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Hi, What resolution is this at ? If resolution is high enough you may be able to see other subtle signs of this disorder - like dual positions of relevant metal-binding residues (although Cd vs Mg would be tough). You can also try and refine dependent partial occupancies in SHELX but this is still only an estimate. Essentially, besides doing AA or ICP-AA on a defined sample of the protein, your guess is about as accurate as anything. Artem ----- Original Message ----- From: Sara Elizabeth Cnudde <[EMAIL PROTECTED]> Date: Monday, March 20, 2006 12:03 pm Subject: [ccp4bb]: metal sites To: ccp4bb <[email protected]> > *** For details on how to be removed from this list visit the *** > *** CCP4 home page http://www.ccp4.ac.uk *** > > > > Hi, > > I have a structure that I'm refining that I believe has a metal > site in > which 50% of the time it's occupied by cadmium and the other 50% of > the time > this same site is occupied by magnesium. How can I really tell if > this is > true? If I put Mg in with 100% occupancy I see a lot of density > in my > fo-fc map contoured at 3 sigma indicating that this is incorrect. > However, > if I put in Cd with 50% occupancy I no longer see this density but > if the Cd > has 100% occupancy I see density in the fo-fc map contoured at -3 > sigma. > > Thanks, > > Sara >
