Figure 4.

(A) Dependence of DAR on antibody concentration at pH 8 and pH 6. At pH 8, as antibody concentration increases, the DAR steeply decreases. At pH 6, the DAR is insensitive to antibody concentration changes. For pH 8, the concentration of SMCC-DM1 is 38 µM for all points; for pH 6, the concentration of SMCC-DM1 is 150 µM for all points. Each point is the average of 2 microscale reactions. (B) Reaction progress at pH 6 was measured by setting up a reaction in an autosampler vial and measuring the DAR of the crude reaction product by SE-UPLC at the indicated times.