I had a case of P 41 21 2 at 2.5A that had a perfect SAD map for iodine soaked data. However, the R statistics were stuck in the mid 30's with over 2/3 of the asymmetric unit built (the other 1/3 at the N/C termini and internal loop region remained disordered). Though it didn't test positive for twinning, I considered perfect twinning and scaled it to P41 with now two molecules per asu. A few (maybe 2-3) residues could be built at the N/C termini and the statistics dropped into the mid 20's with NCS (due to lower symmetry). I have yet to find a twinning test that can assess perfect twinning. So you might want to consider it. FR On Apr 27, 2009, at 6:30 AM, vennila Natesan wrote:
Dear Tom
Thankyou for your kind reply.I checked my data witn phenix.xtriage and there are good anomalous signal (>0.05)in all the resolution shells. Also the systematic absences show it is P43212.Still i couldnt solve using phenix.Where is the thing going wrong? Xtriage results also showed no twinning.
My previous message: I am using phenix1.4-4 version. In autosol, got the score of 10.24 for one iodine soaked data. FOM:0.27 and only 54 residues ( that too wrongly) were built out of 129.(CC=0.4), R=0.49 and Rfree=0.574. Regrading the data quality, Rsym:0.0448, Ranom:0.055, Resln:25.0-2.6A Spacegroup is P43212, completeness:99.4%, Multiplicity:11.7, anomalos signal is 1.52 at lowest resoln and higher in high resolution shells.
What might be reason for not able to solve this structure?
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