6FEA and 7ADY), do not have a close-lying histidine residue to any of the seven Fe ions that constitute the M-cluster. In terms of electrostatic environments however, we observe similar trends as for the FeMoco nitrogenases, i.e., an outward pointing OLEF around Fe2, and an inward pointing field around Fe6 (Figure ). On average, the inward pointing OLEF on Fe6 tends to be slightly more pronounced than for the FeMoco analogs. It is however interesting that this more pronounced field around Fe6 coincides with a further strengthening of the long-range electric field aligned with the Fe2-Fe6 axis, now reaching magnitudes as high as -0.7 VÅ -1 . Finally, just as previously mentioned for 8P8G, for one of the FeFeco nitrogenases, 8OIE, we observe that the characteristic OLEF patterns have shifted; this time from Fe2 and Fe6 to Fe3 and Fe7 (cf. Figure ). Overall, these observations suggest that the electrostatics around -and in between -these two sites are strongly encoded in this family of enzymes.