Protein-directed immobilization of phosphocholine ligands on a gold surface for multivalent C-reactive protein binding.

The preparation of a synthetic receptor for multivalent protein binding by a directed immobilization of bifunctional ligands was demonstrated using pentameric C-reactive protein (CRP) and a thiolated phosphocholine-containing ligand on a gold surface. CRP consisting of five identical, noncovalently linked subunits and having five phosphocholine-binding sites on the same face was complexed with 12-mercaptododecylphosphocholine. The complexes were reacted with a gold surface, which was blocked with BSA or 2-mercaptoethanol to avoid non-specific binding. CRP binding to the molecularly imprinted monolayer was investigated by surface plasmon resonance, exhibiting high sensitivity with a detection limit as low as 1 pM (0.12 ng/mL) and binding affinity (K(A) ~ 10(-7)-10(-9) M(-1)) comparable to that of immobilized anti- CRP.