[phenixbb] Troublesome molecular replacement

Nathaniel Echols nechols at lbl.gov
Mon Oct 29 13:30:12 PDT 2012

On Mon, Oct 29, 2012 at 1:16 PM, Yuri <yuri.pompeu at ufl.edu> wrote:
> I recently collected on a crystal that diffracted pretty well to 2.0 A.
> It indexes and scales fairly well in P 4 21 2 with cell dimensions 100, 100,
> 200.
> This would predict 4 molecules/ASU.
> I found a MR solution in P 41 21 2 but it does not refine very well Rfree
> =42%.
> Xtriage detects strong peaks at 0,0,0.25 for Translational NCS.
> Any suggestions on how to go about this one?

Just a few simple thoughts:

1) Are you certain about the space group, and did you try letting
Phaser pick one for you?  (It sounds like you did, but I can't tell
from your description.)

2) How much refinement did you run to get an R-free of 42$, and did
you already try running AutoBuild with rebuild-in-place turned off?
Refinement alone may not have the radius of convergence you need.

3) What is the sequence identity?

4) Are you using the latest version of Phenix?  Phaser has had TNCS
support for almost a year now but I keep hearing from people who are
using ancient versions...


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