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Dear Paul,
I am dealing with a similar case: needle crystals,
trigonal, a=b=208, c=40 A (so the cell is a flat tile, with the short axis
along the long axis of the needle). Unfortunately, upon mounting the needles
almost invariably end up in the loop with their long axis parallel to the
spindle: which then means that I seldom get to see proper looms - and the
a*b* planes mostly appear as rows of closely separated spots, the rows being
separated by the c* distance. As the crystals are then rotated approximately
around c*, this remains the case all the way through data collection. The
indexing and integration are indeed tricky, as you mention.
However, when either by chance or by using a T-shaped loop one achieves
a
different orientation of the needle in the loop, then there are phi values at
which the images show the usual looms; and in one case, at the phi angle that
brought the long axis of the needle to point straight into the beam, I even
got a couple of frames with the full zone showing the hexagonal 2D a*b*
lattice.
Of course what we would (all) profit from is a kappa goniostat...
I hope this helps - good luck! and best wishes
Pietro
--
Pietro Roversi - Laboratory of Molecular Biophysics - Biochemistry Dept.
University of Oxford - South Parks Road - Oxford OX1 3QU - England, UK
Tel. 0044 (0)1865 275385 - Fax. 0044 (0)1865 275182
http://biop.ox.ac.uk/www/lea/website/index.htm
