Crystallography data reduction

Now that automated diffractometers and sophisticated computer data-reduction systems have become routinely used, the task involved in conducting an X-ray crystal-structure examination has been enormously simplified. As a result, the number of structures determined each year by crystallography has escalated dramatically. The logistics of maintaining this series in the original form would now entail such stupendous demands on our space that a volume of Advances could be completely occupied by this one article alone. As the original purpose of this series... 

With the advent of faster 2D-Detectors, and the enormous amount of data produced in certain experiments, it becomes necessary to have a system which is more powerful. One such system is in development at EMBL-Hamburg with the probably most challenging X-ray experiment in mind X-ray crystallography. A high resolution 2D-Detector would produce such an amount of raw data within a short time period, that the available disk space would become a bottleneck. Therefore, a new system is now being developed around a bench of local processors, which can be programmed to do an on-line data reduction, before they are sent to the host computer. Details about the new system can be found in Ref... 

Blessing, R. H. Data reduction and error analysis for accurate single crystal diffraction intensities. Crystallography Reviews 1, 3-58 (1987). 

Amber Th +(aq) has recently been prepared from aqueous solutions of ThCLt and HN3, and is stable for over 1 h before being oxidized by water. U " can be obtained by reduction of U02 or U , either electrolytically or with Zn amalgam, but is thermodynamically unstable to oxidation not only by O2 and aqueous aeids but by pure water also. It is nevertheless possible to crystallize double sulfates or double chlorides from aqueous solution and these ean then be used to prepare other complexes in nonaqueous solvents. Crystallographie data are not plentiful but it has been shown that in (NH4)U (S04)2(H20)4 each SO is bidentate to one U and monodentate to a second. Three H2O complete a coordination sphere of 9 oxygens for each uranium with a geometry intermediate between tricapped trigonal prismatic and monocapped square antiprismatic. A number of cationic amide complexes are also known for which infrared evidence suggests ... 

All the above techniques use incident monochromatic radiation, usually focus in one or two dimensions. However for cases a) and d) the reduction of radiation damage and more particularly in kinetic crystallography the use of polychromatic data collection is yielding promising results. This technique makes combined use of the intensity and collimation of the SR beam with a large wavelength spread for Laue data colla tion from protein single crystals. 

Further reductions in exposure time and hence radiation damage in virus crystallography may accrue from the use of white beam (modified) Laue methods preliminary work on this is in progress (Bloomer and Helliwell (1985), unpublished at the SRS and Rossmann et al. at Cornell unpublished (1986)). Data collection on some virus crystals is virtually impossible in the home laboratory. 

In the last few years rapid advances have been made in the field of computational crystallography, so that it is now possible to produce highly refined computer models of a wide variety of polymeric materials using X-ray diffraction data. Unfortunately, these achievements have been negated to some extent because the techniques used to collect the data for such refinement programs have not advanced at a comparable rate. In this contribution we describe a computer program which facilitates the reduction of intensity and d-spacing data obtained by the multiple film-pack method, and attempts to quantify the errors associated with such measurements. 

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