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Hi Nicola, I would just add zinc solution to the protein before the crystallization and/or to the drop with crystals. An important thing to keep in mind is that Zn salt solutions will have low pH, unless a sufficient buffer is used. I recommend having a look at the article "Characterizing metal-binding sites in proteins with X-ray crystallography" https://www.ncbi.nlm.nih.gov/pubmed/29674755 With best regards, Ivan Shabalin, Ph.D. Research Scientist, Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Pinn Hall,Room 4223, Charlottesville, VA 22908 https://www.linkedin.com/in/shabalinig/ https://minorlab.org/person/ivan_s/ On 12/9/18 16:31, Nicola Evans wrote: > From a fluorescence scan it would appear a protein I am working on has zinc in it. The occupancy is likely to be very low however (a structural homologue has several zincs in the x-ray crystal data but at 0.5 occupancy), as there isn't anything obvious in the electron density map (perhaps some of the waters are zinc) and an anomalous difference map wasn't possible to obtain on our last beamtime. > > Ideally I would want to re-express the protein with zinc added to the culture conditions, but I am time-restained, so I was wondering if it is possible to add zinc to purified protein instead? I have heard it can cause proteins to crash out. I have quite a lot of protein frozen so I can try a few things. I would appreciate any advice on how much to add from anyone who has had success with this before? > > Thanks in advance! > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 > ---- ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1