One-and-a-half wavelength approach.
In many cases single-wavelength anomalous diffraction (SAD) phasing leads to a successful structure solution, but it is impossible to predict beforehand if single-wavelength data with a certain amount of anomalous signal resulting will be sufficient. It is therefore safer to continue collecting data at different wavelengths according to a MAD protocol, but to simultaneously attempt to phase the first data set by the SAD method. If this is successful, then further data collection can be abandoned. This '1.5-wavelength' approach may save a substantial amount of time and effort and diminishes the effects of crystal radiation damage. The principles of SAD phasing are illustrated using vector diagrams in the Argand plane.
Dauter
Zbigniew
Z
Synchrotron Radiation Research Section, National Cancer Institute, NSLS, Building 725A-X9, Upton, NY 11973, USA. dauter@bnl.gov
D018360:Crystallography, X-Ray; D004798:Enzymes / Q000737:chemistry*; D004950:Esterases / Q000737:chemistry; D005583:Fourier Analysis; D014453:Glucuronosyltransferase / Q000737:chemistry; D006801:Humans; D008958:Models, Molecular; D012542:Scattering, Radiation; D012697:Serine Endopeptidases / Q000737:chemistry; D013499:Surface Properties; D014961:X-Ray Diffraction / Q000379:methods*
D004798:Enzymes; D014453:Glucuronosyltransferase; D004950:Esterases; C038495:Pseudomonas serine proteinase; D012697:Serine Endopeptidases