Cyclized DTT can look similar to this blob. Of course the sulfur atoms would make one end of the blob more dense than the other.
Dale Tronrud On 07/09/10 05:12, Nick Quade wrote: > Dear CCP4 community, > > I have solved the structure of a protein in complex with DNA. But, > inside the protein there seems to be a ligand binding pocket with some > strong density > (*http://picasaweb.google.de/113264696790316881054/Desktop#). *The > protein was in Tris buffer, with some NaCl, MgCl2 and DTT and > crystallized in Li2SO4 with MES. What could this density be? I can > exclude MES as crystals grown with citrate buffer have the same density. > So I guess it might be something I co-purified or perhaps some > degradation product of the DNA? The electron density in the pictures is > at 1.5sigma. > > Thanks in advance. > > Nick
