Fluorescence Visualization of Helix Inversion in Biomimic Polymeric Foldamer

Biomacromolecules such as DNA, proteins, and polysaccharides possess unique helical structures that are closely related to their biological functions involving recognition, catalysis, replication, and genetic information storage. From a biomimetic perspective, artificial foldamers are the ideal systems to model and study the structure-property relationship of biomacromolecules. Herein, we report a facile, rapid, and cost-effective method to directly visualize and monitor the solvent-driven helix inversion in a water-soluble poly(m-phenylene ethynylene)-based foldamer with the aid of a tetraphenylethene-functionalized hemicyanine dye. By adjusting the solvent environment, the foldamer transitions from an M-helix to a P-helix, accompanied by a change in the dye's binding mode from groove to surface. This transition alters the degree of restriction and microenvironment polarity, resulting in a visible emission color change from yellow to red, signaling the helix inversion. The present investigation offers a powerful tool for understanding conformational transitions in biomacromolecules and offers insights into the dynamic behavior of helical structures.