Hi, We recently solved a structure where two citrate molecules from the crystallisation condition are bound to the protein. They are nicely defined in the electron density. There is some difference density between the two citrates that looks like a water molecule: https://www.dropbox.com/s/9hxyty5f7udlk6q/Screenshot%202021-02-26%20at%2010.43.13.png?dl=0
So, we have built a water molecule into the difference density. The “water” has a roughly tetrahedral coordination sphere with two H-bond donors and two H-bond acceptors around it, but the distances are too short (around 1.8 Å): https://www.dropbox.com/s/5pgxlvt72hngjty/Screenshot%202021-02-26%20at%2010.38.44.png?dl=0 https://www.dropbox.com/s/mcqteu5ibu265lo/Screenshot%202021-02-26%20at%2010.41.22.png?dl=0 We have thought about sodium ions. But looking at citrate structures in the CSD, I found that the distances are also too short for sodium. If anybody has an idea what might sit between these two citrate molecules, please let me know! I am of course happy to give any further information. Cheers, Gregor ----- PD Dr. Gregor Hagelueken Institute of Structural Biology Biomedical Center (BMZ) Building 13, Rm 2G 022/023 University of Bonn Venusberg Campus 1 53127 Bonn, Germany Phone: +49 228 287-51200 WWW: http://www.isb.uni-bonn.de/ ----- ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
