Figure 4.

A decysteinylated C80 can be efficiently conjugated to maleimides with no impact on antigen binding affinity (A) Mass spectrometry analyses of the light chain of decysteinylated xi155D5 conjugated with maleimido-PEG₂-biotin. Efficiency of conjugation was 94%. (B). Mass spectrometry analyses of the light chain of decysteinylated xi155D5, xi155D5 conjugated with maleimido-PEG₄- DBCO, and xi155D5-DBCO conjugated with azido-chlorothiazide via SPAAC. Efficiency of maleimido addition to the light chain was 85%. SPR analysis of the binding affinity of cysteinylated, decysteinylated, and decysteinylated/conjugated mAb to soluble CA9 indicated that the decysteinylation procedure as well as subsequent conjugation to C80 had no impact on binding affinity of the xi155D5 antibody to antigen.