Mechanism of Saccharide Separation Using The Ligand Exchange Mode

Saccharides exhibits an energy-stable chair conformation in 5-membered ring (furanose) or 6-membered ring (pyranose) forms. Since hydroxyl group on each carbon can take either equatorial or axial position, even two saccharides having the same molecular structures may have different three dimensional configurations. Ligand exchange mode separates saccharides using this configuration difference of the complex formed between saccharides' hydroxyl groups and metal ions. As shown in the left figure, saccharides having a larger number of ax-eq-ax configuration (triplet) units form stronger complexes with metal ions. Meanwhile, as right figure shows, saccharides lacking such a triplet structure form complexes with ax-eq (pair) hydroxyl group. As the unit number of this pair structure increases, saccharides become more potent forming complexes with metal ions. The complex formation capacity also differs depending on modified metal ions.