Dear Huiming, as Pavel said, to get a reasonable map you need to collect either higher-resolution data (that you do not have because of your crystal) or low-resolution data. Working with only intermediate-resolution data may give you ugly maps even when your phases are perfect.
As an example, you may look Figs.3 and 7 in Urzhumtsev (1991), Acta Cryst. A47, 794-801 (other examples like this may be suggested). Best regards, Sacha Urzhumtsev ________________________________ De : CCP4 bulletin board [[email protected]] de la part de Huiming Li [[email protected]] Date d'envoi : vendredi 12 août 2011 19:32 À : [email protected] Objet : [ccp4bb] consistently missing eletron density Dear All, I am working on a structure using several sets of data collected between 5 to 6 angstroms. I have never worked with such low resolution before. I was able to get pretty good TFZ between 10 and 16, and the electron density looks overall pretty good. However, among the three data sets I have processed so far, a large chunk of density is missing in all of them around the same area of the protein (largely beta sheet). Is this a manifestation of some intrinsic problems of the crystal, the data, or the protein? Is there a proper procedure I can take to get this density back to make the map a bit more pleasing to view? Thanks, Huiming Li, Ph.D. Immune Disease Institute Children's Hospital Boston
