Hi William, For find_ncs_from_density the shape of the molecule itself is not so important. What matters is if there is some local part of the molecule that is recognizable in both copies. So I would try default parameters first. I assume you did that and it didn't give you a useful answer...so then I would do these things: 1. try many locations : n_center_use=20 This is the best option...it will try 20 times using density at 20 different locations to search. If you have an older version of phenix you may need to download a nightly build to do this. 2. Try varying the resolution 3. Try varying the angular spacing of the search (delta_phi) All the best, Tom T ________________________________ From: CCP4 bulletin board [[email protected]] on behalf of William Chao [[email protected]] Sent: Friday, July 03, 2015 10:24 AM To: [email protected] Subject: [ccp4bb] Optimal settings for finding NCS from density Dear all, What would be the best settings to look for NCS using phenix.find_ncs_from_density on an elongated (~150A) molecule? No coordinate is available unfortunately and there should be 2 copies in a P21 space group. Many thanks in advance! William --- The Francis Crick Institute Limited is a registered charity in England and Wales no. 1140062 and a company registered in England and Wales no. 06885462, with its registered office at 215 Euston Road, London NW1 2BE.