Trapping an intermediate of dinitrogen ([N.sub.2]) reduction on nitrogenase

The intermediate generated at a high concentration during reduction of the natural nitrogenase substrate ([N.sub.2]) by wild-type MoFe protein has shown that it contains [N.sub.2] bound to the active-site FeMo cofactor. The single type of [super 15]N-coupled nucleus from the field dependence, along with the absence of an associated exchangeable [super 1]H ENDOR signal, is shown to be consistent with the [N.sub.2] molecule bound end-on to the FeMo cofactor.