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? 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?
Thank you, Huiming Li, Ph.D. Immune Disease Institute Children's Hospital Boston Harvard Medical School Boston, MA 02115