Figure 4.

Unbiased difference (∣F_obs∣ – ∣F_cal∣) electron density maps, calculated before inclusion of the inhibitors in the models. Shown are the refined atomic models of the aromatase complexes with (a) EXM, 3.21 Å resolution contoured at 4.5σ (PDB code 3S7S), (b) 2-butynyloxy derivative 4, 3.48 Å at 4.0σ (PDB code 4GL5), and (c) 2-pentynyloxy derivative 5, 3.90 Å at 2.7σ (PDB code 4GL7). The opening toward the active site access channel is indicated with an arrow in (a). The C6-substituted alkyne side groups of the 2-alkynoxy derivatives 4 and 5 protrude into the channel space. Some residues referenced in the text are marked. Carbon atoms are in green, nitrogen blue, and oxygen red. The viewing direction is roughly the same in all three parts.