Re: [ccp4bb]: TLS refinement: Fix B-factors?

[Garib N Murshudov <garib@ysbl.york.ac.uk>]

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Refmac does not fix B values. It sets initial value to whatever you give and 
then refines from that point. If you don't use individual atomic B value 
refinement then all B values will be equal not necessarily to that given by 
user.  If you use individual B refinement then program will refine TLS and 
then residual B values. Check if you are using individual B refinement after 
TLS. That may make difference. 


Garib
On Thursday 10 October 2002 11:09, Florian Schmitzberger wrote:
> Dear all,
>
> I am refining a structure with two protomers in the asymmetric unit;
> resolution range 25-2.0 Angstroem; hexagonal space group P6122; total
> number of reflections: 22 000; total number of atoms to refine: ~2800.
>
> I have been using TLS refinement in the last stage of refinement and got a
> nice drop in Rfree and Rcryst: before TLS: Rfree=19.3 Rcryst=17.3. after
> TLS refinement: Rfree=18.2 Rcryst=16.6. I used two TLS groups for the two
> protomers in the asymmetic unit respectively, 5 cycles of TLS refinement+9
> cycles of normal Refmac refinement. However I did not turn the "Fix
> B-factors" field on, though I entered Wilson B in the respective field.
> When going back and runnning the same refinement procedure as above, this
> time fixing B-factors to Wilson B I get: Rfree=18.5 Rcryst= 17.3. i.e
> little worse than above.
>
> Since I am not very experienced in using TLS refinement my question is
> whether it is necessary to fix the B-factors. It makes more sense to me,
> but I would like to have some competent advice on that. If fixing is
> advicable: to what should I fix it  (with this particular refinement
> problem).
>
>
> Thanks very much,
>
> Florian
>
> -------------------------------------
> Florian Schmitzberger
> University of Cambridge
> Department of Biochemistry
> 80 Tennis Court Road
> CB2 1GA Cambridge
> Tel: 0044-1223-766029

-- 
Dr. Garib N Murshudov, YSBL, Chemistry Dp, Univerisyt of York
Tel: (01904) 328252