Dear Fulvio, We just had a similar problem (further complicated by some twinning). Assuming that: 1. You collected enough data and 2. You don't have a crazy number of molecules in the tetragonal asymmetric unit, I would advice to scale your data in P1 and do MR in P1. Then use conventional refinement + model building to bootstrap a better model (most likely your initial model isn't as good). Rosetta may help, too. Then eventually go back to the tetragonal data with the improved search model and see if LLG and packing make sense. Gino **************************************************************** Gino Cingolani, Ph.D. Associate Professor Thomas Jefferson University Dept. of Biochemistry & Molecular Biology 233 South 10th Street - Room 826 Philadelphia PA 19107 Office (215) 503 4573 Lab    (215) 503 4595 Fax    (215) 923 2117 E-mail:   [email protected] Website:  http://www.cingolanilab.org **************************************************************** "Nati non foste per viver come bruti, ma per seguir virtute e  canoscenza" ("You were not born to live like brutes, but to follow virtue and  knowledge") Dante, The Divine Comedy (Inferno,  XXVI, vv. 119-120) Fulvio Saccoccia wrote:

Dear phenixbb, I have a data set collected at 2.2A resolution that I can integrate in P4. Aimless, Phaser and Xtriage recognized a pseudotranslation (34.6% of origin peak) at fractional coordinates 0.500 0.500 0.479 (ORTH 46.7 46.7 37.4). However labelit.index run with sublattice_allow=true search did not detect the pseudotranslation vector. So far, any attempts to phase by molecular replacement was unsuccesfull and I suspect that it could be due to incorrect assignement of space group:

Now, some questions arise: 1) does the pseudo translation exist or do not? 2) if translational NCS is present, could it mimic a P41/P42/P43 space group? 3) in any case, any advices in order to properly deal with tNCS will be of great help?

I thank you in advance Best wishes

-- Fulvio Saccoccia, PhD Sapienza University of Rome Dept. of Biochemical Sciences "A. Rossi Fanelli" Piazzale Aldo Moro, 5 00185 Rome (Italy)

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