[Chimera-users] problems loading .mtz files

Tom Goddard goddard at sonic.net
Wed Aug 25 11:32:46 PDT 2010

Hi Rakesh,

   An MTZ file contains structure factors, not a density map.  Basically 
a Fourier transform is needed to get the density map from the structure 
factors.  There is a Chimera feature request (#201)


to have Chimera calculate the map from the structure factors.  It is not 
an entirely trivial calculation since symmetry and missing structure 
factors must be accounted for.  Chimera density map features are aimed 
at electron microscopy rather than x-ray crystallography and Chimera is 
missing useful features for x-ray maps.  For example Chimera will not 
automatically periodically extend a unit cell map to cover a display 
molecule as COOT does.  For now you'll need to calculate the density map 
using other software.


> Hi,
> i am having problems loading electron density files from CCP4 and Phenix. The
> error message reads "Bad MRC grid size (129737328,-319356160,1145110528)". Please
> advise.
> Cheers
> Rakesh
> Graduate student
> Dept.of Biochemistry
> Purdue University

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