<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body >Magnesium has fewer electrons. So if you place it and it's actually calcium you should see extra density and the B-factor will be unreasonably lower than surrounding atoms.<div><br></div><div>Distances are less reliable at intermediate resolutions as they are largely controlled by restraints. Maybe.</div><div><br></div><div>Assuming that you have 100% occupancy.</div><br><br><br>-------- Original message --------<br>From: Daniel Slade <DSlade@scripps.edu> <br>Date: <br>To: phenixbb@phenix-online.org <br>Subject: [phenixbb] Magnesium or calcium <br> <br><br>I have several structures that has multiple known calcium binding sites, and I found a new site that seems to accept calcium or magnesium. I say this because if a magnesium is put in the structure, the bond lengths are ~ 2.1. But if you put a calcium in it, they go to ~2.6. All of these refinements were done without ReadySet, which I recently used with metal restraints and it seemed to change the bond length of calcium to ~2.4. I'm a bit confused as to what to do here as either metal seems to be right. Worth noting, this is a very strong metal binding site that can't be removed with 10 mM EDTA.<br><br>Any help here on how to figure this out which ion this is would be great.<br><br>Thanks in advance<br><br>Dan<br><br><br>_______________________________________________<br>phenixbb mailing list<br>phenixbb@phenix-online.org<br>http://phenix-online.org/mailman/listinfo/phenixbb<br></body>