This invention relates to water-soluble/dispersible reactive functionalized imido and polyimido compounds, wherein the polyimido compounds may be selected from the group consisting of polysuccinimide compounds, polyglutimide compounds, and copolymers of thereof. The polyimido compound comprises a functionalizing moiety F that provides functionality to the polyimido compound and is preferably derived from a nucleophilic moiety selected from the group consisting of amines, alcohols, phenols, thiols, and carboxylates; and a water-solubilizing/dispersing moiety that provides water-solubility and/or water-dispersibility to the polyimido compound and is preferably derived from a nucleophilic moiety selected from the group consisting of amines, alcohols, phenols, thiols, and carboxylates. The invention also pertains to a proteinaceous substrate to which the imido or polyimido compound has been covalently bonded and to a method for treating a proteinaceous substrate with the imido or polyimido compound.