Unless you are confident that twin exists you should not use twin refinement 
(Occam’s razor)



> On 5 Apr 2024, at 17:24, venkatareddy dadireddy <[email protected]> wrote:
> 
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> --
> 
> Hi Kay and Garib,
> 
> Thank you for your input.
> It is actually the twin refinement that gave rise to resolution discrepancy.
> For what reason I don't remember that I have turned the twin refinement ON
> and the same job was cloned again and again. 
> With the twin refinement OFF, it gave rise to resolution present in the MTZ 
> (2.0 A).
> From Xtriage: the correlation between
> the intensities related by the twin law 1/2*h-3/2*k, -1/2*h-1/2*k,-l with an 
> estimated twin
> fraction of 0.10 is most likely due to an NCS axis parallel to the twin axis. 
> The statistics independent of twin laws show no twinning (more close to 
> untwinned than perfect twin).
> Please suggest to me on how I proceed with refinement (twin OFF or ON).
> 
> Thank you,
> Venkat
> 
>  
> 
>  
> 
> 
> 
> On Fri, Apr 5, 2024 at 1:00 AM Garib Murshudov <[email protected] 
> <mailto:[email protected]>> wrote:
> Did you use twin refinement (is it really twin if you used that). 
> If twin refinement was used then twin related intensities might have 
> different resolution, in case when your crystal are pseudomerohedral twinned. 
> 
> Regards
> Garib
> 
>> On 4 Apr 2024, at 18:40, venkatareddy dadireddy <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
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>> --
>> 
>> Hi Kay,
>> 
>> Thank you very much for your insights. 
>> Following are the cell parameters from mtz and pdb header.
>> MTZ: 117.8560   66.1700   70.9040   90.0000   91.4240   90.000
>> CRYST1  117.856   66.170   70.904  90.00  91.42  90.00 C 1 2 1
>> 
>> The only difference is in the 3rd decimal point.
>> 
>> 
>> Thank you,
>> Venkat
>> 
>> 
>> 
>> On Tue, Apr 2, 2024 at 10:10 PM Kay Diederichs 
>> <[email protected] <mailto:[email protected]>> 
>> wrote:
>> Hi Venkatareddy Dadireddy,
>> 
>> do the unit cell parameters of your MTZ file and PDB file agree exactly ?
>> 
>> Take for example a cell of (100,110,120,90,90,90) in the header of the MTZ 
>> file, 
>> and (97,110,120,90,90,90) in the CRYST1 line of the PDB file.
>> 
>> In this example, the (50,0,0) reflection would be at 2.0A resolution if 
>> using the cell from the MTZ file, 
>> but it would be at 1.94A resolution if calculating the resolution based on 
>> the cell from the PDB file.
>> 
>> So perhaps REFMAC5 takes the cell from the PDB file, and phenix.refine takes 
>> the cell from the MTZ?
>> I didn't check but it may be worth finding out. 
>> 
>> HTH,
>> Kay
>> 
>> 
>> On Tue, 2 Apr 2024 21:16:57 +0530, venkatareddy dadireddy 
>> <[email protected] <mailto:[email protected]>> wrote:
>> 
>> >Hi,
>> >
>> >The resolution range in my MTZ file is 70.88 - 2.0 A. When I refined my
>> >structure using REFMAC5, the resolution that it gives is 70.88 - 1.94 A,
>> >the difference of 0.04 A. I also used Phenix.refine which gives the
>> >resolution output as it is in the MTZ file. Again, EDS (validation report)
>> >gives the right resolution. What could be the possible reason for this
>> >discrepancy? I have the structure deposited in the Protein Data Bank and it
>> >is on hold. Thank you in advance for your help.
>> >
>> >Thank you,
>> >
>> >
>> >
>> >
>> >
>> >
>> >*Venkatareddy Dadireddy,B1-10,Prof. S. Ramakumar's Lab,Dept. of
>> >Physics,IISc, Banglore.Cell: 07259492227*
>> >
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>> -- 
>> Venkatareddy Dadireddy,
>> B1-10,
>> Prof. S. Ramakumar's Lab,
>> Dept. of Physics,
>> IISc, Banglore.
>> Cell: 07259492227
>> 
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> 
> -- 
> Venkatareddy Dadireddy,
> B1-10,
> Prof. S. Ramakumar's Lab,
> Dept. of Physics,
> IISc, Banglore.
> Cell: 07259492227
> 
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