The PDPH is a heterobifunctional crosslinker containing sulfhydryl-reactive pyridyldithiol and carbonyl-reactive hydrazide moieties. Pyridyldithiols react with free sulfhydryls (-SH) to form disulfide bonds. Hydrazide groups react with carbonyls (aldehydes and ketones) to form stable hydrazone bonds. Aldehyde groups can be created by periodate-oxidation of sialic acid and other sugar components of glycoprotein polysaccharides. Thus, PDPH is useful for conjugating glycoproteins and sulfhydryl-containing peptides or proteins. Likewise, PDPH is useful as a sulfhydryl-addition reagent for glycoproteins and other carbohydrates; after reaction of the hydrazide to an oxidized carbohydrate, the pyridyldithiol group can be cleaved by a reducing agent to expose a sulfhydryl group. Yet another application for PDPH is to react the primary amine of the hydrazide moiety to a carboxyl group using the crosslinker EDC.
