Re: [ccp4bb]: Re:Problems with low mosaicity

[Timm Maier <tmaier@chemie.fu-berlin.de>]

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We have observed high Rsym ( 10 % ) together with low I/sigI ( 5 ) in the
low resolution shells as reported here with data from ID29 when using
standard parameters for mosflm processing. 
For our data clearly the problem is that the automatic measurement box
refinement in mosflm does not work properly if very large spots are
present in the low resolution shells together with small spots in higher
resolution shells. Turning off the measurement box refinement and
setting the box to a larger value manually yielded data of reasonable 
quality ( Rsym 3.5 % , I/sigI 15 for lowest resolution shell). By the
way, also increasing the mosaicity estimate by hand improved data quality
significantly. 
Probably many people are using mosflm for ID29 data processing (
maybe for the first time ) because they don't have a HKL license for Q210
detector yet, so some of the problems reported may be due to
this or similar processing software problems. These problems are also
especially likely to occur on such a high brilliance beamline ( thanks to
ID29 staff !!! ) , that gives you extremely intense spots even when using
attenuators and 1sec exposure times !  

Bye TIMM    

On Thu, 7 Mar 2002, J. J. Müller wrote:

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> 
> Hallo,
> really an interesting point. Astonishing is, that the most people
> measured at ID29 in Grenoble in the last period.
> We measured also two datasets of different proteins with Rsym=11% in the
> inner shell and 15% in the outer what we have not seen before. The
> mosaicity is quite normal. So, one should ask the beamline people what
> is going on there?
> Juergen
> 
> 

____________________________________________________________________________

                 TIMM MAIER
                           Proteinkristallographie
                           Institut fuer Kristallographie
                           Takustr.6
                           14195 Berlin

                           tmaier@chemie.fu-berlin.de                   
____________________________________________________________________________