Crystal structures of Fabs 314.1 and 314.3 and their complexes with quinine. View of the antigen-binding site of Fab 314.1 and its quinine complex (A,C,E,G) and Fab 314.3 and its quinine complex (B,D,F,H) in identical orientations. Quinine is shown in stick with carbon atoms wheat, oxygens red, and nitrogens blue (C,D) or as a wheat surface (G,H). CDR loops are colored red (H3), blue (L3), yellow (H2 and L2), and green (H1 and L1). The Fab solvent-accessible surface is transparent in panels A-D, revealing CDR loops and framework (white) shown in cartoon. In panels E-H, the solvent-accessible surfaces include quinine when present and are opaque to better show the marked differences in topography of the surfaces that occur because of both quinine binding and CDR H3 and L3 loop backbone reorientation.