Fig. 2.

Spectroscopic and structural analysis of phenols bound to pKSI D40N. (A) ¹⁹F NMR spectra and chemical shifts of the 4-F group for F-substituted phenols bound to KSI at pH 7.2 (black peaks) or free in solution (red dashes) at pH 2 (neutral) or pH 12 (ionized). Phenol pK_a values are shown in parentheses. (B) Superposition of the 1.30-Å resolution D40N–3-F-4-NO₂-phenol (carbon atoms are colored green; PDB ID code 3VGN) and 1.25-Å resolution D40N–phenol (carbon atoms are colored cyan; PDB ID code 2PZV) X-ray crystal structures. Oxygen, nitrogen, and fluorine atoms are colored red, blue, and magenta, respectively.