Re: [phenixbb] [ccp4bb] Tantalum anomalous signal of a low-resolution SAD dataset with lattice-translocation disorder

Hi, difficult to say why it doesn't work. Generally as mentioned already automatic model buildíng will most likely fail at this resolution. However why do you think your sites are wrong? Ta-cluster are regular compounds and the sites should fit with the geometry of the cluster at least. Anyway, molecular replacement using anomalous differences and the cluster as search model might work in that case as well, if direct experimental phasing fails. Cheers Christian Am 21.10.2015 um 05:19 schrieb Shun Liu:

Dear CCP4 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).

------------------------------------------------------------------------------------------------- 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 11.67 9.67 6.12 3.73 2.50 1.59 1.21 0.99 0.84 0.79 0.68 ------------------------------------------------------------------------------------------------ unused: - 49.7669 [ 0/29 ] bin 1: 49.7669 - 9.2629 [3086/3100] 0.8212 bin 2: 9.2629 - 7.3599 [3031/3031] 0.7689 bin 3: 7.3599 - 6.4318 [3073/3073] 0.5380 bin 4: 6.4318 - 5.8447 [3071/3075] 0.2933 bin 5: 5.8447 - 5.4263 [3054/3054] 0.1230 bin 6: 5.4263 - 5.1067 [3070/3071] 0.0363 bin 7: 5.1067 - 4.8512 [3038/3039] 0.0126 bin 8: 4.8512 - 4.6402 [3028/3048] 0.0074 bin 9: 4.6402 - 4.4617 [2955/3037] 0.0021 bin 10: 4.4617 - 4.3078 [2730/3059] 0.0000 unused: 4.3078 - [ 0/0 ] -------------------------------------------------------------------------------------------------- The Tantalum sites and the initial map seem ambiguous, with which automatic model-building failed. I am wondering whether the lattice-translocation disorder of the dataset impacts the reliability of the anomalous signal, tantalum sites and the initial map. If it does, how can we decrease its impact? If it doesn't, is it possible to find the accurate Ta sites and generate an interpretable map suitable for model-building with this dataset? (After all, it has been reported that Ta sites can be found at 6A resolution.)

Any suggestion and comment will be highly appreciated!

Best, Shun