Self-assembled structures of nucleic acids, proteins and saccharides form the backbone of natural systems. Scientists have been able to engineer analogous, but simpler, self-assembly systems made of oligonucleotides and oligopeptides, but self-assembly of oligosaccharide has been hard to achieve. Now, Yu et al. show that certain oligosaccharides, ranging from dimers to hexamers, can form self-assembled nanostructures as well.
The researchers synthesize a series of oligosaccharides with different chemical modifications and length. They observe that structures bonding through a 1,4-glycosidic linkage do not self-assemble, because this kind of linkage limits the conformational degrees of freedom of the oligomer. Instead, 1,6-linked oligosaccharides can give rise to nanosized spheres and needles depending on the length and chemical modifications. Self-assembled structures arise due to the formation of an extended hydrogen bonding network. Contribution of π–π stacking is relevant only if certain organic solvents and certain sample preparation protocols are used. The fluorescence spectra of the oligosaccharides are also consistent with the formation of stacked structures.
Being able to design oligosaccharides with defined self-assembly behaviour adds to the toolkit of bio-inspired materials and sheds light on the intermolecular interactions among saccharides in natural systems.