Table 3.
Three-Fe path fits for the Fe K-edge EXAFS data of NifH, VnfH and AnfH over the k-range of 2–16 Å−1. Coordination number (N), interatomic distance (R, Å), mean-square thermal and static disorder in distance (σ2, Å2), and EXAFS threshold energy adjustment from 7030 eV (ΔE0, eV) were varied in the fits. Estimated errors are ± 0.02 Å in R, ± 0.0001 Å2 in σ2, and ± 20% in N. The goodness of fit, F, is defined as F = [Σk6(χexper. − χcalc.)2/Σk6(χexper.)2]0.5.
| NifH | VnfH | AnfH | |||||||
|---|---|---|---|---|---|---|---|---|---|
| N | R(Å) | σ2 (Å2) | N | R(Å) | σ2 (Å2) | N | R(Å) | σ2 (Å2) | |
| Scatterer | |||||||||
| Fe-S | 4 | 2.29 | 0.0058 | 4 | 2.32 | 0.0049 | 4 | 2.32 | 0.0049 |
| Fe-Fe | 0.5 | 2.46 | 0.0010 | 0.5 | 2.52 | 0.0050 | 0.5 | 2.53 | 0.0018 |
| Fe-Fe | 1 | 2.62 | 0.0020 | 1 | 2.68 | 0.0540 | 1 | 2.72 | 0.0456 |
| Fe-Fe | 1.5 | 2.74 | 0.0017 | 1. 5 | 2.72 | 0.0051 | 1. 5 | 2.72 | 0.0048 |
| ΔE0 (eV) | −13.3 | −12.2 | −12.3 | ||||||
| Weighted F | 0.188 | 0.165 | 0.183 | ||||||