Figure 7. The sequence of modeled positions for NH₃ from the reaction face of FeMo-co towards the protein surface.

Cyan spheres are the locations of the N atom: H atoms are not shown (but are included in Supplementary Figs. S2, S3). Orange spheres are water. Key interacting amino acids are marked and labeled. The side chain CH₃ of Thr^58A (circled) is significant, because the lone pairs of NH₃ looping around it are 2.6–2.9Å distant, with the potential for formation of weak C-H → NH₃ hydrogen bonds. All protein chains are included and are coloured by structure (α-helix green, extended-β yellow, turn orange, coil red), revealing the minimal secondary structure around most of the proposed NH₃ pathway.