Enlarged focused view of interactions between the globular head and 3C11 Fab and AVFluIgG01 Fab. In the four panels, the globular head is colored in gray, and the key structure elements (120 loop, 160 β-strand, and 240 β-strand) are colored in green. The heavy and light chains of 3C11 Fab are colored in orange and pink (A and B), and the heavy and light chains of AVFluIgG01 Fab are colored in cyan and magenta (C and D).