Can you use sftools to get two ranges eg:  select reso   >3.85   and > 3.75

Eleanor

On Thu, 4 Apr 2019 at 11:39, Frank von Delft <frank.vonde...@sgc.ox.ac.uk>
wrote:

> You can use sftools to set a shell of reflections to MNF - then Refmac
> will fill those in with DFc, and that'll presumably be much better than
> having very wrong reflections.
>
> Whether that will fix your Rfactor is a different story.
>
> phx
>
>
> On 04/04/2019 11:05, Eleanor Dodson wrote:
>
> You cant exclude one resolution ring in REFMAC - there would be ways to
> fudge the exclusion from your current file, but much safer to use a data
> integration tool
>
> On Thu, 4 Apr 2019 at 10:27, <herman.schreu...@sanofi.com> wrote:
>
>> Dear Sam,
>>
>>
>>
>> I would remove the ice ring and reprocess the data. Ice rings may wreak
>> havoc with scaling so at minimum you have to redo the scaling.
>>
>>
>>
>> Best,
>>
>> Herman
>>
>>
>>
>> *Von:* CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] *Im Auftrag
>> von *Sam Tang
>> *Gesendet:* Donnerstag, 4. April 2019 11:01
>> *An:* CCP4BB@JISCMAIL.AC.UK
>> *Betreff:* [EXTERNAL] Re: [ccp4bb] High Rfree - ice ring
>>
>>
>>
>>
>> Dear Eleanor and Eric
>>
>>
>>
>> Thanks for your replies.
>>
>>
>>
>> Yes indeed when we looked at the plots e.g. R factor vs resln there was a
>> sharp peak near 3.6 - 3.8 A which is where we visibly saw an ice ring on
>> the image. Thus our first thought was to remove the ic ring. (either
>> reprocess or can we bypass this resolution range during refinement?)
>>
>>
>>
>> The protein is 50 kDa, two molecule in the ASU, seemingly no obvious
>> density was unassigned. We got ~30000 total observations, ~15000 unique
>> observations. NCS restraints was applied.
>>
>>
>>
>> Best regards
>>
>> Sam
>>
>>
>>
>>
>>
>>
>>
>> On Thu, 4 Apr 2019 at 08:57, Eric Montemayor <montemayor.e...@gmail.com>
>> wrote:
>>
>> That’s a rather large gap between Rwork and Rfree.  I suspect you have
>> mis-assigned your space group and as a result have a large number of copies
>> in your asymmetric unit.  Any structure can be solved in P1, but that does
>> not mean the true space group is indeed P1. If you use P1 when it’s not
>> actually P1, you will have an unnecessarily overparamerized model, hence
>> the large gap between Rwork and Rfree.
>>
>>
>>
>> Questions:
>>
>> 1- how many copies in your asymmetric unit in P1?
>>
>> 2- how many atoms in your model vs number of unique reflections?
>>
>> 3- if more than one copy per asymmetric unit, are you imposing NCS
>> restraints during refinement?
>>
>>
>>
>> -Eric
>>
>>
>>
>>
>>
>>
>>
>> On Wed, Apr 3, 2019 at 1:41 PM Sam Tang <samtys0...@gmail.com> wrote:
>>
>> Hi everyone again
>>
>>
>>
>> Hmmm I think we have solved a structure in P1 space, to 2.5 A. However
>> after refinement the Rfree stuck at 33%-35% with Rwork around 26%. The
>> structure was solved by MR and current model seems to fit density well. In
>> Refmac log I found that at the resolution corresponding to high R there may
>> be a solvent/ice ring. Since imosflm should be able to exclude ice rings, I
>> am not 100% sure whether it's the cause to high R. But if this is actually
>> the case, is there a way I can exclude certain resolution bins during
>> Refmac (and is it an appropriate way to do so?)
>>
>>
>>
>> PS - the data is not affected by twining or pseudosymmetry as checked by
>> Xtriage.
>>
>>
>>
>> Many thanks!
>>
>>
>>
>> Sam
>>
>>
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