The X-ray diffraction station at the ADONE wiggler facility: preliminary results (including crystal perfection)

Abstract

The single-crystal X-ray diffractometer installed at the PWA Laboratory in Frascati is described. The Huber four-circle goniometer is controlled by an IBM-compatible personal computer by means of a plug-in board interface based on the LSI chip Am9513. The program CS running under MS-DOS performs a wide variety of operations from random search to data collection. The angular resolution of the diffractometer is 0.0025 °, while the instrumental resolution at 8 keV, with an Si(lll) monochromator, is 0.0026 °. After preliminary tests, 2Zn insulin crystals were mounted on the diffractometer and reflections were measured using synchrotron radiation. The rocking curves show full widths at half-maxima (FWHM) in the range 0.013-0.031 ° mainly due to the mosaicity.

Improvements in lysozyme protein crystal perfection through microgravity growth

“…These values are indicated in the figures by a short horizontal line with the instrument resolution function deconvoluted out. This deconvolution is given by q = (,72 -IRF2) 1/2 where ,~R is the measured reflection rocking width and IRF is the instrument resolution function (Colapietro et al, 1992). In (c) the t' = 45 ° reflections for both the earth-grown control and the microgravity crystal are plotted on the same scale.…”

“…The station, at 45 m from the source, utilizes a double-crystal Si(ll 1) monochromator and the beam is unfocused. The angular step size of the diffractometer is 0.0001 ° with an instrument resolution function (Colapietro et al, 1992) of 0.00195 °.…”

“…The precise attention to perfection in this way is relatively new (Helliwell, 1988Colapietro et al, 1992;Fourme, Ducruix, Ries-Kautt & Capelle, 1995) and should be applied more routinely. After all, it is not inconceivable that, on earth, procedures might be developed where more perfect crystals could be grown routinely so as to match the (32570) recorded at 1.2A, resolution for a microgravity-grown crystal.…”

Protein crystal perfection and its application

“…(b) LOT practice; a 90 rotation X-ray diffraction photograph recorded at SRS station 9.5, wavelength $1 Å from concanavalin A saccharide-free crystal form space group I222, unit-cell dimensions a = 88, b = 86, c = 62 Å , diffraction resolution at the edge is 5 Å (higher resolution, d min = 3 Å , randomly set crystal diffraction pattern examples are also given in Weisgerber & Helliwell, 1993). mosaicity was investigated (Helliwell, 1988;Colapietro et al, 1992) as a direct indicator of the physical perfection of the macromolecular crystal. The mosaicity provides a simple measurement of crystal quality independent of many experimental parameters.…”

Improving the X-ray resolution by reversible flash-cooling combined with concentration screening, as exemplified with PPase

“…Although protein crystals often have low mosaicity (Helliwell, 1988;Colapietro et al, 1992;Fourme et al, 1995), the decrease in their intensity with the diffraction angle is much more pronounced than for inorganic crystals. The sharp decrease in intensity (large B-factor value characterizing thermal and static disorder in a crystal) in the case of macromolecules cannot be accounted for only by the presence of such crystal defects as twins, inclusions, vacancies, dislocations and amorphous sediment (Dobrianov et al, 1998).…”