Y. Nakatsuji et al., DOUBLE UPHILL TRANSPORT OF CA2-NA+ OR CA2+-K+ IN OPPOSITE DIRECTIONS BY LIPOPHILIC CROWN-ETHERS WITH 2 CARBOXYLIC-ACID MOIETIES(), Journal of organic chemistry, 62(18), 1997, pp. 6231-6235
A variety of lipophilic crown ethers containing two carboxylic acid mo
ieties were prepared, and their transport abilities were estimated in
the double uphill transport system of Ca2+-Na+ or Ca2+-K+ by pH contro
l through a bulk liquid membrane using dichloromethane. As expected, 1
5-crown-5 and 18-crown-6 derivatives were found to be effective for Ca
2+-Na+ and Ca2+-K+ exchange systems, respectively. As a result, the ca
lcium ion was concentrated in the acidic phase, and the sodium ion or
potassium ion was concentrated in the other phase. In addition to the
structure of the carriers, a proper selection of the transport conditi
ons was one of the crucial factors for realizing this double uphill tr
ansport system. A simple combination of the active transporter of the
calcium ion and the passive carrier for the sodium ion was also found
to enable the exchange between the calcium and sodium ions against the
ir concentration gradients. When two ionophores effective for Ca2+-Kand K+-Na+ exchange systems, respectively, were used at the same time,
the calcium and potassium ions were concentrated in the acidic phase,
whereas the sodium ion was concentrated in the basic phase.