An artificial sodium ion channel from calix[4]arene in the 1,3-alternate conformation

Abstract

The synthesis of a calix[4]arene with pendent polyether substituents is described. The compound was shown by NMR to bind Na⁺ when in the 1,3-alternate conformation and computational simulations suggest metal binding within the calixarene annulus. ¹H NMR indicated that the complexed cation attracts water and the formation of a stable dihydrate was also indicated by in silico methods. Lipid bilayer experiments confirmed that the 1,3-alt calixarene functions as an artificial transmembrane ion in the presence of Na⁺ but not K⁺.

Keywords:

• calixarenes
• polyethers
• artificial ion channels
• electrophysiology
• ion transport

Acknowledgements

We thank the University of Brighton for financial support (for K.S.J.I. and F.F.).

Notes

^1. A similar bilayer experiment in Na⁺ rich media carried out using the crude mixture of cone compounds, including cone 4, also demonstrated insertion into the lipid membrane but no transmembrane ion current was observed [data not shown]. As the cone compounds are ca. 1.7 nm when fully extended it is probable that they are unable to span the bilayer and therefore cannot form conducting channels.