Crystallographic binding conformations of 1 (A) and 2 (B) complexed with nNOS (PDB id: 3B3N and 3B3O).27 The heme (orange), H4B (purple), and structural water molecules (green) involved in the binding of 1 and 2 to nNOS are shown. The active site residues and ligands are represented in an atom-type style (carbons in grey, nitrogens in blue, oxygens in red, and sulfur in yellow). The distances of some important H-bonds between the residues, structural water molecules, cofactors, and inhibitors are given in Angstroms (Å).