The use of SnB to determine an anomalous scattering substructure.
The positions of eight Se atoms in a selenomethionyl 35 kDa protein were determined at 2.0 and 2.5 A resolution using the direct-methods program SnB. Data at the selenium peak, edge and remote wavelengths were measured and processed independently. Anomalous difference E magnitudes at each wavelength were derived by two different procedures: renormalized diffE values were calculated according to the equation diffE = ¿sigma[(f + f')2 + f"2]||E+|-|E-||¿1/2/2q(sigma f"2)1/2, where q is a least-squares fitted renormalization function of sinstraight theta/lambda such that <diffE2> = 1.0; and difference E magnitudes were calculated from DeltaF2. Locally normalized E magnitudes corresponding to |FA| were also derived from the combination of the data at all three wavelengths through the use of the MADSYS program suite. Each of the independent sets of anomalous difference E magnitudes was capable of producing the correct solution, as did the E data obtained from the FA data. Higher success rates with SnB were observed for the 2.0 A peak and edge diffE data.
Hauptman-Woodward Medical Research Institute, 73 High Street, Buffalo, NY 14203, USA, and Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA. smith@hwi.buffalo.edu
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D015933:Complement C3d / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D012984:Software; D017356:Synchrotrons
D015933:Complement C3d