Crystallography data processing

Tsuruta, H., et al. (1998). Imaging RNA and dynamic protein segments with low-resolution virus crystallography experimental design, data processing and imph-cations of electron density maps. /. Mol. Biol. 284, 1439-1452. 

Computational crystallography has today a much broader scope and meaning than it had 20 years ago, when it was stUl mostly restricted to algorithms and software for X-ray data processing. The following is a brief summary of highlights. 

Otwinowski, Z. (1992). An Oscillation Data Processing Suite for Macromolecular Crystallography, Yale University, New Haven. 

Greenhough, T. J., and Suddath, F. L. Oscillation camera data processing. 4. Results and recommendations for the processing of synchrotron radiation data in macromolecular crystallography. J. Appl. Crysi. 19, 400-409 (1986). 

Tel. 44-925-603528, fax 44-925-603100, e-mail ccp4 daresbury.ac.uk Suite of almost 100 protein crystallography programs for data processing, scaling, Patterson search and refinement, isomorphous and molecular replacement, structure refinement, such as PROLSQ, phase improvement (solvent flattening and symmetry averaging), and presentation of results, such as SURFACE for accessible surface area. Available via ftp from anonymous ... 

Structure of the DNA pol III b subunit clamp based on X-ray crystallography data. (A) The two b subunits form a protein "clamp" which appears to wrap around the DNA helix. This arrangement explains its role as the processivity factor because it prevents the catalytic subunit of DNA pol III from dissociating with the DNA. (B) The structure of the eukaryotic processivity factor, PCNA, also forms a clamp around the DNA, but it is made up of three subunits. 

Parameters of the source that need to be considered include the wavelength range, the emittance (source size x divergence), the stability of the source, the circulating current and the lifetime of the beam. To date the polarisation of the beam has been taken account of in data processing but not specifically designed for a macromolecular crystallography experiment. 

Figure 1.3 shows the procedure for structure determination by X-ray crystallography and Table 1.6 lists software used in structural analysis (data processing, molecular replacement, heavy atom site identification, model building, refinement and validation). 

A number of synchrotrons (including the National Synchrotron Light Source, New York, the Advanced Light Source, Berkley, and soon the Canadian Light Source, Saskatoon) operate mail-in crystallography services where a scientist can mail in crystals (prefrozen and mounted on loops) and data will be collected, processed (sometimes), and returned. This is becoming a method of choice, as it eliminates the need to travel to a synchrotron and speeds up the data collection procedure at the synchrotron also. 

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