To confirm this reasoning, we also computed the OLEFs when the charges belonging to any residue within a radius of 4 Å around the cofactor are discarded (see Section S3 of the Supporting Information). As expected, a consistently outward-pointing field is indeed retained in this case. Note that the diffuse nature of the computed fields also means that local distortions of the region of the protein matrix in direct contact with the FeMoco cofactor during the catalytic cycle -which would be revealed by molecular dynamics calculations -are highly unlikely to completely disrupt the observed pattern.