Two-wavelength MAD phasing: in search of the optimal choice of wavelengths.
The multiwavelength anomalous dispersion (MAD) method is increasingly being used to determine protein crystal structures. In theory, data collection at two wavelengths is sufficient for the determination of MAD phases, but three or even more wavelengths are used most often. In this paper, the results of the phasing procedure using only two wavelengths for proteins containing different types of anomalous scatterers are analyzed. In these cases, it is shown that this approach leads to interpretable maps, similar in quality to those obtained with data collected at three wavelengths, provided that the wavelengths are chosen so as to give a large contrast in the real part of the anomalous scattering factor f. The consequences for a rational MAD data-collection strategy are discussed.
European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, 22603 Hamburg, Germany. ana@embl-hamburg.de
A
A
González
J
J
Pédelacq
M
M
Solà
F X
FX
Gomis-Rüth
M
M
Coll
J
J
Samama
S
S
Benini
D001426:Bacterial Proteins / Q000737:chemistry; D001427:Bacterial Toxins; D018360:Crystallography, X-Ray / Q000379:methods*; D003574:Cytochrome c Group / Q000737:chemistry; D003627:Data Interpretation, Statistical; D039621:Eukaryotic Initiation Factor-3; D005098:Exotoxins; D007956:Leukocidins / Q000737:chemistry; D008958:Models, Molecular; D010448:Peptide Initiation Factors / Q000737:chemistry; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D012542:Scattering, Radiation; D013211:Staphylococcus aureus; D014157:Transcription Factors / Q000737:chemistry
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003574:Cytochrome c Group; D039621:Eukaryotic Initiation Factor-3; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; D010448:Peptide Initiation Factors; D011506:Proteins; D014157:Transcription Factors; C083951:cytochrome c553; C061278:PhoB protein, Bacteria