Aligning Crystals

Chris Hosfield chris at crystal
Tue Jan 6 09:55:02 EST 1998

Hi all,

In the near future, we will be attempting to collect MAD data on an 
Se-containing protein and wish to do so in the 'mirror' geometry as 
opposed to inverse beam.  Our crystals are space group P21 with unit 
cell dimensions:

52, 160, 64, beta=95 degrees.

The crystal morphology suggests agreement with these parameters as 
typical crystals are about 0.4 x 0.15 x 0.10 mm.  (Though of course that 
does not ensure agreement)

Unfortunately, alignment will be done without the aid of a goniostat.

Using standard Hampton cryo-loops, the crystals tend to go into the loop 
so that the long crystal edge is aligned with the spindle axis.
In this orientation, DENZO auto-indexing can often produce a crystal roty 
near 0 degrees.  We are presuming that since this a monoclinic cell, we 
would wish to align the b* axis in the beam.  Is there any relationship 
between the alignment of b* and crystal roty in DENZO?  

In any event, I would appreciate any practical information that anyone 
has to offer.

Please reply to 

chris at

Thanks in advance,

Chris Hosfield
Queen's University	
Kingston, ON	

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