Table 5. Tetragonally distorted hexacoordinated Cu coordination distances and DebyeWaller factors as refined from constrained EXAFS of copper insulin compared with crystallographic values.
The constrained EXAFS does not distinguish between sites I and II.
| XRD | Constrained EXAFS† | |||
|---|---|---|---|---|
| R ‡ () | R 1 () | R 2 () | 22 (2) | |
| N2 (HisB10) | 2.10 | 1.98 (1) | 2.02 (1) | 0.002 (1) |
| C1 | 3.01 | 3.08 | 2.98 | 0.012 (5) |
| C2 | 3.15 | 2.97 | 3.16 | 0.012 (5) |
| N1 | 4.17 | 4.16 | 4.13 | 0.016 (3) |
| C | 4.25 | 4.11 | 4.22 | 0.016 (3) |
| C | 5.68 | 5.53 | 5.67 | 0.016 (3) |
| Ow | 2.25 (site I, 6-coordinated) | 2.17 (2) | 2.37 (2) | 0.011 (5) |
| Ow | 2.67 (site II, 4-coordinated) | |||
†
In the tetragonally distorted hexacoordinated geometry the distances to ligands in the tetragonal plane (R 1) are refined separately from the axial ligands (R 2), whereas the DebyeWaller factors are grouped. The occupation numbers N of histidine ligands and water ligands are 2 in the plane and 1 on the axis.
‡
Average distances from Cu to histidine and water atoms of both Cu sites in the crystal structure.
§
The rotation angle of the histidine unit around an axis orthogonal to the imidazole plane passing through the N2 atom was included in the refinement.