Hi, I'm doing a joint X-ray neutron refinement in Phenix and have run into some behaviour that puzzles me. I had not been paying any attention to the use or non-use of anomalous signal in the neutron dataset, as This is what I get if I let phenix.refine itself decide whether or not to use anomalous data: ================================= Neutron data ================================ F-obs: neutron.mtz:FO,SIGFO,DANO,SIGDANO,ISYM Miller array info: neutron.mtz:FO,SIGFO,DANO,SIGDANO,ISYM Observation type: xray.reconstructed_amplitude Type of data: double, size=16672 Type of sigmas: double, size=16672 Number of Miller indices: 16672 Anomalous flag: True Unit cell: (removed) Space group: P 21 21 21 (No. 19) Systematic absences: 0 Centric reflections: 1258 Resolution range: 29.22 1.89826 Completeness in resolution range: 0.785008 Completeness with d_max=infinity: 0.78486 Bijvoet pairs: 6832 Lone Bijvoet mates: 1750 Anomalous signal: 0.0876 Number of F-obs in resolution range: 16672 Number of F-obs<0 (these reflections will be rejected): 0 Number of F-obs=0 (these reflections will be used in refinement): 0 Refinement resolution range: d_max = 29.2200 d_min = 1.8983 and this is what I get if I forcibly switch off use of anomalous data in the phenix.refine GUI: ================================= Neutron data ================================ F-obs: neutron.mtz:FO,SIGFO,DANO,SIGDANO,ISYM Miller array info: neutron.mtz:FO,SIGFO,DANO,SIGDANO,ISYM Observation type: xray.reconstructed_amplitude Type of data: double, size=16672 Type of sigmas: double, size=16672 Number of Miller indices: 16672 Anomalous flag: True Unit cell: (removed) Space group: P 21 21 21 (No. 19) Systematic absences: 0 Centric reflections: 1258 Resolution range: 29.22 1.89826 Completeness in resolution range: 0.785008 Completeness with d_max=infinity: 0.78486 Bijvoet pairs: 6832 Lone Bijvoet mates: 1750 Anomalous signal: 0.0876 force_anomalous_flag_to_be_equal_to=False Reducing data to non-anomalous array. R-linear = sum(abs(data - mean(data))) / sum(abs(data)) R-square = sum((data - mean(data))**2) / sum(data**2) In these sums single measurements are excluded. Redundancy Mean Mean Min Max Mean R-linear R-square unused: - 29.2234 bin 1: 29.2234 - 4.0863 1 2 1.699 0.0240 0.0011 bin 2: 4.0863 - 3.2448 1 2 1.793 0.0302 0.0022 bin 3: 3.2448 - 2.8350 1 2 1.800 0.0417 0.0041 bin 4: 2.8350 - 2.5760 1 2 1.764 0.0486 0.0054 bin 5: 2.5760 - 2.3914 1 2 1.745 0.0505 0.0051 bin 6: 2.3914 - 2.2505 1 2 1.717 0.0513 0.0051 bin 7: 2.2505 - 2.1378 1 2 1.658 0.0533 0.0056 bin 8: 2.1378 - 2.0448 1 2 1.614 0.0611 0.0074 bin 9: 2.0448 - 1.9661 1 2 1.575 0.0634 0.0075 bin 10: 1.9661 - 1.8983 1 2 1.485 0.0736 0.0097 unused: 1.8983 - Fobs statistics after all cutoffs applied: Miller array info: None Observation type: xray.amplitude Type of data: double, size=9840 Type of sigmas: double, size=9840 Number of Miller indices: 9840 Anomalous flag: False Unit cell: (removed) Space group: P 21 21 21 (No. 19) Systematic absences: 0 Centric reflections: 1258 Resolution range: 29.22 1.89826 Completeness in resolution range: 0.855801 Completeness with d_max=infinity: 0.855503 What's going on here? If I let phenix.refine decide automatically, it looks like it's reading in F+ and F- separately and regarding them as independent in the refinement. If I force "no anomalous" it merges them. However I can't work out whether in either case it has actually read FOBS instead of the Friedel mates. According to the SCALA manual the I+ and I- columns will always be written out even if the keyword ANOMALOUS OFF is used, so this is a potential pitfall for many. In addition, phenix.refine seems to identify the neutron data first as xray.reconstructed_amplitude then as xray.amplitude even though the data are explicitly defined as neutron data in the GUI. I can send more information if required! Thanks Derek ________________________________________________________________________ Derek Logan tel: +46 46 222 1443 Associate Professor mob: +46 76 8585 707 Dept. of Biochemistry and Structural Biology www.cmps.lu.sehttp://www.cmps.lu.se Centre for Molecular Protein Science www.maxlab.lu.se/node/307http://www.maxlab.lu.se/node/307 Lund University, Box 124, 221 00 Lund, Sweden www.saromics.comhttp://www.saromics.com