Assuming you do this by hand (which I highly recommend), you can add waters as soon as it becomes obvious that they are not something else (particularly missing parts of the protein). It is best to be conservative at start.
Cheers, Robbie From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Dr A.A. Jalan Sent: Monday, April 17, 2017 23:46 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] When should one add solvents Dear All, I have a very elementary question. At what stage of refinement is it appropriate to start adding solvent (water). For example, during refinement of a structure, I was able to build ~ 90% of residues. The density of the remaining residues is not complete. If I take a guess and add residues based on my knowledge of the sequence, the r-free increases. Since I see no further way to improve the maps (any suggestions?), should I start adding water in the hope of improving the overall density and revealing the missing bits. I would really appreciate any inputs. thank you Abhishek
