Hi Nicola, If all you are looking for is evidence that you have zinc in your structure based on the anomalous difference map, then with the data you already have you should be able to calculate the anomalous difference map! All you have to do is to reprocess the data in anomalous mode or whatever your favourite data processing software calls it. That will process the data with Friedel mates kept separate and you can get anomalous differences from them. If you have collected the data away from the absorption edge of zinc you should still be able to get anomalous differences though they might be small.
What wavelength was used for the data collection? HTH Raghu -----Original Message----- From: CCP4 bulletin board <[email protected]> On Behalf Of Nicola Evans Sent: Monday, December 10, 2018 03:02 To: [email protected] Subject: [ccp4bb] Adding Zinc to Protein 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
