Hey Jacob, If you are looking for a specific example there are numerous carbonic anhydrase structures that were crystallized in ~2.8M ammonium sulfate that have no sulfate in the structure. Usually they have a ligand in the active site which displaces the only ordered sulfate molecule. I have found this to be the case with >1M concentrations of citrate and acetate as well. Unless there is a specific "binding site" to organize the molecule in regards to the protein it just loiters in the solvent that you are flattening anyways.
Just my two cents, Katherine --------------- Katherine Sippel, PhD Postdoctoral Associate Department of Biochemistry Baylor College of Medicine On Fri, Jun 3, 2011 at 4:22 PM, Jacob Keller <j-kell...@fsm.northwestern.edu > wrote: > Dear Crystallographers, > > is it possible not to observe density for any sulfate ions in > crystallizations done with molar-range sulfate concentrations? > Beguiles the mind, but I seem to be looking at such a structure... > > Jacob > > -- > ******************************************* > Jacob Pearson Keller > Northwestern University > Medical Scientist Training Program > cel: 773.608.9185 > email: j-kell...@northwestern.edu > ******************************************* >
