Helical polysaccharides

In analogy to polypeptides and polynucleotides, polysaccharides tend to form helical secondary structures, as well as higher hierarchical assemblies. Nevertheless, the conformation of polysaccharides in solution remains in most cases elusive due to their intrinsic complexity and lack of analytical techniques. In this review, we discuss the different helical shapes adopted by polysaccharides, with particular focus on how the helical character is exploited to form supramolecular assemblies, such as inclusion complexes with linear guest molecules and co-helices with polynucleotide strands. Several methodologies are used to tune the polysaccharides conformation, ranging from ion-mediated coil-helix transition to chemical synthesis of well-defined compounds with specific modifications. The latter provides ideal tailor-made probes for structural studies, with the aim to correlate their three-dimensional structure and the macroscopic properties. Applications of oligosaccharides with defined shapes in molecular recognition and catalysis are envisioned.