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Re: [ccp4bb]: Solvent Flattened Data



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Thanks for the reply. To address your points:

1) By flattening the data, I mean taking the phased output and modifying the
phases using the Wang or Leslie method. Missing reflections are filled in.
I regard phases as data (though I can see arguments against this).

2) I have used RESOLVE for flipping, which is supposed to give realistic
FOM's. So I don't thing that is the problem.

3) I used HL coefficients of the flattened data for refinement (which
appeared to run quite well, as judeged by FOM and Rfree) and calulating maps
(which is where the problem pops up). PHIC and SIGMAA weights are inculded in
map calculations.

I still have no idea what could be cauing the problem.

Many thanks

AGS

"Eleanor J. Dodson" wrote:

> Paul Hubbard wrote:
> >
> > ***  For details on how to be removed from this list visit the  ***
> > ***          CCP4 home page http://www.ccp4.ac.uk         ***
> >
> > Hello all,
> >
> > I am having trouble using SIGMAA on solvent flattened data, and I can't
> > figure out why.
> >
> > I have a reasonable model which is about 70% complete, built using
> > solvent flattened experimental data to 3.7 Angstroms (no phase
> > extension). However when I use this data with the model in SIGMAA, the
> > map looks awful. However, when I use the un-flattened data things look
> > peachy. I tried swapping FP's with the native data, but no improvement.
> > Am I missing something here?
> >
> > By the way, just out of curiosity, would it be okay to use FWT and PHFWT
> > (WCMB) for solvent flattening? Supposedly this is an unbiased 2Fo-Fc, so
> > I would suspect flattening would tidy things up. Just wondering.
> >
> > Thanks
> >
> > AGS
> >
>
>  I am not quite clear what you mean - I dont think you "solvent flatten"
> data - it is a technique to improve phases - the data stays the same..
>
> Two points:
> We find that solvent flattening can often over estimate the FOMs and
> that you need to use HL copefficients with SAD data..
>
>
> If you have a model and exptl  phases before or after dens. modification
> you can get combined FOMS from Refmac5 too.
>
>  Eleanor

--
Paul Hubbard
Dept. of Biochemistry
Medical College of Wisconsin
Phone: 414-456 4305
Fax: 414-456 6510
URL: iris9.biochem.mcw.edu