Proteins containing reductively aminated disaccharides: chemical and immunochemical characterization

Synthetic glycoproteins can be prepared by reductive amination of proteins and reducing carbohydrates in the presence of sodium cyanoborohydride. The reaction proceeds readily in aqueous solution at pH 6--9 to give high degrees of substitution. The degree of substitution can be determined by amino acid analysis, as the 2 degrees amine linkage formed with the epsilon-amino groups of lysine is stable to acid-catalyzed protein hydrolysis conditions. Antisera have been obtained to bovine serum albumin conjugates containing reductively aminated cellobiose, lactose, and maltose. Preliminary experiments demonstrate that antiserum to the cellobiose-BSA conjugate is hapten-specific, and the structural features of the hapten recognized by the antibodies were established by hapten inhibition experiments. These studies demonstrate that antibodies recognize both the terminal beta-glucosyl and acyclic reduced glucosyl residues.