[phenixbb] Autosol help: FOM is great but map is trash

Alex Johnson algejohnson at gmail.com
Thu Feb 18 15:15:15 PST 2021

Hi Phenix team, 

I am attempting to phase a protein structure from SeMet-labeled crystals and have encountered some issues in using Autosol that appear unusual, as they have not been encountered by any members of my group. The short summary is that while I achieved great statistics from beam line collection and Autosol produces solutions with FOM (>0.4) from multiple crystals processed to ~2.4-3.0 A, the output maps are of poor quality and Autobuild can never build with Rfree <0.5. There is only one methionine for the ~30 kDa protein, but the crystals appear to have good anomalous signal with anomalous multiplicity >15 overall and delanon in the inner shell >0.5. There appears to be translational NCS and the dataset can be processed with good statistics in several space groups (P212121, P21212, P2122, etc) but this doesn’t solve the phase problem. The axis drops by half in processing in the P212121 versus P21212 space groups: from one crystal they are 48.37 101.56 110.39 90 90 90 (in P212121) and 101.62 48.35 55.19 90 90 90 (in P21212).

If anyone in the community has encountered similar problems please let me know! I am all ears to any possible solutions and am also installing additional methionine for labeling but unsure whether this will overcome the other issues.


Alex Johnson
Postdoc, Kranzusch lab, Dana-Farber Cancer Institute
algejohnson at gmail.com <mailto:algejohnson at gmail.com>

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