Superparamagnetic adsorbents for high-gradient magnetic fishing of lectins out of legume extracts

This work presents the development, testing, and application in high-gradient magnetic fishing of superparamagnetic supports for adsorption of lectins. Various approaches were examined to produce affinity, mixed mode, and hydrophobic charge induction type adsorbents. In clean monocomponent systems affinity supports created by direct attachment of glucose or maltose to amine-terminated iron oxide particles could bind concanavalin A at levels of up to approximate to 280 mg g(-1) support with high affinity (approximate to 1 muM dissociation constants). However, the best performance was delivered by adsorbents featuring coupled tentacular dextran chains displaying a maximum binding capacity of 238 mg g(-1) and a dissociation constant of 0.13 muM. Adsorbents derivatized with mixed mode or hydrophobic charge induction ligands likewise demonstrated very high capacities for both concanavalin A and Lens culinaris agglutinin (greater than or equal to 250 mg g(-1)) with dissociation constants in the micromolar range, though neither of these systems showed any selectivity for lectins in leguminous extracts. When the affinity supports were applied to carbohydrate containing legume extracts only the dextran-linked adsorbents supplied sufficient competition to dissolved sugars to selectively bind concanavalin A in an extract of jack beans. The dextran-linked supports were employed in a high-gradient magnetic fishing experiment, in which concanavalin A was purified to near homogeneity from a crude, unclarified extract of jack beans. (C) 2004 Wiley Periodicals, Inc.