Hi, Here is a result (attached) of analyzing over 2000 Structural Genomics structures. At ~2 A resolution, you would roughly expect 1 water for every two residues.
Thanks Abhinav Stanford Synchrotron Radiation Laboratory Joint Center for Structural Genomics Mail Stop 99 Phone: (650) 926-2992 Fax: (650) 926-3292 -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Sabini, Elisabetta Sent: Wednesday, August 15, 2007 10:35 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] "Dry" structures Dear all, what does it mean when a structure doesn't have many water molecules? I have a 2.3A data set, 2 molecules in the AU (260 residues each), space group C2221 - I haven't finished my water search but I don't seem to have more than 20-30 obvious/good water molecules. The Rfac/Rfree are 22/30%, the protein is modeled and the ligands are in. I collected the data at APS SERCAT ID-22. Did I have a dry crystal (!!) or did the beamline dried it up?! How many water molecules should I expect at this resolution? Also, what does it mean when a strong peak in the Fobs-Fc doesn't have the corresponding 2Fobs-Fc map covering it even at very low sigma? Thank you! Eli :o) PS: I have attached the statistics for the data set from XDS -- Elisabetta Sabini, Ph.D. Research Assistant Professor University of Illinois at Chicago Department of Biochemistry and Molecular Genetics Molecular Biology Research Building, Rm. 1108 900 South Ashland Avenue Chicago, IL 60607 U.S.A. Tel: (312) 996-6299 Fax: (312) 355-4535 E-mail: [EMAIL PROTECTED]
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