Supramolecular assembly and chirality of synthetic carbohydrate materials

07 September 2020
Nous venons de publier les résultats de notre collaboration internationale avec MPI-Potsdam (Allemagne) dans Angewandte Chemie International Edition. Dans ce travail, nous avons construit un modèle de système de matériau glucidique basé sur des disaccahrdes de gluycose synthétique. L'analyse par diffraction électronique microcristalline (microED) a révélé que les disaccharides synthétiques formaient une fibre hélicoïdale hautement cristalline. La chiralité des fibres hélicoïdales assemblées peut être ajustée en modifiant la structure énantiomérique des disaccharides, soulignant le potentiel des matériaux glucidiques de concepteur pour les applications nanotechnologiques.

« Hierarchical carbohydrate architectures serve multiple
roles in Nature. Hardly any correlations between the carbohydrate
chemical structures and the material properties are available due to
the lack of standards and suitable analytic techniques. Therefore,
designer carbohydrate materials remain highly unexplored, as
compared to peptides and nucleic acids. Here, a synthetic D-glucose
disaccharide, DD, is chosen as model to explore carbohydrate
materials. Microcrystal electron diffraction (MicroED), optimized for
oligosaccharides, revealed that DD assemble into highly crystalline
left-handed helical fibers. The supramolecular architecture was
correlated to the local crystal organization, allowing for the design of
the enantiomeric right-handed fibers, based on the L-glucose
disaccharide, LL, or flat lamellas, based on the racemic mixture.
Tunable morphologies and mechanical properties suggest the
potential of carbohydrate materials for nanotechnology applications.
Carbohydrates, the most abundant organic material on Earth, are
also capable of forming hierarchical architectures. Still, their
molecular level description remains limited due to difficult access
to pure materials and a lack of suitable analytical techniques.
The potential of carbohydrate materials remains thus highly
underexploited. The synthesis of well-defined polysaccharide
sequences is labor intensive. Moreover, the intrinsic flexibility of
short oligosaccharides has hampered their use for the formation
of supramolecular structures. As a consequence, carbohydrates
have found limited applications in nanotechnology, with the only
exception being nanocellulose. Still, nanocellulose is often
directly extracted from natural sources (top-down approach),
limiting molecular design opportunities and detailed structurefunction
correlations. »

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