Hi Shun,
This sounds pretty challenging. For a crystal with lattice-translocation disorder the amplitudes are basically all modified by a modulation factor depending on the translocation and the fraction of the crystal involved. Jimin Wang and colleagues used a simple fitting procedure to identify these parameters for both isomorphous and anomalous data (Wang, J., Kamtekar, S., Berman, A. J. & Steitz, T. A. (2005). Acta Cryst. D61, 67–74). It has also been used more recently (for example see https://www.sciencemag.org/content/suppl/2008/02/21/319.5866.1083.DC1/Tanaka...). It is possible that this could help in your case.
Note that for 4.3 A data where anomalous signal is very weak after about 6 A it is not so surprising that automate model-building would fail. You might want to try and find a distantly related structure from the PDB and try to fit domains into your map to evaluate it. You could then use morphing or mr_rosetta to try and improve the model.
All the best
Tom T
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From: [email protected] [[email protected]] on behalf of Shun Liu [[email protected]]
Sent: Tuesday, October 20, 2015 10:35 PM
To: [email protected]
Subject: [phenixbb] Tantalum anomalous signal of a low-resolution SAD dataset with lattice-translocation disorder
Dear Phenix colleagues,
We are working on a Ta6Br14 cluster-SAD dataset (4.3 angstroms) with lattice-translocation disorder (with a total Rmerge of 0.16). Both SHELXC and Xtriage gave the similar positive result about the anomalous signal (See below).
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Resl. Inf. 9.58 7.61 6.65 6.04 5.61 5.27 5.01 4.79 4.61 4.45 4.31
N(data) 1427 1410 1410 1409 1385 1452 1367 1399 1367 1395 1385
76.3 52.1 26.7 13.7 8.7 6.1 5.1 5.0 3.9 2.7 1.8
%Complete 98.8 99.9 100.0 99.9 100.0 100.0 100.0 99.9 99.7 99.6 95.8