Figure 3.

X‐ray crystal structure (1.58 Å resolution) of biotin‐phenol leaving group (7, grey) bound to avidin. a) Flexible loop regions around nitrophenolate moiety with proximal (<12 Å from phenolate) nucleophiles (Nu) on a single monomer unit shaded in purple including residues S41,102, T40,113, and K111. Monomer A and C are shaded lavender and light green, respectively. b) Highlight of residues A39, S101, R114 (lime green) directly implicated in stabilizing nitrophenolate in the avidin binding pocket. c) View showing electrostatic surface. Distance between ligand bound to monomer A and C is only 8.4 Å between the aryl rings. This view also shows how the nitrophenolate moiety is positioned just outside the binding pocket in a solvent accessible region.