Site-specific photo labelling of IgG

Conventional ways of conjugating antibodies render heterogeneous products with several populations that have different labels. We have engineered one of the domains of Protein A and Protein G and utilized their inherent affinity for IgG to achieve domains that can be covalently coupled to the Fab or Fc fragment.

Introduction of the unnatural amino acid p-benzoylphenylalanine in the sequences enables the formation of covalent bonds to the nearby antibody when the complex is exposed to long wave UV light. The domains have been equipped with a unique cysteine for easy coupling to virtually any kind of functional ligand.

We have used our domains to label antibodies of both human and mouse origin of several different subclasses and have also showed the labelled antibodies to be functional in a standard sandwich ELISA as well as in an NK-cell based ADCC assay.