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In one case, co-crystallization with heavy atom (Au) was one of the few approaches that worked. Not sure if you've also tried short soaks with Hg, Pt, Au. Helped for one of my former colleagues while long soaks messed things up. You have not mentioned if Selenomethionine derivatization has been tried. Someone recently pointed out a paper about double lanthanide binding tags (dLBT; 15-25 aa). I have no experience with these tags yet but might be worth a try. Silvaggi NR, Martin LJ, Schwalbe H, Imperiali B, Allen KN. Double-lanthanide-binding tags for macromolecular crystallographic structure determination. J Am Chem Soc. 2007 Jun 6;129(22):7114-20. Epub 2007 May 12. Hope that helps. Raji ---------Included Message---------- >Hello all, >I am struggling with getting the phases out for my protein. Heavyatom >database shows that only mercury and samarium have the binding motifs in it. > >Sodium iodide soak is killing the crystal even as less as 0.2 Molar >concentration for 30sec. >With Potassium iodide crystal is okay upto 0.75M for 1 & a half min but the >incorporation is not at relevent sites.(Iodide signal is not distinct and >is weak) >Hg & Au salts precipitate it. >With Pt signal is weak. >Somewhere I read that high salt causes problems for heavy atom to bind to >protein.My protein needs high salt for stability (750mM NaCl) > >Please help with some suggestion!! > > ---------End of Included Message----------