Bis-sulfone-PEG4-DBCO is a bis-alkylating labeling reagent that enables site-specific incorporation of DBCO moiety onto antibodies to form well-defined conjugates. This approach involves two steps: (1) disulfide reduction to release the two cysteine thiols and (2) re-forming the disulfide by bis-alkylation via a three-carbon bridge to which DBCO moiety is covalently attached. During this process, irreversible denaturation of the protein, disrupting either their tertiary structure or their biological activity does not occur.
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).
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