Figure 7. Proposed possible orientations of the IgG1 dimer. Cartoon representations of proposed possible dimer orientations based on the hydroxyl radical footprinting data. The bottom mAb has heavy chains in gray and light chains in black. The top mAb has heavy chains in light blue and light chains in dark blue. Head-to-head orientation allows for the light and heavy chains of the dimer to associate with each other in the interface region. (A) Cartoon depiction of a head-to head, a single-arm bound Fab-to-Fab dimer. (B) Cartoon depiction of a head-to head, double arm-bound Fab^ʹ2-to-Fab^ʹ2 dimer.