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Hi Seema, In theory, Ammonium Sulfate contains some small fraction of neutral ammonia which can act as a strong nucleophile and react with many heavy metal compounds. That being said, I recently phased two structures with mercury soaks, both of which contained ammonium sulfate. The first was a thimerisol soak with 2M AmSO4 in the mother liquor, and the second with a MeHgCl soak with 0.2M AmSO4. Both were fairly routine. I think others will agree that with heavy metals, logic and theory can go right out the window. There is no way of knowing if it will work, you just have to try. One tip I can offer is to use fresh stocks of metals dissolved at saturating concentrations in water and used on the same day. The fresher the better in my experience, but it could just be voodoo. Good luck! --Paul --- On Sun, 9/26/10, Seema Nath <[log in to unmask]> wrote: > From: Seema Nath <[log in to unmask]> > Subject: [ccp4bb] problem in heavy metal soaking > To: [log in to unmask] > Date: Sunday, September 26, 2010, 9:00 AM > I'm working with a protein which > crystallizes in a mixture of PEG6K with 0.2M AmSO4,my > question is if there's any problem if I want to soak heavy > metal derivatives in this crystallizing condition? Does > AmSO4 interfere in heavy-metal soaking ? if yes, what's the > reason? > Thank you in advance. > >