Carbodiimide-mediated conjugation of hippuric acid to concanavalin A: retention of ligand binding and hemagglutinating activities.

Conditions for conjugating small molecules with reactive carboxyl groups to concanavalin A (ConA), with retention of biological activity of the lectin, are described. Hippuric acid was conjugated to reactive amino groups on ConA with N-ethyl-N'-(dimethylaminopropyl) carbodiimide under conditions in which neither inter- nor intra-molecular cross-linking was detectable. These same conditions provided for the loading of variable amounts of hippurate as a function of reaction time; conjugates were synthesized with 9.6 mol hippurate.mol ConA-1. Conjugation in the presence of 0.1 M phosphate provided a condition for limiting the extent of coupling; only amide linkages were formed. These conjugates retained both the ability to bind ligands and the hemagglutination titer of the native lectin.