Hi Gino, I have never tried any problem of this size...but here is a way to proceed using Randy's "input_partpdb_file" option for Phaser that is now available in the autosol wizard. Take your EM model with all its NCS copies, and give it to AutoSol with the keywords: input_partpdb_file=MR.pdb partpdb_rms= 3.0 The partpdb_rms should be the estimated RMSD between the MR model and the true model. You will have as good an idea about this as anyone... You also would supply the usual information to autosol: phenix.autosol sad-data.sca seq.dat 450 Se f_prime=-8 f_double_prime=4.5 \ build=False input_partpdb_file=MR.pdb\ partpdb_rms=3.0 \ resolution=6.0 You might cut the resolution to a pretty low value like 6 A as above. If you get a lot of good sites refined by phaser, then you may be on the right track. This autosol run will output phaser_1.mtz and also resolve_1.mtz that you can use as a starting point for further density modification and model-building as appropriate. Given the size of this problem, I would anticipate lots of challenges, and we will be happy to help as you carry on with it. You might try running everything at really low resolution (20A) at first just to get things to run... All the best, Tom T Hi Phenix community, I was wondering if Phenix can handle MR starting from medium/low res EM models. I have a very large oligomeric protein (2.4MDa) with lots of NCS and >450 Se-Mets. In principle, I could use low res MR phases from the "replaced" model to locate Se-sites and then NCS-averaging to locate more sites and improve my phases. Any suggestions how to get Phenix to use an EM model? Has anybody done it successfully using Phenix? Thanks in advance, Gino *********************************************************** Gino Cingolani, Ph.D. Assistant Professor Dept. of Biochemistry and Molecular Biology SUNY Upstate Medical University 750 E. Adams Street, Syracuse, NY, 13210 Tel. (315) 464 8744 Fax. (315) 464 8750 Email: [email protected] *********************************************************** "Nati non foste per viver come bruti, ma per seguir virtute e conoscenza" ("You were not born to live like brutes, but to follow virtue and knowledge") Dante, The Divine Comedy (Inferno, XXVI, vv. 119-120) _______________________________________________ phenixbb mailing list [email protected] http://www.phenix-online.org/mailman/listinfo/phenixbb