I am solving a structure of an enzyme that I have solved many times before, the only difference is a single mutation in the active site. The crystal grew in basically exact conditions (macroscopically speaking they look different) as the other mutants I had. I scaled the data P 43 21 2 Rsym 0.068. Like all the other data sets I had before. This time however, the initial model has Rfree of about 0.27 and the maps look more like those of a 2.5 - 2.8 structure. My experinence with this enzyme is that I should be looking at around 0.22 or lower Rfree, and pretty clear maps as I saw for my 1.9 structure. Xtriage does not detect any pathologies. I rececked my scaling log file, and it lists the systematic absences for the data. I see some that are not that "weak" for instance : h k l I/sigma 0 0 1 6.0 0 0 2 5.8 0 0 13 7.8 So I am inclined to reprocess my data in P 4 2 2. Are these "symptoms" of a possible wrong space group assignment? Is there something else obvious I am overlooking? Thank you -- Yuri Pompeu