[phenixbb] PHASER-TFZ scores with ensembles higher?

[Gabor Bunkoczi]

Dear Jan,

I leave the it for the more knowledgeable to answer your question about the 
effect of ensembles on TFZ. It is, however, not uncommon that a solution 
with an ensemble is difficult to refine (at least with a single model), 
esp. when none of the ensemble members are good models (which you have 
verified). In this case, you may get better results by building a "chimera" 
model (recombining parts of the ensembles that match the electron density 
best) and use that one for refinement. We have implemented an automatic 
procedure for phaser.MRage output using Tom Terwilliger's 
phenix.combine_models program, and this could be modified to work with 
Phaser output as well. Let me know if this were potentially useful for you 
now.

BW, Gabor

On Jun 28 2013, Jan Gebauer wrote:

>Dear Phaser users,
>
>I recently tried to solve two difficult MR jobs by using ensembles in  
>PHASER.
>With ENSEMBLES in this case I mean aligned structures prepared for PHASER  
>by Phenix.ENSEMBLER.
>In both case I got solution with rather high TFZ-score (> 8), which I  
>couldn't get wit individual structure, but was not able to refine them.
>
> My question is, whether using ensembles would increase the Z-Score 
> without really improving phases. In other words, if there is another 
> cut-off for the "Phaser solved it" Z-score, when using ensemble in 
> contrast to single structures...
>
>Regards,
>Jan
>

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     Dr Gabor Bunkoczi

     Cambridge Institute for Medical Research
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