Dear all, thanks a lot for the many replies suggesting me what to put in my "misterious" density. Molecules that have been suggested are: acetate, Mg ion with waters, bicarbonate or nitrate, sulphate, borate, glycerol, tris, alternative conformation of the Arg side chain, waters. I have to say that, as you've noticed, the resolution is only 2.6, so it'll be hard to conclude something beyond reasonable doubts. What I'm doing is, as Roger Rowlett and David Borhani suggested, calculating the maps by omitting the waters, and deciding upon the shape of the density I see there, trying than to fit different molecules.
In doubt, it'd seem reasonable to me to place one of the molecule of the crystallization conditions. At the moment, it seems that glycerol could fit nicely. I also have to apologize for the large attachment. I'm sorry I didn't notice it was so large (I have to admit, I just sent what Wincoot wrote out! ;-)). Next time I'll be surely posting the image to some website. Thanks again, all the best, S -- Sebastiano Pasqualato, PhD IFOM-IEO Campus Dipartimento di Oncologia Sperimentale Istituto Europeo di Oncologia via Adamello, 16 20139 - Milano Italy tel +39 02 9437 5094 fax +39 02 574 303 310
