Macromolecular recognition: Effect of multivalency in the inhibition of binding of yeast mannan to concanavalin A and pea lectins by mannosylated dendrimers

Abstract

The synthesis and binding properties of a new family of high affinity α- d-mannopyranoside ligands are described. The synthesis of the new multivalent ligands is based on the scaffolding of multiantennary branches of l-lysine residues having electrophilic N-chloroacetylated end groups as core structures. An α- d-mannopyranoside with p-substituted aryl aglycon ending with a thiol group was prepared and covalently attached to each of the branches of the dendritic structures. The resulting glycodendrimers with 2 ( 12), 4 ( 14), 8 ( 16), and 16 ( 18) mannoside residues were tested for their relative inhibitory potency by solid-phase enzyme-linked lectin assays (ELLA) using methyl and p-nitrophenyl α- d-mannopyranosides as standards. Concentrations necessary for 50% inhibition (IC 50s) of binding of yeast mannan to Jack bean phytohemagglutinin ( Canavalia ensiformis, concanavalin A) and to pea lectin ( Pisum sativum) were determined. Analogous mannosylated copolyacrylamides were also prepared for comparison. The IC 50 values were also plotted as a function of dendrimer valencies. The inhibitions showed 16-mer 18 to be approximately 600- and 2000-fold more potent than methyl α- d-mannopyranoside, and 66- and 1383-fold more potent than p-nitrophenyl α- d-mannopyranosides with Con A and pea lectins, respectively. Even when these numbers are expressed relative to single mannopyranoside residues per dendrimers, the relative potencies against the aromatic mannoside are still 4- and 86-fold better against Con A and pea lectins. These results unequivocally indicate that the optimum inhibitory binding properties of the new mannosylated dendrimers vary with both dendrimer and lectin valencies.