Simple crystallography using protein diffraction images

The image below represents a 1.25-deg oscillation around the horizontal axis recorded for a protein crystal with P4(2) symmetry. The Image Plate has a diameter of 345 mm and is set perpendicular to the primary beam at 300 mm from the crystal.
Try to find the answer to each of the following problems:

1. Estimate the unit cell parameters.
2. Estimate the mosaic spread (mosaicity) of the crystal.
3. For the crystal axis that is roughly aligned with the oscillation axis, estimate its deviation from coincidence with the spindle, both in the plane of the detector and in the equatorial plane.
4. By what amount, and in what direction, would you rotate the spindle to bring one of the crystal axes into coincidence with the primary beam?

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Last update: April 1, 1999