Advice needed: optical diffraction

Fri Nov 11 21:11:43 EST 1994

Dear Colleagues,

     I'm not a subscriber to this list (only Methods, Proteins), but I'd
like to ask for some help.  We've crystallized a protein as needles, fixed
them with glutaraldehyde, negatively stained with uranyl acetate, and then
done electron microscopy on the "crystals".  We have imaged the surface
and get (crudely rendered) the following optical diffraction pattern from
the em negatives:
			.     .
                     .     .     .
                  .     .     .     .
                     .     x     .             
                  .     .     .     .
                     .     .     . 
                        .     . 

The angle (alpha) for this was measured at 86.5 degrees.  Reflections are
elliptical, horizontally.  I know a bit of crystallography, but am by no
means an expert.  So, my question is, can you tell the crystal system and
plane group from this pattern?  (d spacings in both dimensions are nearly
the same).  How exactly would this be determined?  Thanks a _bunch_ in
advance for your help.  Please reply to my email address below.  If anyone
expresses the interest, I'd be glad to post a summary to the
protein-crystallography list.  Best regards,  Shaun

  = Shaun D. Black, PhD   | Internet address:     shaun at = 
  = Dept. of Biochemistry | University of Texas Health Center, at Tyler = 

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