Re: [ccp4bb]: stuck R and arp and refmac problems

[Aaron Oakley <aoakley@receptor.pharm.uwa.edu.au>]

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> I'm having a problem where my R and R free are stuck at 28 and 26% at
> 1.92A resolution and there doesn't seem to be anything wrong with the
> model.
> 

I had a case like this recently where the root cause was
a breakdown in xtallographic symmetry....The actual
symmetry was P4(3) but was pseudo P4(3)2(1)2, with
excellent merging statistics in both groups.

The problem here is that by lowering the symmetry you
are increasing the no. of parameters you are refining,
so you will always lower R this way even if symmetry is
not the problem. You have to be careful!

Aaron