Table 1.

Fits obtained to the Cu K-EXAFS CusF and CusB SeM derivatives by curve-fitting using the program EXCURVE 9.2

	F a	Nob	R (Å)c	DW (Å2)	Nob	R (Å)c	DW (Å2)	Nob	R (Å)c	DW (Å2)	E 0
Copper edge		Cu-N(His)d			Cu-S			Cu-Se
WT CusF M8IM59I	3.08	1	2.00	0.003				2	2.38	0.007	−3.3
WT CusB	0.93							3	2.41	0.007	−5.0
Intermediate SeM-CusF	1.49	1	1.98	0.009	1	2.26	0.011	1	2.43	0.009	−2.9
Intermediate SeM-CusB	2.3				1	2.25	0.010	2	2.43	0.009	−3.0
Se edge		Se-C						Se-Cu
WT CusF M8IM59I	0.47	2	1.97	0.005				1	2.38	0.005	−6.6
WT CusB	0.83	2	1.96	0.004				1	2.42	0.005	−5.5
Intermediate SeM-CusF	1.78	2	1.97	0.007				0.6	2.42	0.006	−6.3
Intermediate SeM-CusB	1.51	2	1.96	0.004				0.53	2.44	0.009	−4.9

WT wild type

^aF is a least-squares fitting parameter defined as $F^2=\frac{1}{N}{\sum }_{i=1}^N{k}^6{\left(\mathrm{Data\; -\; Model}\right)}^2$

^bCoordination numbers are generally considered accurate to ±25%

^cIn 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

^dFits included both single and multiple scattering contributions from the imidazole ring