On the routine use of soft X-rays in macromolecular crystallography. Part III. The optimal data-collection wavelength.
Complete and highly redundant data sets were collected at different wavelengths between 0.80 and 2.65 A for a total of ten different protein and DNA model systems. The magnitude of the anomalous signal-to-noise ratio as assessed by the quotient R(anom)/R(r.i.m.) was found to be influenced by the data-collection wavelength and the nature of the anomalously scattering substructure. By utilizing simple empirical correlations, for instance between the estimated deltaF/F and the expected R(anom) or the data-collection wavelength and the expected R(r.i.m.), the wavelength at which the highest anomalous signal-to-noise ratio can be expected could be estimated even before the experiment. Almost independent of the nature of the anomalously scattering substructure and provided that no elemental X-ray absorption edge is nearby, this optimal wavelength is 2.1 A.
Mueller-Dieckmann
Christoph
C
EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany.
Panjikar
Santosh
S
Tucker
Paul A
PA
Weiss
Manfred S
MS
D000818:Animals; D018360:Crystallography, X-Ray / Q000379:methods*; D004247:DNA / Q000737:chemistry; D003625:Data Collection; D011506:Proteins / Q000737:chemistry
D011506:Proteins; D004247:DNA