Credit: © 2008 Wiley

The functions of nucleic acids and proteins are determined by the sequence of their constituent monomers — nucleotides and amino acids, respectively — and the way in which the resulting long chains fold to form different structures. Much research is focused on studying the sequence–structure–function relationship of such molecules by using synthetic versions — so-called foldamers — as models. There is increasing interest in going a step further, however, and creating extra functionality by synthesising foldamers in which the main chain — analogous to the sugar–phospate backbone in nucleic acids — contains variable components, rather than one repeated unit found in their natural counterparts.

Ivan Huc from Université Bordeaux 1 and colleagues from France and China have now developed1 a compound that contains five different types of aromatic units, based on pyridine or larger nitrogen heterocycles, linked together in a chain by amide bonds. A sequence in the centre of the foldamer causes it to twist into a helical structure, which creates a hollow large enough to house an alkyl chain. The pyridine groups in the foldamer are available to bind to hydroxyl or amine groups present in guest molecules, making alkane diols and alkane diamines ideal candidates. Molecules ranging in size from ethylene glycol to 1,4-butanediol were incorporated in the helical structures.

The foldamer's conformation can be adapted to the presence of a particular guest by varying the component monomers, such that longer molecules with different functional groups can be incorporated. The work could lead towards the elaboration of new, non-natural codes for sequence–structure–function relationships.