RE: [ccp4bb]: problem with refinement

["Frank Vondelft" <Frank.Vondelft@syrrx.com>]

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> > Looking for some help here with the refinement on a small protein
> > structure. (does not look like CCP4 related, sorry)
> > 
> > I was able to fit the AA into the solvent-flipped density 
> > map from CNS - everything looks just wonderful except for 
> > one five-residue loop. However, shelxl refinement does not 
> > like this model, returning R(free) around 50% at 1.8A 
> > resolution. Any suggestions, anyone? Thanks very much!
> > 
> > BTW, does this have anything to do with these two facts: 1) 
> > the space group is I432; and 2) the model is being refined 
> > against Se-Met data without merging Friedel mates?
> > 
> 
> 
> shelxl isnt very happy at 1.8A - why nor use REFMAC or CNS - both
> faster and more appropriate at this resolution? 
>   Eleanor

I feel I must take exception -- at least, with the first part of that
statement: shelxl does a rather good job even at 3A, particularly with
geometries.  But I can't argue with the 'faster' thing...  lest this
degenerate into a flame war ;-)

As to why shelxl craps out... hard to tell, it could be anything:
mistakes in the ins file (are you sure your HKLF is correct), wrong
formatting of the hkl colums...  those are the more brain-dead ones, try
the shelx FAQ. 

phx.


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