Angew. Chem. Int. Ed. 56, 1329–1333 (2017)

Biochemical transformations involve a local exchange of energy that affords natural systems with their unique ability to adapt to environmental conditions. Biological assemblies, for example, are often transient species that can perform a specific function. Their transient character results from the complex interplay of biochemical reactions that promote and suppress their formation. Recreating transient assemblies in artificial supramolecular systems can be useful to fabricate adaptive materials that can respond in a spatially and temporally controlled manner to environmental changes. Dhiman et al. now describe a supramolecular assembly that can temporarily switch its chirality.

The system comprises a naphthalene diimide molecule functionalized with a phosphate receptor group that self-assembles in a helical stack in response to binding with either ATP or ADP molecules. Notably, ATP drives the formation of P-helices, whereas ADP drives the formation of M-helices. Dhiman et al. take two enzymes, one that generates and one that consumes ATP through different pathways. Starting with the substrate that produces ADP, they observe the formation of an M-helical stack. Subsequent addition of the substrate that generates ATP triggers the conformational switch to a P-stack, as ADP-bound molecules are converted into ATP by the first enzyme. At this point, the presence of a high concentration of ATP activates the second enzyme, reverting the helicity of the stack. By changing various parameters, Dhiman et al. can program the lifetime of the transient species.