Hi all, during refinement of our (membrane protein) structures, basically in all cases the R/Rfree values depend a lot on the low resolution cutoff. Putting the cutoff at lower res (20-50 A) results in substantially higher R/Rfree values (sometimes few percent). For this reason we mostly refine the data from the high-res limit down to 10A or so. I have noticed that this occurs fairly often in the literature, but I don't know if this is a membrane protein related issue or not.
Could it be that the bulk solvent model used in CNS (we refine exclusively with CNS) does not model the situation with membrane proteins, due to the presence of detergents? Or is it related to data collection issues (low-res spots overloaded etc)? Anything else? What could be done to overcome the problem, and to use all the data in refinement? Thanks, Bert Bert van den Berg University of Massachusetts Medical School Program in Molecular Medicine Biotech II, 373 Plantation Street, Suite 115
