Facilitated Transport of Hydrophilic Salts by Mixtures of Anion and Cation Carriers and by Ditopic Receptors

Anion transfer to the membrane phase affects the extraction efficiency of salt transport by cation carriers 1 and 3. Addition of anion receptors 5 or 6 to cation carriers 1, 3, or 3 in the membrane phase enhances the transport of salts under conditions in which the cation carriers alone do not transport salt. The extraction of salt by the carrier mixtures is larger than by cation or anion carrier only, but the rate of diffusion is lower. Ditopic receptors 8 and 9 transport CsCl or KCl much faster than monotopic anion receptor 7 or cation receptors 1 and 2. The faster transport is due to a higher extraction constant K-ex despite a lower diffusion constant of the ditopic salt complex.