Could you expand a bit on what you mean by a “putative” systematic absence? 
(e.g. why only the lowest order hkl?)



On 5 Apr 2018, at 19:39, James Holton 
<jmhol...@slac.stanford.edu<mailto:jmhol...@slac.stanford.edu>> wrote:


You need to be careful with the exact space group at the particular stage in 
your pipeline here.  Often the lowest-order hkl is a putative systematic 
absence, so if you uniqueify in P222 you will get it, but if you uniqueify in 
P212121, then you won't.  That sort of thing.  Note that it doesn't matter what 
the "true" space group is, it only matters what is in the mtz header when you 
run uniqueify.

Could that be what is going on?

-James Holton

MAD Scisntist

On 4/5/2018 3:52 AM, Frank von Delft wrote:

Hello - can anybody shed light on this mystery:

We need (for PanDDA analysis) a lot of datasets each to have the complete set 
of low resolution indices, whether measured or not.  (Refmac adds the estimates 
as DFc, which is crucial when comparing maps.)

In ccp4, there are two obvious ways to get these indices complete:

  *   uniqueify
  *   CAD using the keyword "RESOLUTION FILE 1 999 <highres>"  (999 is the low 
resolution limit).

Mystifyingly, in ~1% of datasets, one or the other route misses one or two 
indices.  Our work-around is to go belt-and-braces and run both for each 
dataset.


It does however remain a bug.  Does anybody have any idea what's happening?  We 
can send example datasets to any volunteers who want to fiddle with it.

phx



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