Mechanistic insights into nitrogen fixation by nitrogenase enzymes

The active catalytic site for biological nitrogen fixation is identified as an Fe-edge site underneath a vacated belt-sulfur atom (μ₂ S) of the FeMoco cluster in nitrogenase. The evolution of the μ₂ S as H₂S is critical to electrochemically activating the inert N₂, while its readsorption is required to dissociate the strongly bound NH₃*. The reversible hinge-like behavior of the μ₂ S provides an analog to the high temperatures and pressures required in industrial ammonia synthesis in the Haber–Bosch process.