On Aug 9, 2011, at 10:37 AM, Huiming Li wrote: > Hi All, > > I am working on a Tb binding protein on which I collected anomalous data at > Tb edge of 1.648 A. Each protein is designed to bind one Tb. There are two > copies of the protein in an ASU. I have two questions. First, I am only able > to see one copy of the protein with Tb bound, and no density on the other > copy. Isn't this a bit surprising? I'm assuming that when you say 'density' you're referring to the density around the Tb in both proteins. Radiation damage? One bound Tb and not the other?
> Second, there is one additional peak on each monomer at the site where Fe is > known to bind, and Fe has an edge of 1.739A. At 1.648A, f' and f'' of Fe is > only about 1/5 of Tb. Is it possible Fe also shows some anomalous signal at > Tb edge? Depending on the corectness of the (experimental or model) phases, I've seen Co at the Ir peak and Ir at the Co peak. Use both to cross validate your model (when you get to it) and calculate experimental phases using both (dual SAD or 2wl MAD for each heavy atom). So no it's not surprising. F --------------------------------------------- Francis E. Reyes M.Sc. 215 UCB University of Colorado at Boulder
