I just wanted to take a moment to thank all of the respondents to the post. Indeed, my question was more practical in nature since I wanted to "see" the density around the ligand in question. From the first suggestions, I quickly did manage to generate the maps and accomplish my goal (special thanks to Robbie for actually sending me the converted mtz file from the PDB cif entry).
The additional comments have also been highly educational and helpful to further my understanding of some more in-depth crystallography concepts. Thank you, Francisco PS The PDB_REDO (http://www.cmbi.ru.nl/pdb_redo/hf/1hfs/index.html) was indeed a great resource and I'm certain to use it again. Thanks! From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Francisco Hernandez-Guzman Sent: Tuesday, May 22, 2012 9:28 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Calculating ED Maps from structure factor files with no sigma Hello everyone, My apologies if this comes as basic, but I wanted to get the expert's take on whether or not the sigmaF values are required in the calculation of an electron density map. If I look at the standard ED equation, sigma's don't appear to be a requirement but all the scripts that I've looked at do require sigma values. I wanted to calculate the electron density for PDB id: 1HFS but the structure file only lists the Fo's, Fc's and Phases, but no sigmas. Would such structure factor file be considered incomplete? Thank you for your kind explanation. Francisco
