Specific Modification of Protein Sulfhydryl Groups with α,β-Unsaturated Compounds

Abstract Reaction rates with acrylic acid derivatives were determined for —SH groups in mercaptoethanol and in mercaptoethanol-reduced wheat gluten and bovine serum albumin. The disappearance of —SH and NH2 groups is a direct function of pH in the range 6 to 8 and of acrylate concentration. Kinetic studies indicate that protein —SH groups are modified more rapidly than the mercaptoethanol —SH group. Conditions for specific alkylation of protein —SH groups are pH 7 and a 1:1 ratio of vinyl compound to total protein and mercaptoethanol —SH groups. Under these conditions, the reaction is complete in 5 min with methyl acrylate, 20 min with acrylonitrile, and 100 min with acrylamide.