Rigid-rod molecules in biomembrane models: from hydrogen-bonded chains to synthetic multifunctional pores.

Synthetic ion channels and pores formed by rigid-rod molecules are summarized. This includes work on hydrogen-bonded chains installed along membrane-spanning rigid-rod scaffolds to transport protons. As a second topic, programmed assembly of p-septiphenyls with terminal iminodiacetate-copper complexes for potassium transport by cation-pi interactions is described. The third topic concerns rigid push-pull rods as fluorescent alpha-helix mimics to probe the importance of dipole-potential interactions for voltage gating, both on the functional and the structural level. Topic number four deals with p-octiphenyl staves as key scaffolds for the synthesis of rigid-rod beta-barrel pores. The description of internal and external design strategies for these rigid-rod beta-barrels covers a rich collection of pH-, pM-, voltage-, ligand-, and enzyme-gated synthetic multifunctional pores that can act as hosts, sensors, and catalysts. As far as practical applications are concerned, the possibility to detect chemical reactions with synthetic multifunctional pores appears most attractive. Recent molecular mechanics simulations are presented as a valuable approach to insights on the elusive suprastructures of multifunctional pores made from rigid rods.