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I have a challenge for all those expert model-builders out there: can you beat the machine? It seems these days that everything is automated, and the only decision left for a crystallographer to make is which automation package to use. But has crystallography really been "solved"? Is looking at maps now no more interesting than playing chess, or any of the other once noble pursuits of human beings that we no longer see as "challenging" because someone built a machine that can do the job better than any of us? I think not. But I need your help to prove it. Specifically, the phases in this file: http://bl831.als.lbl.gov/~jamesh/challenge/possible.mtz when fed with the right set of parameters into the best model building package I have available to me actually does converge to the correct structure, with nice low R/Rfree. However, THIS file: http://bl831.als.lbl.gov/~jamesh/challenge/impossible.mtz contains the same amplitudes but very slightly different phases from those in "possible.mtz" above, and this file invariably leads to abysmal failure of every model-building package I have tried. Short of cheating (aka using molecular replacement with the "right ansswer": 3dko), I don't think there is any automated way to arrive at a solved structure from "impossible.mtz". What is interesting about this is how remarkably similar these two maps are. In fact, the correlation coefficient between them is 0.92. And yet, one can be solved automatically, and the other can't. More details can be found on the web page: http://bl831.als.lbl.gov/~jamesh/challenge/ But, my question for the CCP4BB is: Are there any "John Henry"s left out there who can still "beat the machine"? Anyone? -James Holton MAD Scientist