High Affinity Glycodendrimers for the Lectin LecB from Pseudomonas aeruginosa

Following an iterative oxime ligation procedure, cyclopeptide (R) and lysine-based dendron (D) were combined in all possible arrangements and successively functionalized with α-fucose and β-fucose to provide a new series of hexadecavalent glycosylated scaffolds (i.e., scaffolds RD₁₆, RR₁₆, DR₁₆, and DD₁₆). These compounds and smaller analogs (tetra- and hexavalent scaffolds R₄ and R₆) were used to evaluate the influence of the ligand valency and architecture, and of the anomer configuration in the binding to the αFuc-specific lectin LecB from Pseudomonas aeruginosa. Competitive enzyme-linked lectin assays (ELLA) revealed that only the RD₁₆ architecture displaying αFuc (<b>9A</b>) reaches strong binding improvement (IC₅₀ of 0.6 nM) over αMeFuc, and increases the α-selectivity of LecB. Dissociation constant of 28 nM was measured by isothermal titration micorcalorimetry (ITC) for <b>9A</b>, which represents the highest affinity ligand ever reported for LecB. ITC and molecular modeling suggested that the high affinity observed might be due to an aggregative chelate binding involving four sugar head groups and two lectins. Interestingly, unprecedented binding effects were observed with β-fucosylated conjugates, albeit being less active than the corresponding ligands of the αFuc series. In particular, the more flexible lysine-based dendritic structures (<b>15B</b> and <b>18B</b>) showed a slight inhibitory enhancement in comparison with those having cyclopeptide core