Immobilization of carbohydrate epitopes for surface plasmon resonance using the Staudinger ligation

Abstract

The detection of carbohydrate–protein interactions is often performed using techniques that require surface immobilization of the lectin or the glycan. A commonly used assay for lectin binding is surface plasmon resonance (SPR). We describe an implementation of the Staudinger ligation as a method to immobilize carbohydrate epitopes to a biosensor surface. This was accomplished by first introducing an azide functionality to a carboxymethyldextran surface, followed by reaction with a phosphane-modified carbohydrate ligand. The chemistry employed is extremely mild and was easily adapted to a commercial biosensor system. Using this approach, we investigated the binding of jacalin and wheat germ agglutinin (WGA) to galactose, lactose, and N-acetyl-lactosamine. We observed that WGA binding shows evidence of multivalent interaction with the surface. Additionally, we found that jacalin binding was influenced by the presence of a flexible and hydrophobic galactosyl aglycone.