Highly Selective Artificial Cholesteryl Crown Ether K(+)-Channels.

The bacterial KcsA channel conducts K(+) cations at high rates while excluding Na(+) cations. Herein, we report an artificial ion-channel formed by H-bonded stacks of crown-ethers, where K(+) cation conduction is highly preferred to Na(+) cations. The macrocycles aligned along the central pore surround the K(+) cations in a similar manner to the water around the hydrated cation, compensating for the energetic cost of their dehydration. In contrast, the Na(+) cation does not fit the macrocyclic binding sites, so its dehydration is not completely compensated. The present highly K(+)-selective macrocyclic channel may be regarded as a biomimetic of the KcsA channel.