Hi Yangqi, There was a bug in mtriage in a few versions that did lead to this behavior of the FSC not being 1 at low-res. You could try a nightly build and see if this is the cause (or perhaps it really should be lower but that is not likely). In principle at least you should be able to use the helical symmetry for creation of a complete model from a protomer (if that is what you are asking) You can try phenix.map_symmetry and see if that finds the NCS. Otherwise, you can input your NCS with helical symmetry to phenix.map_symmetry and it should check that ncs. The most likely problem is if the helical axis is not along (0,0,1). Let me know if that doesn't work, All the best, Tom T On Wed, Dec 11, 2019 at 2:04 PM Yangqi Gu wrote:

Dear Phenix developer, I have a question regarding the map to model fsc. I have a filament map and a model with arbitrary copy of the protomer ( I built them in Chimera), then I used the filament model to refine against my map. But I encountered an issue is that the reported FSC (map to model) did not start from 1 but rather 0.8. I am wondering if there is anyway to fix it. Also, in the case of a filament, how do I use NCS operator to refine rather than manual building the filament model? I tried specifying NCS with helical symmetry, but it did not work. Best, Yangqi

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-- Thomas C Terwilliger Laboratory Fellow, Los Alamos National Laboratory Senior Scientist, New Mexico Consortium 100 Entrada Dr, Los Alamos, NM 87544 Email: [email protected] Tel: 505-431-0010