The close approach of the two Zinc atoms may not be too implausible if the charges are being quenched by coordination of the negatively charged residues.
William Ho On Thu, Apr 29, 2010 at 5:38 PM, Daniel Bonsor <[email protected]> wrote: > 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 >
