Dear All, something one/some of you might have seen already and might know what it might be/how to analyse:
Material: dimer of Se-Met, Ni-purified, NaCl and NaAc in purification history. I have 4 'waters', 2 each in the same monomer location in a dimer of 2.5A Se-Met structure. They are multiple coordinated - perhaps dist octahedron - and refine down to B=2.0 and show correspondingly strong density. Surrounding protein Bs range from 15 backbone to 37 Arg sidechain First idea of course metal ions. But the distances are odd - 3.1 to 3.7, unusually long for common metal coordination. If I use Na+/Mg++, the Bs still refine down to 4 to 6 K+ B's run up to ~25, Ni++ to 35-40, could be partial occ. Given the charge distribution I doubt Cl- makes sense - it sure looks like a nice place for cation. Not enough space for sul- and fos-fates. No experiments possible, have to deal with what's on hand. Images on web: http://www.ruppweb.org/images/snap.gif http://www.ruppweb.org/images/mystery_ion.gif How common are such large coordination distances in protein/metal coordination and are there any (in silico) analysis tools one could use? Thx, br ----------------------------------------------------------------- Bernhard Rupp 001 (925) 209-7429 +43 (676) 571-0536 [EMAIL PROTECTED] [EMAIL PROTECTED] http://www.ruppweb.org/ ----------------------------------------------------------------- The hard part about playing chicken is to know when to flinch -----------------------------------------------------------------
