Under what criteria would one embark on using multi-xtal averaging?
-Same unit cell / s.g. (isomorphism)
-Data was collected from xtals from different conditions?
-MR model shows different/unrecognizable features in 2Fo-Fc maps for each xtal individually?
-What if some residues are dynamic (different orientations in each xtal) or disordered? Would these show up garbage or not at all in the averaged map?
Any *good* (i.e. well detailed) papers discussing the details of multi-xtal averaging would be great.
Tom: Are only model phases used? In other words, are/can experimental phases used? Would having experimental phases from any of the xtals help in cases where the current model is incomplete (say 60%/70% built or Rfree in the 30's) ?
On Jun 26, 2009, at 7:39 AM, Tom Terwilliger wrote:
Hi Frank,
I have not done this with twinned data....but I would say yes, detwin everything for this step if you can (but of course refine against the twinned data with a twin target). It is probably good to detwin because the density modification procedure does not know about twinning...
All the best,
Tom T
On Jun 26, 2009, at 1:18 AM, Frank von Delft wrote:
Hi Tom,
Yep, that I figured out, but do I need to detwin the native F's first?
Cheers
phx
Tom Terwilliger wrote:
Hi Frank,
To use phenix.multi_crystal_average you need one more step: take the
model from your SeMet dataset and do MR on it in the native cell with
native F. Now you have the correspondence between the two cells, and
you can plug the 2 models and the one phase set and the native F's
straight into phenix.multi_crystal_average to transfer the phase
information to the native (and cross-crystal average).
All the best,
Tom T
On Jun 23, 2009, at 1:44 AM, Frank von Delft wrote:
Hi, I'm trying to to figure out how to transfer phases from a twinned
SeMet dataset to the native one for refinement.
1) SeMet dataset (2.9A) is solved (despite twinning), structure built,
refines 29/35 (ish)
2) SeMet crystals are hemihedrally twinned (confirmed by refining with
twin law), native probably too.
3) Native dataset (2.7A) has 5A difference in the long cell edge (478 vs
483A).
So I could (and will try to) simply copy the SeMet phases into the
native dataset, even though CC Fnat and Fsme is rather low (80-20%).
But would phenix.multi_crystal_average know what to do with this? It
has no explicit options, so I expected not.
Or how *would* one approach this?
Cheers
Frank
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