posted on 2020-09-29, 15:12authored byRené
P. M. Lafleur, Svenja Herziger, Sandra M. C. Schoenmakers, Arthur D. A. Keizer, Jahaziel Jahzerah, Bala N. S. Thota, Lu Su, Paul H. H. Bomans, Nico A. J. M. Sommerdijk, Anja R. A. Palmans, Rainer Haag, Heiner Friedrich, Christoph Böttcher, E. W. Meijer
Supramolecular fibers
in water, micrometers long and several nanometers
in width, are among 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 were long thought to be chains of single
molecules stacked in one dimension (1D). Detailed cryogenic transmission
electron microscopy (cryo-TEM) studies and subsequent three-dimensional-volume
reconstructions unveiled helical repeats, ranging from 15 to 30 nm.
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, such
as 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.