Hi All, I am refining a very well ordered structure at 1.45 A and find that after doing just about everything including optimization of weights, etc that there are still areas of positive density residing over S atoms of Met, backbone atoms, etc. I have added hydrogens and used them during refinement as well. The maps are of a high quality and Free R factors are quite good, ~ 17%. Is there anything that can be played with more such as values used in the ADP restraints window to try and achieve a difference map with far fewer areas of significant positive density (all greater then or equal to 4 sigma)? I am not sure exactly what effect the values of distance power, average power, etc will have on refinement. The other option I was thinking of was the scattering table options. I have other structures of this protein that extend to about 1.2. Thanks! Joe ___________________________________________________________ Joseph P. Noel, Ph.D. Investigator, Howard Hughes Medical Institute Professor, The Jack H. Skirball Center for Chemical Biology and Proteomics The Salk Institute for Biological Studies 10010 North Torrey Pines Road La Jolla, CA 92037 USA Phone: (858) 453-4100 extension 1442 Cell: (858) 349-4700 Fax: (858) 597-0855 E-mail: [email protected] Web Site (Salk): http://www.salk.edu/faculty/faculty_details.php?id=37 Web Site (HHMI): http://hhmi.org/research/investigators/noel.html ___________________________________________________________