goodsignal.tar.gz

badsignal.tar.gz

overlaps.tar.gz

decay.tar.gz

icy.tar.gz

dataset    fpp     solve  shelxs  shelxd  hyss  cheat   CC
goodsignal 3.0      8/8    8/28    8/11   8/8    8/8   0.82
badsignal  0.8      0/4    1/21    0/11   0/0    7/8   0.49
overlaps   3.0      8/8    8/28    8/11   8/8    8/8   0.77
decay      4.0-0.0  0/8    3/40    0/11   0/8    7/8   0.42
icy        3.0      8/8    8/22    8/11   8/8    8/8   0.72

• The data set "goodsignal" corresponds to a perfectly adequate phasing signal with no overlap problems and no radiation damage.
• The "badsignal" data set is exactly the same, with the single exception that the f" signal has been reduced to 0.8 electrons. Similar to the difference between Se SAD and Sulphur SAD.
• The "overlaps" data set is exactly the same as the "goodsignal" data set, but with the crystal orientation changed so that the c axis is nearly perpendicular to the rotation axis and overlaps are unavoidable.
• The "decay" data set is also the same as the "goodsignal" data set, but the f" value is decaying exponentially from the beginning to the end. The average f" value is still 3.0.
• The "icy" data set is exactly the same as the "goodsignal" data set, except that it has ice rings.

• all data sets require the keyword "SEPARATION 0.5 0.5 CLOSE" to be added to the mosflm script. You get the number "0.5" because if you look at the spots in a graphic viewer, you can see that they are about 5 pixels wide, and the pixels on this detector are 0.1 mm. You can type this in on any of the command prompts in Wedger Elves. Alternately, you can put this text into a file and provide the filename on the Wedger Elves command line.
• The "overlaps" data set also requires the "POSTREF ADD 30" keyword to stabilize the refinement in mosflm because so many spots are overalpped. Wedger Elves will do this automatically after the refinement fails a few times.
• The "icy" data set requires that the ice ring resolution ranges be eliminated from processing. If you don't do this, then truncate will crash. Truncate will also crash after eliminating the ice rings because of the "gaps" it introduces in the data. You must override the default number of bins used by truncate to get around this. You have to add "RANGES 10" to the truncate section of the merge.com scripts generated by Wedger and Scaler Elves.
• The best indicator of "wether or not you can solve the structure" is the "Correlation coefficients for anomalous differences" table in the scala log. This is a new feature in CCP4 5.x and above. CC values of 0.3 or more indicate a good anomalous signal and a high likelihood that some heavy-atom finding program will work. CC values around 0 indicate hopeless data. Notice that although the anomalous differences are strong in the "decay" data set (on average, they are as big as the "goodsignal" data set), the CC values in this chart are near 0 because the differences are changing over time.