Dear Daniel Is the omit map for the model with and without the zinc ions possible to confirm its existence? I am curious. What is the resolution of dataset?
stephen Quoting Daniel Bonsor <[email protected]>: > Hello again > > I currently have some unexplained density in my structure. As you can > hopefully see from the images (see file), the density is dumbbell shaped. > Whatever it is, it is coordinated by Asp and Glu residues. To me it looks > like each lobe is a ring structure. > > > The crystallization condition was: > 6.5% PEG 8K, 10mM ZnSO4, 100mM sodium cacodylate pH 6.5, 100mM Am2SO4, 1% > glycerol, with 20% glycerol as cryo. > Protein was originally in 50mM Tris, 50mM NaCl pH 7.5. > > > I originally placed a single Zn at the center of each lobe. Though after > refmac, the Zn was displaced to one side. Two zincs in each dumbbell may have > worked, but I am dubious about two zinc atoms being 4A apart and there is > still some unexplained density. Are there any possible cyclization reactions > of Tris, cacodylate or glycerol may have undergone to explain the density? Or > is it simply a highly ordered water network? Or is there some other > explanation? > > Thanks in advance > > Dan > -- Dr. Stephen Sin-Yin Chui Research Assistant Professor, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China. Tel: 22415814 (Office), 22415818 (X-ray Diffraction Laboratory)
