4,7,10,13-Tetraoxa-16-azaheptadecanoic acid, 17-[4-[3-[(4-methylphenyl)sulfonyl]-2-[[(4-methylphenyl)sulfonyl]methyl]-1-oxopropyl]phenyl]-17-oxo-, 2,5-dioxo-1-pyrrolidinyl ester

Bis-sulfone-PEG4-NHS Ester is a bis-alkylating labeling reagent that is selective for the cysteine sulfur atoms from a native disulfide. These reagents undergo bis-alkylation to conjugate both thiols derived from the two cysteine residues of a reduced native disulfide bond such as the interchain disulfide bonds of an antibody. The reaction results in covalent rebridging of the disulfide bond via a three carbon bridge leaving the protein structurally intact. The hydrophilic PEG spacer increases solubility in aqueous media.