PDP-Pfp, or 3-(2-Pyridyldithio)propionic acid pentafluorophenyl ester, is a specialty reagent used primarily in bioconjugation chemistry. It facilitates the attachment of the PDP group to primary amines on proteins, peptides, or other biomolecules via its reactive pentafluorophenyl ester, which acts as an excellent leaving group for efficient amide bond formation under mild aqueous conditions. The pyridyl disulfide (PDP) moiety enables subsequent thiol-disulfide exchange reactions with cysteine residues or thiol-containing molecules, allowing for reversible and site-specific conjugation. This reagent is widely applied in the preparation of antibody-drug conjugates, immunotoxins, biosensors, and protein modifications in biotechnology and pharmaceutical research.