Table 2.
Sample/fit | Fa | Cu–S |
Cu–Se |
−E0 | ||||
---|---|---|---|---|---|---|---|---|
Nob | R (Å)c | DW (Å2) | Nob | R (Å)c | DW (Å2) | |||
Copper EXAFS | ||||||||
Cu(I)Met | 0.282 | 2.7 | 2.22 | 0.013 | 1.92 | |||
Cu(I)SeM | 0.472 | 2 | 2.24 | 0.009 | 0.6 | 2.38 | 0.010 | 4.20 |
Cu(II)Metd | 0.321 | 3 | 2.22 | 0.012 | 1.89 | |||
Cu(II)SeMd | 0.391 | 2 | 2.21 | 0.009 | 1.0 | 2.36 | 0.011 | 2.00 |
Sample/fit | Fa | Se–C |
Se–Cud |
−E0 | ||||
Nob | R (Å)c | DW (Å2) | Nob | R (Å)c | DW (Å2) | |||
Selenium EXAFS | ||||||||
Cu(I)SeM | 0.718 | 2 | 1.96 | 0.005 | 1.2 | 2.39 | 0.009 | 5.96 |
Cu(II)SeM | 1.031 | 2 | 1.95 | 0.005 | 1.0 | 2.36 | 0.011 | 5.04 |
F is a least-squares fitting parameter defined as
Coordination numbers are generally considered accurate to ±25%
In any one fit, the statistical error in bond lengths is ±0.005 Å. However, when errors due to imperfect background subtraction, phase-shift calculations, and noise in the data are compounded, the actual error is probably closer to ±0.02 Å
Shell occupancy values have been renormalized by multiplying by 4 (the total number of methionines, both coordinating and noncoordinating, in the protein) so as to represent the number of Cu scatterers interacting with the coordinated Se atom