Hi, I still have little experience in the refinement of protein structures. So, I have some (basic) doubts that I would like you to help me please. 1) I have a metal coordinated to a cofactor in the active center of my protein structure. The initial solution provided by phaser/autobuilding already contained the metal+cofactor modelled in the density but with zero occupancy. Then I created all the necessary restraints and cif files with phenix_ready_set and did two cycles of model building/phenix refinement. The refined structures always contained zero occupancy for those atoms. My question is: should I manually change the occupancy for the metal+cofactor to 1? I thought this would be made automatically by phenix because I selected the option “occupancies” and “individual B-factors” in the refinement strategy… 2) When manually placing waters in the density with coot, what is the maximum value of B-factor that is acceptable for a water? I am asking that because I have some water molecules with weak density and consequently B-factors between 45 and 55 but that are involved in interactions with other molecules. Is it better to keep those waters or remove them? Best regards, Alexandra