Hit 21 bound deep into the active site in a part of the pocket that is not well explored by any of the known FabF inhibitors (Figure ). Although hit 21 does not establish any direct hydrogen bonds with the protein it does so through two water molecules that act as hydrogen-bond bridges between the ligand and residues Ala280 and Asp266 (Figure ). Furthermore, the pyrazole ring of the ligand is stacked on top of the side chain of Phe298 and the distance between the centres of these rings is 4.4 Å, which indicates a possible π-π interaction. While the electron density for hit 20 was clearly defined in both the Fo-Fc and PanDDA event maps, electron density for hit 21 was only visible in the PanDDA event map. To verify binding of the latter, soaking was repeated with PaFabF C164A. Soaked crystals were successfully diffracted at 1.57 Å and electron density for hit 21 was visible in both binding sites of the FabF C164A dimer. The Fo-Fc electron density map of the ligand was very clear, and the binding pose was identical to the one observed before with FabF C164Q (Figure , Figure )).