicarbonate transporters. |
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Keywords: | bicarbonate fluorescent probes ion transport membranes supramolecular chemistry |
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