A simple approach to well-defined sugar-coated surfaces for interaction studies.

Protein-carbohydrate interactions play a crucial role in many relevant biological processes, and the development of simple and reliable tools for their study is a well-recognized need. Surface-based methods are particularly attractive because they i) can effectively mimic cell-surface recognition events, ii) allow the identification of low-affinity binders, iii) are easily adaptable to high-throughput screening, and iv) require minimal sample amounts. We describe here the design and synthesis of a peptide module that efficiently captures glycans through its reducing end, by oxime ligation. Immobilization to carboxyl-functionalized supports was thereby made possible. Chemically well-defined surfaces coated with selected glycan targets were generated by this approach for surface plasmon resonance (SPR) studies. The usefulness of the method was demonstrated in the analysis of interactions that covered a five-orders-of-magnitude affinity range; namely, the strong binding (KA approximately 10(9) M(-1)) of a well-known lectin (wheat germ agglutinin) to chitopentose (GlcNAc5), and that of the same sugar with a weak binder (KA approximately 10(4) M(-1)), HEV32--the smallest hevein domain described.