Considerations for the refinement of low-resolution crystal structures

DeLaBarre, B.; Brunger, A.T.

doi:10.1107/S0907444906012650

Figure 2
(a) The effect of applying B-factor sharpening to electron-density maps (1)

. A σ_A-weighted phase-combined 2F_o − F_c map was calculated to 4.4 Å using the refined model of p97/VCP–ADP·AlF_x and selenomethionine-derived experimental MAD phases (obtained at 6.5 Å resolution). The map is shown around a homologous stretch of residues in the D1 (residues A251–A261) and D2 domains (residues A525–A534) of p97/VCP. The D2 domain was less ordered than the D1 domain and exhibited slightly different behavior with application of increasingly negative B-factor sharpening. The representative electron-density maps depicted here show that there is minimal discontinuity with maximum side-chain definition at the `best' B_sharp value of −120 Å² (indicated by the dashed box). (b) The best B_sharp value of −120 Å² is also obtained by determining the minimum absolute B_sharp value where the Wilson plot [ln(〈F_sharp〉²/〈f_i〉²) versus resolution] produces all-positive values (dashed line). The Wilson plot was computed with ∼1000 reflections per bin. f_i is the expected contribution of individual atoms in the unit cell to the scattering vector.

BIOLOGICAL
CRYSTALLOGRAPHY

ISSN: 1399-0047

Volume 62| Part 8| July 2006| Pages 923-932

doi:10.1107/S0907444906012650

Search term		doi		Advanced search
Author		volume	page