Biancardi A, Marchelli R, Dossena A. Supramolecular selective transport of Ca2+/Na+ by dicarboxylic ligands across bulk liquid membranes.
J Mol Recognit 1992;
5:139-44. [PMID:
1339482 DOI:
10.1002/jmr.300050404]
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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.
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