Use of Debye-Hückel-Henry charge measurements in early antibody development elucidates effects of non-specific association.

The diffusion interaction parameter (k_D ) has been demonstrated to be a high-throughput technique for characterizing interactions between proteins in solution. k_D reflects both attractive and repulsive interactions, including long-ranged electrostatic repulsions. Here, we plot the mutual diffusion coefficient (D_m ) as a function of the experimentally determined Debye-Hückel-Henry surface charge (Z_DHH ) for seven human monoclonal antibodies (mAbs) in 15 mM histidine at pH 6. We find that graphs of D_m versus Z_DHH intersect at Z_DHH, ~ 2.6, independent of protein concentration. The same data plotted as k_D versus Z_DHH show a transition from net attractive to net repulsive interactions in the same region of the Z_DHH intersection point. These data suggest that there is a minimum surface charge necessary on these mAbs needed to overcome attractive interactions.