R32 transformations

Adrian Goldman, BTK x8029 GOLDMAN at ALA.BTK.UTU.FI
Thu Dec 2 10:07:24 EST 1993

We are collecting macromolecular data on an RAXIS area detector.  The
protein crystallises in two different R32 space groups related by a
halving of the z-axis: 110.4x110.4x154 and 110.4x110.4x77.  Our problem
is in aligning the crystal.  Using the automatic alignment routines
supplied by MSC/Rigaku, the protein is misindexed >50% of the time:
we get the rhombohedral net, we get one of the C2 subgroups and, sometimes,
we get the rhombohedral net corresponding to z=154 when the protein crystals
are actually the z=77 form.  

What I am looking for is a program/code fragments/suggestions for doing the
coordinate transform.  What I want to do is hand a program the misseting angles
between the crystal coordinate system and lab frame, information about which
crystal and reciprocal axes are parallel to what, and then be given back the
appropriate hexagonal misseting angles. I know that we could process the data
in whatever coordinate system we come up with and then combine the 
symmetry-related reflections but I think that will be suboptimal in terms of
data collection quality.

Any help would be _much_ appreciated.


Adrian Goldman                         |  Internet:  Goldman at Ala.BTK.UTu.Fi
Centre for Biotechnology,              |  Bitnet:    AGoldman at Finabo
P. O. Box 123,                         |  Phone:     358-21-6338029   
Turku, SF-20521                        |  Fax:       358-21-6338000   
Finland.                               |                              

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