To corroborate our evolutionary hypothesis concerning the emergence of the OLEFs around the Fe2 and Fe6 sites in FeMoco, we analyzed the electrostatic environments of these potential N2-coordination sites across the entire family of FeMoco nitrogenases (cf. Gratifyingly, the same qualitative trend is observed in all of these. In fact, for the field along the Fe2-Fe6 axis, we observe that for some nitrogenases, the field strength tends to be even higher than for 3U7Q, reaching values as high as -0.5 VÅ -1 . Also noteworthy is that for one of the FeMoco nitrogenases considered, 8P8G, 52 the characteristic OLEF patterns observed for all other nitrogenases is no longer centered around Fe2 and Fe6. Instead, Fe4 and Fe5 display the OLEF features described above.