Density Functional Study of the Electric Hyperfine Interactions and the Redox-Structural Correlations in the Cofactor of Nitrogenase. Analysis of General Trends in 57Fe Isomer Shifts

The influence of the interstitial atom, X, discovered in a recent crystallographic study of the MoFe protein of nitrogenase, on the electric hyperfine interactions of 57Fe has been investigated with density functional theory. A semiempirical theory for the isomer shift,(delta), is formulated and applied to the cofactor. The values of (delta) for the relevant redox states of the cofactor are predicted to be higher in the presence of X than in its absence.