Triclinic data set on a Small MAR

A data set has been collected on a crystal of protein Z. The data were collected by Raimond Ravelli and Gitay Kryger, May 1996, at X11 of the EMBL DESY-Hamburg synchrotron with a Small Mar detector. The spindle axis comes from the right seen from the direction of the beam, and lies with the beam in the horizontal plane.

The unit cell of the crystal is 41.1 67.3 87.8 87.8 85.8 84.4, spacegroup P1. The wavelength was , the crystal to detector distance 225 mm. No theta offset was used: x beam 91.1 y beam 90.3. A full 180 degrees oscillation was done by recording 120 frames with an oscillation range of 1.5 degrees each. Dataprocessing of these frames (indexing, refinent, integration, scaling merging of the intensities) using DENZO and SCALEPACK gave the following redundancy table:

    Shell            Summary of observation redundancies by shells:
  Lower Upper      No. of reflections with given No. of observations
  limit limit     0     1     2     3     4   5-6   7-8  9-12 13-19   >19  total
  40.00  5.81    16    94  1909     0     0     0     0     0     0     0   2003
   5.81  4.62    13   106  1900     0     0     0     0     0     0     0   2006
   4.62  4.03    16    81  1927     0     0     0     0     0     0     0   2008
   4.03  3.66    18    93  1920     0     0     0     0     0     0     0   2013
   3.66  3.40    19    80  1902     0     0     0     0     0     0     0   1982
   3.40  3.20    21   107  1908     0     0     0     0     0     0     0   2015
   3.20  3.04    26    99  1915     0     0     0     0     0     0     0   2014
   3.04  2.91    24   135  1860     0     0     0     0     0     0     0   1995
   2.91  2.80    26   119  1871     0     0     0     0     0     0     0   1990
   2.80  2.70    36   129  1874     0     0     0     0     0     0     0   2003
 All hkl        215  1043 18986     0     0     0     0     0     0     0  20029

More interesting than the small discrepancy between the observed and the predicted redundancy table, are the alternatives if one would not have enough time left on a sunchrotron to collect a full 180 degrees dataset. A few of them are listed in the following table. The use of the command LEAPFROG is indicated by specifing the value of the sweep and the step.

  
Table: Minimal oscillation ranges for different completenesses for datacollection on protein Z

The starting (and so the ending) oscillation angles are completely irrelevant for P1: since there is no other symmetry than an inverse centrum in reciprocal space, it does not make any difference where to start. What can be learned from the table is that it favourable for this protein to collect the data according to the LEAPFROG method with relative large sweeps and steps if the goal is to obtain just a reasonable completeness in the shortest time possible.