Fig. 3. (A) Scheme for the synthesis of tetraazide poly(ethylene glycol) along with coumarin functionalization and maleimide installation. Yields noted in the polymerization process are reported as the individual, elongation reactions, not the overall yield. (B) Mass spectrometry of digested and reduced antibody–coumarin conjugate. Red stars represent the number of polymers modifying each antibody subunit. (C) Activity of trastuzumab and coumarin conjugate towards HER2 antigen as measured by ELISA.