Synthesis of Bipyridine Carbohydrate Receptors
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Macrocyclic molecules consisting of aromatic groups with amino side chains are known to bind selectively to carbohydrates, mainly monosaccharides and oligosaccharides. Some of these macrocyclic molecules, for example, Pyridine-based and Naphthyridine-based macrocyclic structures, behave like carbohydrate receptors and bind selectively to carbohydrates in aqueous solutions through hydrogen bonding, hydrophobic and electrostatic interactions. Bipyridine receptors mimic natural lectins. A bipyridine receptor was designed and synthesized from Tris(2-aminoethyl)amine and 2,2-bipyridine-4,4-dicarboxyaldehyde. The receptor was purified and characterized using extraction, HPLC (High Performance Liquid Chromatography), NMR (Nuclear Magnetic Resonance) spectroscopy and ESI-MS (Electrospray Ionization Mass Spectrometry). Masses and peaks obtained matched the expected structure which was synthesized. The binding constants between the bipyridine receptor and six selected sugars in water were determined by UV-Vis (Ultraviolet Visible) spectroscopy titration. Studies confirmed that the bipyridine receptor was able to bind to three of the sugars. The observed dissociation constant values ranged from 0.16mM to 0.37mM. These values compared favorably with the reported binding constants between a 1,8-naphthyridine receptor and monosaccharide complexes, as well reported lectin/monosaccharide complexes in nature. The divalent version of the bipyridine receptor, which was expected to have better binding properties towards sugar substrates, was also prepared using solid phase synthesis. Two of the sugars that were able to bind to the bipyridine receptor occurred in high concentration in certain cancer tumor tissues. It is expected that the bipyridine receptor and the findings in this research can serve as source of information for further research work into early detection and treatment of cancer or other cellular communications in which glycoconjugates are important.