A threading receptor for polysaccharides

• Published in: Nature chemistry 2016-01, Vol.8 (1), p.69-74
• Main Authors: Mooibroek, Tiddo J., Casas-Solvas, Juan M., Harniman, Robert L., Renney, Charles M., Carter, Tom S., Crump, Matthew P., Davis, Anthony P.
• Format: Article
• Language: English
• Subjects: 140/131; 147/3; 639/638/455; 639/638/541; Analytical Chemistry; Aqueous solutions; Atomic force microscopy; Biochemistry; Biocompatible Materials - chemical synthesis; Biocompatible Materials - chemistry; Biological activity; Cellulose; Cellulose - chemistry; Chemistry; Chemistry/Food Science; Chitin; Chitin - chemistry; Chitosan; Circular dichroism; Dichroism; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Inorganic Chemistry; Microscopy, Atomic Force; Models, Molecular; Molecular Structure; Natural polymers; Organic Chemistry; Overhauser effect; Physical Chemistry; Polymers; Polysaccharides; Polysaccharides - chemistry; Receptors; Receptors, Artificial - chemical synthesis; Receptors, Artificial - chemistry; Saccharides; Solubility; Solubilization; Spectroscopy; Thermodynamics
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/nchem.2395

Cellulose, chitin and related polysaccharides are key renewable sources of organic molecules and materials. However, poor solubility tends to hamper their exploitation. Synthetic receptors could aid dissolution provided they are capable of cooperative action, for example by multiple threading on a single polysaccharide molecule. Here we report a synthetic receptor designed to form threaded complexes (polypseudorotaxanes) with these natural polymers. The receptor binds fragments of the polysaccharides in aqueous solution with high affinities ( K a up to 19,000 M −1 ), and is shown—by nuclear Overhauser effect spectroscopy—to adopt the threading geometry. Evidence from induced circular dichroism and atomic force microscopy implies that the receptor also forms polypseudorotaxanes with cellulose and its polycationic analogue chitosan. The results hold promise for polysaccharide solubilization under mild conditions, as well as for new approaches to the design of biologically active molecules. A synthetic receptor has been designed to form pseudorotaxanes and polypseudorotaxanes with oligo/polysaccharides in water. Target substrates have all-equatorial substitution patterns, and include cellulose, cellodextrins and the cationic polysaccharide chitosan. The results suggest an approach to dissolving these polysaccharides under mild conditions and could prove useful for processing these abundant renewable resources.