title: Supramolecular selective transport of Ca2+/Na+ by dicarboxylic ligands across bulk liquid membranes.
abstract: Bulk liquid membrane transport of Ca2+ and Na+ ions was performed with dicarboxylic type ligands containing (S)-phenylalanine (Phe-2-O) and (S)-benzyltyrosine (Bz-Tyr-2-O) in pH gradients. With Bz-Tyr-2-O, calcium was generally favoured at every pH, the transport rate strongly depending upon the ligand concentration. At pH 8, a reversal of selectivity (Na+/Ca2+) was observed for the first time at low ligand concentration, thus suggesting that a supramolecular-type of transport occurs as a consequence of the different assemblages formed by the ligand according to pH and concentration. This is the first case of M2+/M+ selectivity induced by the carrier concentration.
authors.affiliation: Istituto di Chimica Organica, Università di Parma, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Biancardi
authors.forename: R
authors.initials: R
authors.lastname: Marchelli
authors.forename: A
authors.initials: A
authors.lastname: Dossena
mesh_terms: D001667:Binding, Competitive; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D003998:Dicarboxylic Acids / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008567:Membranes, Artificial; D012964:Sodium / Q000378:metabolism*
chemical_list: D003998:Dicarboxylic Acids; D008024:Ligands; D008567:Membranes, Artificial; D012964:Sodium; D002118:Calcium