Foldamers are chain-like molecules that fold into a conformationally ordered state in solution. The design of foldamers can allow for a high degree of control over the folded molecular shape. Achieving shape changes through defined conformational dynamics is more challenging. As shown by some proteins, such dynamics can be key to molecular function.

Ivan Huc, Ludwig-Maximilians University, Munich, Germany, and colleagues have synthesized a foldamer designed to self-assemble in a multi-stranded aromatic sheet with a half-pipe-like shape, promoted by intermolecular H-bonding and the stacking of aromatic rings. The team used ion-mobility mass spectrometry and X-ray crystallography to confirm the formation of the desired foldamer. They also found an unexpected structural change between two distinct conformational dimeric states that require large changes to interconvert (pictured). In one conformer, the segments are flat and stacked perpendicular to the structure’s main axis, in the second, they are tilted and slightly twisted.

This structural change involves a complex and large-amplitude sliding of two subunits with respect to one another. This is an example of a new type of molecular motion, emerging from the increasingly large and complex molecules that are now accessible. The half-pipe shape of the dimer has potential applications in molecular recognition, as a synthetic channel, or in a molecular switch.

• Large‐Amplitude Conformational Changes in Self‐Assembled Multi‐Stranded Aromatic Sheets,
  Joan Atcher, Pedro Mateus, Brice Kauffmann, Frédéric Rosu, Victor Maurizot, Ivan Huc,
  Angew. Chem. Int. Ed. 2020.
  https://doi.org/10.1002/anie.202014670