Hi Mary, I have not tried the phenix multi-crystal averaging procedure with twinned data, but here are some suggestions of how to proceed. 1. This routine does not do any refinement, only density modification. The density modification step does not know about twinning, so it will be necessary (if your data are significantly twinned) to supply structure factor files with detwinned data. I will check with Peter Zwart on producing detwinned data in phenix; it may be necessary to do that with other tools as normally phenix.refine uses the original data and does the calculations internally. 2. The models you supply are used to (a) identify NCS symmetry and cross-crystal symmetry. Therefore it should not really matter if these models are incomplete, and therefore the approach you are using should work for improving the region where you have no model. The region where NCS is applied is defined as a region centered near the center-of-mass of the supplied model over which the NCS correlation is high. I hope that helps! All the best, Tom T I started running this function and then realized that I probably need to do something to take the perfect twinning into account. I'm not sure of the best way to do this. I believe the map coefficients output by a run phenix.refine should be detwinned as I give a twin law when running phenix.refine. Should I detwin the mtz containing the data and then use those files for the multi crystal averaging? Is there a way to output detwinned data mtz files in phenix or do I need to use another program? Also, I have two ncs copies in the ASU. There's a region of density in both ncs copies that I'm trying to improve the maps for with the multi crystal averaging. I don't have anything built in the region yet. Is there a way to use the NCS and multi crystal averaging at the same time without any pdb coordinates in that region? Even with my goof up about the twinning, the eff script I created appeared to run without problems. Thanks, Mary X. Fitzgerald Postdoctoral Associate Arnold Lab _______________________________________________ phenixbb mailing list [email protected] http://www.phenix-online.org/mailman/listinfo/phenixbb