Assembly of p-selectin ligands on a polymeric template.

High-affinity receptor-ligand interactions frequently involve molecular interactions at two distinct sites. A derivatized polyacrylic-based polymer was synthesized to allow substitution with multiple ligands (e.g., L(1) and L(2)) on the backbone. Two-site P-selectin-ligand interactions were first studied with SiaLe(x) (L(1)) and tyrosine sulfate (L(2)) covalently incorporated onto the flexible polymer. In competition assays, a marked synergistic inhibitory effect was observed when the polymer presented both L(1) and L(2) as opposed to either ligand alone. In a second approach, the SiaLe(X) ligand was reduced in complexity so that L(1) was fixed as Le(x) or Le(a), and alternative L(2) groups (to mimic sialic acid) were investigated. Certain combinations of L(1) and L(2) were better antagonists of P-selectin than SiaLe(x) itself. These approaches offer the potential of facilitating the discovery of novel inhibitors of receptors or enzymes.