Polymorphism in benzene-1,3,5-tricarboxamide supramolecular assemblies in water:a subtle trade-off between structure and dynamics

\u3cp\u3eIn biology, polymorphism is a well-known phenomenon by which a discrete biomacromolecule can adopt multiple specific conformations in response to its environment. The controlled incorporation of polymorphism into noncovalent aqueous assemblies of synthetic small molecules is an important step toward the development of bioinspired responsive materials. Herein, we report on a family of carboxylic acid functionalized water-soluble benzene-1,3,5-tricarboxamides (BTAs) that self-assemble in water to form one-dimensional fibers, membranes, and hollow nanotubes. Interestingly, one of the BTAs with the optimized position of the carboxylic group in the hydrophobic domain yields nanotubes that undergo reversible temperature-dependent dynamic reorganizations. SAXS and Cryo-TEM data show the formation of elongated, well-ordered nanotubes at elevated temperatures. At these temperatures, increased dynamics, as measured by hydrogen-deuterium exchange, provide enough flexibility to the system to form well-defined nanotube structures with apparently defect-free tube walls. Without this flexibility, the assemblies are frozen into a variety of structures that are very similar at the supramolecular level, but less defined at the mesoscopic level.\u3c/p\u3

Supramolecular Double Helices from Small C3-symmetrical Molecules Aggregated in Water

Supramolecular fibers in water, micrometers long and several nanometers in width, are amongst the most studied nanostructures for biomedical applications. These supramolecular polymers are formed through a spontaneous self-assembly process of small amphiphilic molecules by specific secondary interactions. Although many compounds do not possess a stereocenter, recent studies suggest the (co-)existence of helical structures, albeit in racemic form. Here, we disclose a series of supramolecular (co)polymers based on water-soluble benzene-1,3,5-tricarboxamides (BTAs) that form double helices, fibers that for long were thought to be chains of single molecules stacked in one dimension (1D). Detailed cryo-TEM studies and subsequent 3D-volume reconstructions unveiled helical repeats, ranging from 15-30 nanometer. Most remarkable, the pitch can be tuned through the composition of the copolymers, where two different monomers with the same core but different peripheries are mixed in various ratios. Like in lipid bilayers, the hydrophobic shielding in the aggregates of these disc-shaped molecules is proposed to be best obtained by dimer-formation promoting supramolecular double helices. It is anticipated that many of the supramolecular polymers in water will have a thermodynamic stable structure being such a double helix, although small structural changes can yield single stacks as well. Hence, it is essential to perform detailed analyses prior to sketching a molecular picture of these 1D fibers

Supramolecular Double Helices from Small C3Symmetrical Molecules Aggregated in Water

Supramolecular fibers in water, micrometers long and several nanometers in width, are amongst the most studied nanostructures for biomedical applications. These supramolecular polymers are formed through a spontaneous self-assembly process of small amphiphilic molecules by specific secondary interactions. Although many compounds do not possess a stereocenter, recent studies suggest the (co-)existence of helical structures, albeit in racemic form. Here, we disclose a series of supramolecular (co)polymers based on water-soluble benzene-1,3,5-tricarboxamides (BTAs) that form double helices, fibers that for long were thought to be chains of single molecules stacked in one dimension (1D). Detailed cryo-TEM studies and subsequent 3D-volume reconstructions unveiled helical repeats, ranging from 15-30 nanometer. Most remarkable, the pitch can be tuned through the composition of the copolymers, where two different monomers with the same core but different peripheries are mixed in various ratios. Like in lipid bilayers, the hydrophobic shielding in the aggregates of these disc-shaped molecules is proposed to be best obtained by dimer-formation promoting supramolecular double helices. It is anticipated that many of the supramolecular polymers in water will have a thermodynamic stable structure being such a double helix, although small structural changes can yield single stacks as well. Hence, it is essential to perform detailed analyses prior to sketching a molecular picture of these 1D fibers