Data collection from crystals

Garman, E. F (1991). Modern methods for rapid X-ray diffraction data collection from crystals of macromolecules. In Methods in Molecular Biology, vol. 56, Crystallographic Methods and Protocols, Jones, C., MuUoy B. and Sanderson, M. R., eds. Humana Press. 

During data collection from crystals exposed to fragment(s), collect a data set that is complete in the low-resolution shells and has high redundancy. Also beneficial will be the highest resolution data possible, so examination of multiple crystals to select the one with suitable qualities is crucial (see Note 12). 

The importance of water in the preceding structure and theoretical considerations of its role suggested growing crystals in a water-free environment. The resulting crystals of unhydrated 1 Im were, in general, hardly suitable for X-ray analysis. Nevertheless, out of interest, data collection from a rather small crystal was attempted. The subsequent analysis gave the structural model11 u as depicted in Fig. 45. 

Xuong, N. H., Nielsen, C., Hamlin, R. and Anderson, D. (1985b). Strategy for data-collection from protein crystals using a multiwire coimter area detector. /. App. Cryst. 18, 342-350. 

Certain factors are likely to influence future analyses of more complex viruses. Crystal stability is governed by packing interactions and, as can be seen from Fig. 16.4, is, to a first approximation, inversely proportional to the square of the virus radius, presumably underl)dng the problems with crystal stability for analyses such as that of PRDl. Even assuming that well-ordered, stable crystals can be formed, technical considerations will place an upper limit on the unit cell size from which useful data can be collected. Nevertheless, with some improvements in beam and detector technology, we expect that data collection from cells up to 2000 A should be feasible for even a primitive unit cell. 

Case Study A High Resolution Data Collection from 6-phosphogluconate Dehydrogenase (6-PGDH) Crystals. 

It is not uncommon for data at low resolution to be inconclusive. Data collected from similarly treated crystals can often show inhibitor when the resolution is extended where it was not visible at low resolution. 

Until recently, only two reports existed for 1 1 adducts of silver halides with amines, namely AgT piperidine57 and Agl-morpholine.381 The first had a tetrameric cubane structure whilst the second was described as a stair polymer adduct. The range has now been extended to include 2-and 3-methylpyridine, quinoline and triethylamine.382 In each case the adduct was obtained by recrystallization of silver(I) iodide from neat base. The colourless crystals were found to lose base readily on exposure to the atmosphere and structural data were collected from crystals mounted in argon-filled capillaries, containing mother liquor. 

Generation of a three-dimensional (3D) density map requires collection of a 3D set of structure factors. The 3D data set is built up with data collected from a large number of crystals tilted at various angles. In general, only one image or diffraction... 

Table 3.2. shows that data collected from the literature for onset and flatband potentials for various pH generally are related. However, there are some discrepancies, especially for the onset potential of nanosized hematite in pH 13 solution. One may conclude that the onset and flat band potential are dependent on the crystal structure, surface morphology and electrolyte medium. The data listed in Table 3.2. are plotted and shown in Fig. 3.4. 

When more experiments were considered, a good correlation could be established between the aluminium concentration and the variation of the crystal habit. Figure 6 reports data collected from seven crystallizations. Spherulites exhibiting high-index faces existed for the higher supersaturation levels. When the aluminium content became lower than 4-5 mmol/1, (001) faces appeared, while (100) faces formed only below 2-2.5 mmol/1. 

The azide derivative was obtained by soaking the native crystals in a harvesting buffer solution containing 50 mM sodium azide for 24 hr (150). Binding of azide was indicated by a change of color of the crystal from blue to brownish. After X-ray intensity data collection, the crystals were dissolved in a solution containing 50 mM azide, 5 mM phosphate buffer, pH 5.5, and 8% MPD and the UV/visible spectrum was recorded at room temperature. 

Trends in the crystallization process development in the pharmaceutical industry is to carry out measurements at a small scale in addition to utilizing automation and high throughput systems as exemplified by the use of automated metastable zone measurement for 1 mL samples. It is expected that the future batch crystallization recipes will be designed based on the data collected from much smaller scale crystallizers than what is currently used in industry. 

Table 7.15. Coordinates of atoms in the crystal structure of Nd5Si4, fully refined by Rietveld technique using powder diffraction data collected from a ground powder employing Cu Ka radiation. The space group is P4i2,2. The unit cell dimensions are a = 7.8714(1), c = 14.8117(3) A. All sites are fully occupied. ...

X-ray data collection from proteins is usually plagued by radiation damage to the specimen crystals, and the experimenter may tend to hurry the data collection excessively. The intensity statistics on equivalent reflections are useful indicators of the diffractionist experimental technique. The root-mean-square (rms) deviation from the mean should not... 

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