Bis-sulfone NHS Ester

Bis-sulfone 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 covalent, site-specific conjugation of PEG to a polyhistidine tag (His-tag) on a protein with bis-alkylating reagents was also reported in literature (see Selected References section).