Map self-validation: a useful discriminator of phase correctness at low resolution.
A new map-validation procedure is based on the correlation-coefficient agreement between the observed structure-factor magnitudes and their extrapolated values from suitably modified electron-density maps from which they have been each in turn systematically excluded. The correlation coefficient tends to a maximum as the phase errors in a map are reduced. This principle was used to resolve the single-wavelength anomalous scattering (SAS) and single-derivative isomorphous replacement (SIR) phase ambiguity for a number of error-free trial structures. Applications employing real data sets tend to be more difficult owing to data incompleteness and errors affecting the construction of the Argand diagram.
Hauptman-Woodward Medical Research Institute Inc., 73 High Street, Buffalo, NY 14203, USA. langs@algol.hwi.buffalo.edu
D A
DA
Langs
R H
RH
Blessing
D
D
Guo
D003461:Crystallography / Q000379:methods*; D003574:Cytochrome c Group / Q000737:chemistry*; D004583:Electrons; D008958:Models, Molecular; D010231:Paracoccus denitrificans / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055672:Static Electricity
D003574:Cytochrome c Group; C031732:cytochrome C-550