Dear Andy, I few thoughts from my side, but no solution I am afraid:
* Your twinning operator -h, -k, l is the standard alternative indexing for P3x space group, which makes a lot of sense. * P32 is a low symmetry space group, which makes MR easier, but this is offset by the NCS. * In my hands, MR is surprisingly insensitive to twinning, so I would search for the molecules using the twinned data. Also, for MR one does not need extremely high resolution data. * However, twinning and low resolution data seriously hamper "de novo" model building. So if you have good MR models for your d1 and d2 domains, you may have a good chance of solving the structure. If you would have to build them "de novo" in a MR electron density map, you may be doomed. * What I would do, is to look at the phaser map using a very large map radius: say 35-40 Å or more and look in the solvent region if there are places with higher density that may suggest the presence of the missing domains. If something shows up, you can focus on those regions in your MR, or even try to manually fit the Ca chain of your MR model. * You certainly have already done it, but Phaser has to option to search for additional domains, given the domains you already found. Best, Herman Von: CCP4 bulletin board <[email protected]> Im Auftrag von Andrew Lovering Gesendet: Montag, 14. September 2020 11:17 An: [email protected] Betreff: [EXTERNAL] Re: [ccp4bb] Best protocols to advance a low resolution twin EXTERNAL : Real sender is [email protected]<mailto:[email protected]> To follow on from this thread: To answer Jon, I did try to see if P6 subgroups were a possibility but can rule this out for a few reasons (MR doesn't give solutions, merging stats not suggestive of P6, the other dataset with the twin fraction that is significantly further from 50:50); and the d3:d3 NCS is not parallel to any crystallographic axis The spacegroup is indeed P3 sub 2, not P321, and the solution again only possible in P3 sub 2 not P3 sub 1, so spacegroup confidence is high I did get one reply from Petrus Zwart that twin refinement / map improvement is a subject being worked on What I might try is a Phaser MR where the "missing domains" are searched for using cut out density of the one placed domain, rather than model (which could possibly be a better choice at this low resolution? Thoughts appreciated) Best wishes & thanks everyone Andy ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1<https://urldefense.proofpoint.com/v2/url?u=https-3A__www.jiscmail.ac.uk_cgi-2Dbin_WA-2DJISC.exe-3FSUBED1-3DCCP4BB-26A-3D1&d=DwMFAg&c=Dbf9zoswcQ-CRvvI7VX5j3HvibIuT3ZiarcKl5qtMPo&r=HK-CY_tL8CLLA93vdywyu3qI70R4H8oHzZyRHMQu1AQ&m=KZqf_b9f5DDNSrRRmROn70ilu9Dyk7cLAM5ZnYPTQvw&s=T4-pnYsjWTxcOlYa29UKmFqHN9wpMt_6nLo8YJySmAI&e=> ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
