Dear Alex I take it this density effect is in each of the four molecules? I wonder if the crescent is a series termination effect, although relatively rare in our field. If so what might have caused it? Do you have (radial) gaps in your data set eg due to heavy ice rings? Best wishes, John
Prof John R Helliwell DSc On 24 Feb 2011, at 00:34, Alex Singer <alexander.sin...@utoronto.ca> wrote: > Hi -- I have a high resolution structure (1.6 A) where I'm ready to deposit > except I have > some very strange density, shown in the two pictures here -- sort of a sphere > with a > split cresent around it, falling between molecule A and B His 138 imidazole > rings. The > sphere is modeled as a Cl atom, more for "kicks" because resulting 2Fo-Fc > maps still have > considerable positive difference density throughout the sphere. There are 4 > molecules in > the AU, the imidazole ring of H138 in molecules C and D point into a solvent > channel. > Crystallization conditions are 0.2M Mg Chloride, 0.1M Bis-Tris pH6.5, 25% > PEG3350, > cocrystallized in 2.5mM Glycero-3Phosphocholine and cryoprotected by dipping > in > Paratone_N oil. > > Let me know what you're thoughts are and thank you for your help. > > Alex Singer > > > -- > Dr. Alex Singer > C.H. Best Institute > 112 College St. Room 70 > University of Toronto > Toronto, Canada, M5G 1L6 > 416-978-4033 > <snapshot3.jpg> > <snapshot4.jpg>
