Saturday 21 January 2012

Making fixes to cif2mtz easier


From: Thomas Womack
Date: 21 December 2011 14:52

The patch in https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=CCP4BB;325e1870.1112 solves the problem with 3u57.

A few days ago I read the interesting paper http://journals.iucr.org/d/issues/2011/01/00/dz5216/dz5216bdy.html referring to a crystal structure containing a diselenide bond; I downloaded the model and structure factors for 2xsk, and cif2mtz refused to convert them.

This turns out to be because the Bijvoet pairs measured in the header were described as

 _refln.pdbx_F_meas_plus
 _refln.pdbx_F_meas_plus_sigma
 _refln.pdbx_F_meas_minus
 _refln.pdbx_F_meas_minus_sigma

while both the ccp4-6.2.0/lib/data/cif_mm.dic and the http://mmcif.pdb.org/dictionaries/ascii/mmcif_pdbx_v40.dic dictionaries require these to be

 _refln.pdbx_F_plus
 _refln.pdbx_F_plus_sigma
 _refln.pdbx_F_minus
 _refln.pdbx_F_minus_sigma

It was trivial to fix the problem with a text editor (and this is a case where the right answer is to get wwpdb to fix the sf.cif file at their end), but this led to some discussion at Global Phasing as to what could be done to make cif2mtz handle sf.cif files with unusual data items without requiring modifying and recompiling the source code each time.

A summary of where we got to is at

http://www.globalphasing.com/buster/wiki/index.cgi?CCP4cif2mtzImproveIdeas

I would appreciate any comments on how to proceed in this direction.

Tom

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