Hi Suraj,

It is strange that the P3 crystals do not produce a MR solution. Since they all 
came from the same crystallization condition, you may want to check that no 
proteolytic cleavage of your protein has taken place and that your crystals 
only contain a fragment of your protein. You may also want to check that at 
least one complete molecule would fit into the asymmetric unit of your P3 
crystals.
Your R and Rfree values for your C2 data set may be artificially low due to the 
detwinning procedure, but as Eleanor mentions, they are not bad.

What I would do in any case is to rebuild and refine the structure of your C2 
crystals as well as possible. In the worst case that could be the only 
structure you get, but there are worse things. Most crystals structures in the 
PDB have been solved from a single crystal form. You can then use your rebuilt 
and refined model to run again MR with your P3 data. Maybe you are lucky and 
get a solution this time.

Best,
Herman


Von: CCP4 bulletin board <[email protected]> Im Auftrag von Eleanor Dodson
Gesendet: Freitag, 11. Dezember 2020 15:37
An: [email protected]
Betreff: Re: [ccp4bb] Problem in finding a MR solution

Well - C2 is a sub cell for P3 so that isnt surprising, but a cell difference 
of 202 to 212 means it isnt isomorphous..
But an
Rw Rf/ of 26/31 isnt bad for such low resolution data?
Eleanor

On Fri, 11 Dec 2020 at 12:01, Suraj Kumar mandal 
<[email protected]<mailto:[email protected]>> wrote:
Dear Sir,

Yes, we have checked handedness also. We are using the same MR solution with 
other data.


With best regards
Suraj



On Fri, Dec 11, 2020 at 4:56 PM srajan kapoor 
<[email protected]<mailto:[email protected]>> wrote:
Have you checked for handedness to solve this problem?.
You can also try to use the structure that you have solved for molecular 
Replacement of the other crystals.
I have only two things in mind currently. I hope it will work for you.

On Fri, Dec 11, 2020, 4:48 PM Suraj Kumar mandal 
<[email protected]<mailto:[email protected]>> wrote:
Dear All,

We are trying to solve a structure of a protein, for which we have collected 
five different home source data at 3.2-3.5 Ang resolution. We are processing 
the data using iMOSFLM and the program suggests P3 (and related) space groups 
for all the data. We are able to get a solution with one data (twinned) in C2 
space group with Rw/Rf of 26/28%. However, the same solution can not be 
obtained using other four data. Interestingly, one of these four data is not 
twinned. The only common thing in these four data, I find, is that they are 
crystallized in the same crystallization condition, whereas, the data which 
gives solution is crystallized in another condition.

The template has 69% sequence identity with the target protein.

Any suggestion to troubleshoot this would be appreciated.

With best regards,
Suraj

--
Suraj Kr. Mandal
Research Scholar
Structural and Computational Biology Lab
Department of Biosciences and Bioengineering
Indian Institute of Technology (IIT), Guwahati
Guwahati, Assam 781039
Ph.: 09678244566
E.mail: [email protected]<mailto:[email protected]>
           [email protected]<mailto:[email protected]>

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--
Suraj Kr. Mandal
Research Scholar
Structural and Computational Biology Lab
Department of Biosciences and Bioengineering
Indian Institute of Technology (IIT), Guwahati
Guwahati, Assam 781039
Ph.: 09678244566
E.mail: [email protected]<mailto:[email protected]>
           [email protected]<mailto:[email protected]>

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