Gel-Immobilized Heparin-Binding Lectin as Sensitive Sensor for Certain Groups of Charge-Bearing Carbohydrates

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Abstract
The specificity of lectins to carbohydrate moieties in principle enables them to serve as sensors for sugars with ligand properties. However, experimental systems and parameters to measure this interaction need to be defined. On the basis of knowledge about temperature-sensitive volume changes of gels, composed of acrylamide derivatives, and about the influence of presence of charge-bearing groups within the gel on this behavior, we covalently immobilized a human heparin-binding lectin into a gel matrix. Besides the lectin-carrying derivative N-isopropylacrylamide and N,N'-methylenebisacrylamide are the monomeric constituents of the polymer. The lectin has been attached to divinyl sulfone-activated N-hydroxymethylacrylamide. Several anionic sugar moieties are added to the solution, covering the gel pieces, and the mechanical response of the individual gel slices in dependence to stepwise temperature increases is automatically recorded with an electronic transducer at a sensitivity of 5 mV/microns. Only carboxyl group-containing sugar moieties like glucuronic acid notably reduce the extent of the temperature-dependent gel shrinking as indicator for a protein-carbohydrate interaction. The individual slices are reuseable, emphasizing practical applications. This sensitive and automated assay concept with the covalently immobilized heparin-binding protein is supposed to be adaptable to other groups of lectins with specificity to anionic sugars like sialic acid-binding proteins.