I know you mentioned trying buffer components, but it does look a lot like TRIS to me, maybe a different conformation than you’re modelling?
JPK +++++++++++++++++++++++++++++++++++++++++++++++++ Jacob Pearson Keller Research Scientist / Looger Lab HHMI Janelia Research Campus 19700 Helix Dr, Ashburn, VA 20147 Desk: (571)209-4000 x3159 Cell: (301)592-7004 +++++++++++++++++++++++++++++++++++++++++++++++++ The content of this email is confidential and intended for the recipient specified in message only. It is strictly forbidden to share any part of this message with any third party, without a written consent of the sender. If you received this message by mistake, please reply to this message and follow with its deletion, so that we can ensure such a mistake does not occur in the future. From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Daniel Garcia Sent: Sunday, May 13, 2018 8:40 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Electron density Dear all, I am currently refining a structure and found a intriguing electron density at the protein surface (pictures attached, the Fo-Fc map is contoured at >3.5 sigma). My first candidates were molecules from my protein prep or crystallisation buffer, but none of them seem to fit well. I can observe that the ligand is nearby the side chains of a tyrosine, a lysine, a threonine and a glutamate residue, and it is close to the carbonyl oxygens of the protein backbone of a nearby loop. The shape of this density is not pyramidal, but it is not planar either. Do you have any suggestions to solve this density based on your own experience? My crystallisation buffer contains tartrate, ammonium sulphate, and CHES, and my protein is in Tris buffer containing DTT and sodium chloride. Best regards, -- Mario
