Accurate cells from area-detector images

Abstract

A procedure is described, for an Eulerian or Kappa goniostat, to determine the exact spindle value 9 at the moment of impact of a re¯ection on an area detector; such information is essential for the calculation of accurate re¯ection vectors and, eventually, the unit-cell and lattice orientation. The method is based on a comparison of re¯ection impact coordinates on two related images. One image is obtained by spindle rotation over a few degrees (`9 scan') and the other by the same 9 rotation, but with a superposed rotation (1) perpendicular to the ®rst (`9/1 scan'). In both cases, the spindle is kept perpendicular to the primary beam, i.e. 3 = 0 or 180 . Therefore, on the second image, exactly the same re¯ections as on the ®rst will appear, but on a different spot on the detector. From the tangential separation between corresponding re¯ection impacts, the moment of impact (9 value) is calculated. The method is especially useful in small-molecule work, where rather wide scans are required for a reasonable number of re¯ections in one image. It is shown that for our purpose the Eulerian 9/1 scan can be simulated practically exactly by simultaneous uniform rotations of the axes 3 K , and 9 K of the Kappa goniostat.

Directed anisotropy in bis(acetato-κ2O,O′)diaquazinc(II) at 110 and 250 K

“…4). To minimize diffractometer errors in the cell determinations, we used the Phi/Phi-Chi routine (Duisenberg et al, 2000) and kept the position of the detector fixed. The largest change is found for the a axis, which is the direction of the weakest intermolecular interactions.…”

Solvent behaviour in flash-cooled protein crystals at cryogenic temperatures

“…Before initiation of the warming and cooling protocol in both types of experiment, a single data set was collected with a total exposure time of 20 min from each¯ash-cooled crystal in order to determine accurate unit-cell parameters by applying the 9±1 method (9 = 1, 1 = 5 ; Duisenberg et al, 2000) at four different 9 positions 90 apart, so as to provide data as input for the autoindexing program DirAx (Duisenberg, 1992). The resulting orientation matrix was then continuously re®ned using DENZO (Otwinowski & Minor, 1997) against the data collected at the different temperatures during the warming and cooling procedure.…”

(3R,3aR,6R,6aR)-Hexahydrofuro[3,2-b]furan-3,6-diyl dibenzoate

“…Data collection: COLLECT (Nonius, 1999); cell refinement: DIRAX/LSQ (Duisenberg et al, 2000); data reduction: EVALCCD (Duisenberg et al, 2003); program(s) used to solve structure: SIR97 (Altomare et al, 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: WinGX (Farrugia, 2012 Carbohydrate-based synthons have been used in a number of syntheses of complex natural chiral substances (Hanessian, 1993). Manipulation of the oxygenation pattern and stereochemistry of simple sugars proved to be a powerful mean to use nature-generated chirality.…”