Figure 3.

The active site crystal structure of nNOS with 2b bound (PDB code: 3N2R) showing some relevant hydrogen bonds as dashed lines. The 2Fo-Fc (gray) and Fo-Fc (red) electron density map of 2b are contoured at 1.0 σ and −3.0 σ, respectively. Although crystals were soaked in a racemic mix of 2b, the electron density is consistent with only the (3R,4R) enantiomer. The pyrrolidine ring nitrogen of the (3S,4S) enantiomer would have directly hydrogen bonded to Glu592, replacing the position of Wat1. The electron density for the aminopyridine group is very clear and partially so for the pyrrolidine. However, there is no electron density for the phenoxyphenyl tail, indicating disordering and, therefore, the absence of any tight protein-phenoxyphenyl interactions.