Carbohydrate–protein interactions at interfaces: synthesis of thiolactosyl glycolipids and design of a working model for surface plasmon resonance

Abstract

Thiolactosyl lipids designed for carbohydrate-protein binding studies have been synthesised. One representative was selected for binding studies with a plant lectin RCA₁₂₀, the agglutinin from Ricinus communis. The interactions were measured quantitatively in real time using a BIAcore surface plasmon resonance instrument. Removal of much of the galactose from the thiolactosyl lipid in situ with β-galactosidase showed that the lectin binding was highly specific. A dissociation constant K_D = 8.77 × 10⁻⁸ M was measured for 1-{2-[2-(2-[β-D-galactopyranosyl-(1 → 4)-1-thio-β-D-glucopyranosyl]ethoxy)ethoxy]ethoxy}octadecane 30 which is four orders of magnitude greater than that determined for binding to lactose in solution. A concentration of lactose of >80 mM was required to block the lectin binding to thiolactosyl lipid in a neomembrane.