Hi Jiang Xu, (Phenixbb added as I suspect this is Phenix not coot that has caused your issue) Did you check the "add hydrogens" button in Phenix.refine? Sometimes this can erroneously add a second H to the ND of glycosylated Asn residues. (I assume this is because bond distances in the input PDB file fall outside Phenix's definitions of an Asn-NAG link). If the second H is added, this breaks the refinement of the Asn-NAG bond. My work around is to run "Ready Set" to add hydrogens as a separate job, and then manually inspect and correct the Asn residues as necessary before running Phenix.refine and _not_ checking the "add hydrogens" box. I hope this fixes your problem. Good luck, Dave -- Dr David C. Briggs Senior Laboratory Research Scientist Signalling and Structural Biology Lab The Francis Crick Institute London, UK == about.me/david_briggs ________________________________ From: CCP4 bulletin board on behalf of Jiang Xu Sent: Tuesday, June 22, 2021 6:47:36 AM To: [email protected] Subject: [ccp4bb] missing covalent bond between asparagine and N-acetylglucosamine using coot carbohydrate module and phenix.refine External Sender: Use caution. Hello guys, I have a problem building and refining an xtal structure. My protein has a N-glycosylation site and I want to add N-acetylglucosamine and manose to my protein structure. I used Coot's carbohydrate module and let Coot automatically build the sugar chain to the electron density. It worked pretty well, but I noticed that the bond between the amine group of asparagine and the C1 of N-acetylglucosamine is depicted as a dashed line, rather than a solid line in Coot. After refinement of the structure using Phenix.refine, I found the bond just disappeared, and the amine group still has two hydrogen atoms, which should contain one hydrogen atom. So, how to solve this problem? [image.png] Thank you, Best, Jiang Xu Lin Chen's Research Group University of Southern California ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.jiscmail.ac.uk%2Fcgi-bin%2FWA-JISC.exe%3FSUBED1%3DCCP4BB%26A%3D1&data=04%7C01%7C%7C48beee7b9a244fc683ba08d93542c46d%7C4eed7807ebad415aa7a99170947f4eae%7C0%7C1%7C637599383149545061%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=QP5gUcvAYN43BkYOgqf9ynTIgA0mEmEGxXRmfsQi86s%3D&reserved=0 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 1 Midland Road London NW1 1AT