Hi Alex, Was it purified via a Ni2+ resin? Is the protein oligomeric in solution? Could it have stripped an ion out during purification and brought it all the way through to crystallisation?
Have you tried refining a Ni2+ in the location? JP -------------------------------------------------------------------------- AstraZeneca UK Limited is a company incorporated in England and Wales with registered number: 03674842 and a registered office at 2 Kingdom Street, London, W2 6BD. Confidentiality Notice: This message is private and may contain confidential, proprietary and legally privileged information. If you have received this message in error, please notify us and remove it from your system and note that you must not copy, distribute or take any action in reliance on it. Any unauthorised use or disclosure of the contents of this message is not permitted and may be unlawful. Disclaimer: Email messages may be subject to delays, interception, non-delivery and unauthorised alterations. Therefore, information expressed in this message is not given or endorsed by AstraZeneca UK Limited unless otherwise notified by an authorised representative independent of this message. No contractual relationship is created by this message by any person unless specifically indicated by agreement in writing other than email. Monitoring: AstraZeneca UK Limited may monitor email traffic data and content for the purposes of the prevention and detection of crime, ensuring the security of our computer systems and checking Compliance with our Code of Conduct and Policies. -----Original Message----- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Alex Singer Sent: 24 February 2011 00:35 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] strange density Hi -- I have a high resolution structure (1.6 A) where I'm ready to deposit except I have some very strange density, shown in the two pictures here -- sort of a sphere with a split cresent around it, falling between molecule A and B His 138 imidazole rings. The sphere is modeled as a Cl atom, more for "kicks" because resulting 2Fo-Fc maps still have considerable positive difference density throughout the sphere. There are 4 molecules in the AU, the imidazole ring of H138 in molecules C and D point into a solvent channel. Crystallization conditions are 0.2M Mg Chloride, 0.1M Bis-Tris pH6.5, 25% PEG3350, cocrystallized in 2.5mM Glycero-3Phosphocholine and cryoprotected by dipping in Paratone_N oil. Let me know what you're thoughts are and thank you for your help. Alex Singer -- Dr. Alex Singer C.H. Best Institute 112 College St. Room 70 University of Toronto Toronto, Canada, M5G 1L6 416-978-4033
